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  • 1. Bi, D.
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT), China.
    Gao, P.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT), China.
    Grätzel, M.
    Hagfeldt, A.
    Facile synthesized organic hole transporting material for perovskite solar cell with efficiency of 19.8%2016In: Nano Energy, ISSN 2211-2855, Vol. 23, p. 138-144Article in journal (Refereed)
    Abstract [en]

    The exploration of alternative molecular hole-transporting materials (HTMs) specifically for high performance perovskite solar cells (PSCs) is a relatively recent research area. Aiming for further increasing the 'efficiency-cost ratio' of PSCs, we developed a spiro[fluorene-9,9'-xanthene] based HTM (X59) via two-step synthesis from commercial precursors for perovskite solar cells (PSCs) that works as effectively as the well-known HTM-Spiro-OMeTAD-based device under the same conditions. The molecular structure was analyzed by X-ray crystallography indicating a similar packing regime as for Spiro-OMeTAD. An impressive PCE of 19.8% was achieved by using X59 as HTM in PSC, which can compete with the record PCE of 20.8% by using the state-of-the-art-HTM Spiro-OMeTAD (Tress et al., 2016) [1]. The optimized devices employing X59 as HTM exhibited minimized hysteresis, excellent reproducibility and reasonable stability under dark and dry conditions. The present finding highlights the potential of spiro-type HTM for high performance PSCs and paves the way to a much deceased fabrication cost for potential commercialization of perovskite solar panels.

  • 2.
    Bo, Xu
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Advanced Organic Hole Transport Materials for Solution-Processed Photovoltaic Devices2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Solution-processable photovoltaic devices (PVs), such as perovskite solar cells (PSCs) and solid-state dye-sensitized solar cells (sDSCs) show great potential to replace the conventional silicon-based solar cells for achieving low-cost and large-area solar electrical energy generation in the near future, due to their easy manufacture and high efficiency. Organic hole transport materials (HTMs) play important roles in both PSCs and sDSCs, and thereby can well facilitate the hole separation and transportation, for obtaining high performance solar cells.

    The studies in this thesis aimed to develop advanced small-molecule organic HTMs with low-cost, high hole mobility and conductivity for the achievement of highly efficient, stable and reproducible sDSCs and PSCs. In order to achieve these objectives, two different strategies were utilized in this thesis: the development of new generation HTMs with simple synthetic routes and the introduction of cost-effective p-type dopants to control the charge transport properties of HTMs.

    In Chapter 1 and Chapter 2, a general introduction of the solution-processed sDSCs and PSCs, as well as the characterization methods that are used in this thesis were presented.

    In Chapter 3 and Chapter 4, a series of novel triphenylamine- and carbazole- based HTMs with different oxidation potential, hole mobility, conductivity and molecular size were designed and synthesized, and then systematically applied and investigated in sDSCs and PSCs.

    In Chapter 5, two low-cost and colorless p-type dopants AgTFSI and TeCA were introduced for the organic HTM-Spiro-OMeTAD, which can significantly increase the conductivity of the Spiro-OMeTAD films. The doping effects on the influence of sDSC and PSC device performances were also systematically investigated.

  • 3.
    Cheng, Ming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Chen, Cheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Fuguo
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    A novel phenoxazine-based hole transport material for efficient perovskite solar cell2015In: Journal of Energy Challenges and Mechanics, ISSN 2095-4956, E-ISSN 2056-9386, Vol. 24, no 6, p. 698-706Article in journal (Refereed)
    Abstract [en]

    Based on the previous research work in our laboratory, we have designed and synthesized a small-molecule, hole transport material (HTM) POZ6-2 using phenoxazine (POZ) as central unit and dicyanovinyl units as electron-withdrawing terminal groups. Through the introduction of a 2-ethyl-hexyl bulky chain into the POZ core unit, POZ6-2 exhibits good solubility in organic solvents. In addition, POZ6-2 possesses appropriate energy levels in combination with a high hole mobility and conductivity in its pristine form. Therefore, it can readily be used as a dopant-free HTM in perovskite solar cells (PSCs) and a conversion efficiency of 10.3% was obtained. The conductivity of the POZ6-2 layer can be markedly enhanced via doping in combination with typical additives, such as 4-tert-butylpyridine (TBP) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). Correspondingly, the efficiency of the PSCs was further improved to 12.3% using doping strategies. Under the same conditions, reference devices based on the well-known HTM Spiro-OMeTAD show an efficiency of 12.8%.

  • 4.
    Cheng, Ming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Chen, C.
    Yang, X.
    Zhang, F.
    Tan, Q.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Phenoxazine-based small molecule material for efficient perovskite solar cells and bulk heterojunction organic solar cells2015In: Advanced Energy Materials, ISSN 1614-6832, Vol. 5, no 8, article id 1401720Article in journal (Refereed)
    Abstract [en]

    The phenoxazine-based acceptor-donor-acceptor structured small-molecule material M1 is used either as a hole-transport material in (CH<inf>3</inf>NH<inf>3</inf>)PbI<inf>3</inf>-perovskite-based solar cells or as photoactive donor material in bulk heterojunction organic solar cells. Excellent power conversion efficiencies of 13.2% and 6.9% are achieved in these two types of photovoltaic devices, respectively.

  • 5.
    Hua, Yong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Chen, Hong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    High conductivity Ag-based metal organic complexes as dopant-free hole-transport materials for perovskite solar cells with high fill factors2016In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 7, no 4, p. 2633-2638Article in journal (Refereed)
    Abstract [en]

    Hole-transport materials (HTMs) play an important role as hole scavenger materials in the most efficient perovskite solar cells (PSCs). Here, for the first time, two Ag-based metal organic complexes (HA1 and HA2) are employed as a new class of dopant-free hole-transport material for application in PSCs. These HTMs show excellent conductivity and hole-transport mobility. Consequently, the devices based on these two HTMs exhibit unusually high fill factors of 0.76 for HA1 and 0.78 for HA2, which are significantly higher than that obtained using spiro-OMeTAD (0.69). The cell based on HA1-HTM in its pristine form achieved a high power conversion efficiency of 11.98% under air conditions, which is comparable to the PCE of the cell employing the well-known doped spiro-MeOTAD (12.27%) under the same conditions. More importantly, their facile synthesis and purification without using column chromatography makes these new silver-based HTMs highly promising for future commercial applications of PSCs. These results provide a new way to develop more low-cost and high conductivity metal-complex based HTMs for efficient PSCs.

  • 6.
    Hua, Yong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, J.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, E. M. J.
    Sveinbjörnsson, K.
    Aitola, K.
    Boschloo, G.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT), China.
    Facile synthesis of fluorene-based hole transport materials for highly efficient perovskite solar cells and solid-state dye-sensitized solar cells2016In: Nano Energy, ISSN 2211-2855, Vol. 26, p. 108-113Article in journal (Refereed)
    Abstract [en]

    Two novel low-cost fluorene-based hole transport materials (HTMs) HT1 and HT2 as alternatives to the expensive HTM Spiro-OMeTAD have been designed and synthesized for the application in perovskite solar cells (PSCs) and solid-state dye-sensitized solar cell (ssDSCs). The two HTMs were prepared through a facile two-step reaction from cheap starting material and with a total yield higher than 90%. These HTMs exhibit good solubility and charge-transport ability. PSCs based on HT2 achieved power conversion efficiency (PCE) of 18.04% under air conditions, which is comparable to that of the cell employing the commonly used Spiro-OMeTAD (18.27%), while HT1-based cell showed a slightly worse performance with a PCE of 17.18%. For ssDSCs, the HT2-based device yielded a PCE of 6.35%, which is also comparable to that of a cell fabricated based on Spiro-OMeTAD (6.36%). We found that the larger dimensional structure and molecular weight of HT2 enable better photovoltaic performance than that of the smaller one HT1. These results show that easily synthesized fluorene-based HTMs have great potential to replace the expensive Spiro-OMeTAD for both PSCs and ssDSCs.

  • 7.
    Huang, Jing
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Yuan, Chunze
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Chen, Hong
    Sun, Junliang
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Improved Performance of Colloidal CdSe Quantum Dot-Sensitized Solar Cells by Hybrid Passivation2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 21, p. 18808-18815Article in journal (Refereed)
    Abstract [en]

    A hybrid passivation strategy is employed to modify the surface of colloidal CdSe quantum dots (QDs) for quantum dot-sensitized solar cells (QDSCs), by using mercaptopropionic acid (MPA) and iodide anions through a ligand exchange reaction in solution. This is found to be an effective way to improve the performance of QDSCs based on colloidal QDs. The results show that MPA can increase the coverage of the QDs on TiO2 electrodes and facilitate the hole extraction from the photoxidized QDs, and simultaneously, that the iodide anions can remedy the surface defects of the CdSe QDs and thus reduce the recombination loss in the device. This hybrid passivation treatment leads to a significant enhancement of the power conversion efficiency of the QDSCs by 41%. Furthermore, an optimal ratio of iodide ions to MPA was determined for favorable hybrid passivation; results show that excessive iodine anions are detrimental to the loading of the QDs. This study demonstrates that the improvement in QDSC performance can be realized by using a combination of different functional ligands to passivate the QDs, and that ligand exchange in solution effective approach to introduce can be an different ligands.

  • 8.
    Li, Fusheng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fan, Ke
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Gabrielsson, Erik
    Daniel, Quentin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Li, Lin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian, China.
    Organic Dye-Sensitized Tandem Photoelectrochemical Cell for Light Driven Total Water Splitting2015In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, no 28, p. 9153-9159Article in journal (Refereed)
    Abstract [en]

    Light driven water splitting was achieved by a tandem dye-sensitized photoelectrochemical cell with two photoactive electrodes. The photoanode is constituted by an organic dye L0 as photosensitizer and a molecular complex Ru1 as water oxidation catalyst on meso-porous TiO2, while the photocathode is constructed with an organic dye P1 as photoabsorber and a molecular complex Col as hydrogen generation catalyst on nanostructured NiO. By combining the photocathode and the photoanode, this tandem DS-PEC cell can split water by visible light under neutral pH conditions without applying any bias.

  • 9.
    Liu, Peng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. kTH.
    Sharmoukh, Walid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Li, Yuanyuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Boschloo, Gerrit
    Uppsala University.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Dalian University of Technology (DUT), Dalian, China.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Novel and Stable D-A-π-A Dyes for Efficient Solid-state Dye-sensitized Solar Cells2017In: ACS Omega, Vol. 2, no 5, p. 1812-1819Article in journal (Refereed)
    Abstract [en]

    Two novel organic donor–acceptor−π–acceptor sensitizers, W7 and W8, have been applied in efficient solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9′-spirobifluorene (Spiro-OMeTAD) as hole-transport material (HTM), an excellent power conversion efficiency of 6.9% was recorded for W7, together with an excellent photocurrent of 10.51 mA cm–2 and a high open-circuit voltage of 880 mV under standard AM 1.5 G illumination (100 mW cm–2). The solid-state solar cells based on W8 showed an efficiency of 5.2%, with a good photocurrent of 9.55 mA cm–2 and an open-circuit voltage of 870 mV. Compared to that of the well-known WS2 sensitizer, the results show that the performance of the ssDSSC devices can be significantly improved by introducing triphenylamine moiety into their structure. In addition, results of photoinduced absorption spectroscopy show efficient dye regeneration for W7- and W8-based devices. A higher hole conductivity of the W7/HTM and W8/HTM layers compared to that of the WS2/HTM layer was observed, indicating an efficient charge transfer at the interfaces. The results obtained offer insights into the design of reliable and highly efficient ssDSSCs for large-scale applications.

  • 10.
    Liu, Peng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. kTH.
    Wang, Linqin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Karlsson, Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hao, Yan
    Uppsala University.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Boschloo, Gerrit
    Uppsala University.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Dalian University of Technology (DUT), Dalian, China.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Molecular Engineering of D-π-A Type of Blue Dyes for Highly Efficient Solid State Dye Sensitized Solar Cells by Co-Sensitization2017In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501Article in journal (Refereed)
  • 11.
    Liu, Peng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Aitola, K.
    Sveinbjörnsson, K.
    Zhang, J.
    Boschloo, G.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Design, synthesis and application of a π-conjugated, non-spiro molecular alternative as hole-transport material for highly efficient dye-sensitized solar cells and perovskite solar cells2017In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 344, p. 11-14Article in journal (Refereed)
    Abstract [en]

    Two low-cost, easily synthesized π-conjugated molecules have been applied as hole-transport materials (HTMs) for solid state dye-sensitized solar cells (ssDSSCs) and perovskite solar cells (PSCs). For X1-based devices, high power conversion efficiencies (PCEs) of 5.8% and 14.4% in ssDSSCs and PSCs has been demonstrated. For X14-based devices, PCEs were improved to 6.1% and 16.4% in ssDSCs and PSCs, respectively.

  • 12.
    Liu, Peng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Karlsson, Karl Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Zhang, Jinbao
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    The combination of a new organic D-pi-A dye with different organic hole-transport materials for efficient solid-state dye-sensitized solar cells2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 8, p. 4420-4427Article in journal (Refereed)
    Abstract [en]

    A new organic donor-pi-acceptor sensitizer MKA253 has been applied for highly efficient solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2',7,7'-tetrakis(N,N-di-pi-methoxyphenyl-amine) 9,9'-spirobifluorene (Spiro-OMeTAD) as the hole transport material (HTM), an excellent power conversion efficiency of 6.1% was recorded together with a high short-circuit current of 12.4 mA cm(-2) under standard AM 1.5G illumination (100 mW cm(-2)). Different combinations of dyes and HTMs have also been investigated in the ssDSSC device. The results showed that small molecule HTM based devices suffer from comparably high electron recombination losses, thus causing low open-circuit voltage. In addition, photo-induced absorption (PIA) spectroscopy showed that the small-molecule HTMs lead to more efficient dye regeneration in comparison with Spiro-OMeTAD, despite a lower thermodynamic driving force. The results of this study also show that optimized energy levels for the dye-HTMs could be a vital factor for highly efficient ssDSSCs.

  • 13.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fischer, Andreas I.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Structure and function relationships in alkylammonium lead(II) iodide solar cells2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 17, p. 9201-9207Article in journal (Refereed)
    Abstract [en]

    Alkylammonium lead(ii) iodide materials (APbI<inf>3</inf>), based on the general formula of CH<inf>3</inf>-(CH<inf>2</inf>)<inf>n</inf>-NH<inf>3</inf>PbI<inf>3</inf>, may lead to a monumental leap in developing affordable photovoltaics. Herein, we correlate the structure and function relationships of alkylammonium lead(ii) iodide in solar cells. We investigated changes in the structure of APbI<inf>3</inf> materials by varying the alkylammonium cations in their structure. As the size of the alkylammonium cation increased, the crystallographic unit cell increased in size and yielded lower symmetry crystals. High symmetry materials, those with cubic symmetry, showed the highest conductivity, the smallest bandgap, and produced the best performing solar cells. Structural changes were investigated by X-ray crystallography, X-ray powder diffraction, and Raman scattering.

  • 14.
    Sheibani, Esmaeil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Univ Isfahan, Iran.
    Zhang, Lei
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Mijangos, Edgar
    Boschloo, Gerrit
    Hagfeldt, Anders
    Hammarstrom, Leif
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Uppsala University, Sweden.
    A study of oligothiophene-acceptor dyes in p-type dye-sensitized solar cells2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 22, p. 18165-18177Article in journal (Refereed)
    Abstract [en]

    Two new dyes, E1 and E2, equipped with triphenylamine as the electron donor, oligothiophene as the linker and different electron acceptor groups, have been designed and synthesized as photosensitizers for p-type dye-sensitized solar cells (p-DSCs). A systematic study of the effect of molecular structures on the observed photophysical properties, the electron/hole recombination process, the overall performance and the interfacial charge separation was carried out. Transient absorption spectroscopy (TAS) shows that the E1 dye with a napthoilene-1,2-benzimidazole (NBI) unit as the acceptor has a longer lifetime in the reduced state than the E2 dye with a malononitrile subunit on the NiO surface.

  • 15.
    Tian, Haining
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Oscarsson, Johan
    Gabrielsson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Eriksson, Susanna K.
    Lindblad, Rebecka
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Hao, Yan
    Boschloo, Gerrit
    Johansson, Erik M. J.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hagfeldt, Anders
    Rensmo, Håkan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Enhancement of p-Type Dye-Sensitized Solar Cell Performance by Supramolecular Assembly of Electron Donor and Acceptor2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 4282-Article in journal (Refereed)
    Abstract [en]

    Supramolecular interactions based on porphyrin and fullerene derivatives were successfully adopted to improve the photovoltaic performance of p-type dye-sensitized solar cells (DSCs). Photoelectron spectroscopy (PES) measurements suggest a change in binding configuration of ZnTCPP after co-sensitization with C60PPy, which could be ascribed to supramolecular interaction between ZnTCPP and C60PPy. The performance of the ZnTCPP/C60PPy-based p-type DSC has been increased by a factor of 4 in comparison with the DSC with the ZnTCPP alone. At 560 nm, the IPCE value of DSCs based on ZnTCPP/C60PPy was a factor of 10 greater than that generated by ZnTCPP-based DSCs. The influence of different electrolytes on charge extraction and electron lifetime was investigated and showed that the enhanced V-oc from the Co2+/(3+)(dtbp)(3)-based device is due to the positive E-F shift of NiO.

  • 16.
    Tian, Haining
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Soto, Andrea
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hagfeldt, Anders
    Fabregat-Santiago, Francisco
    Mora-Sero, Ivan
    Kang, Yong Soo
    Bisquert, Juan
    Barea, Eva M.
    Effect of the chromophores structures on the performance of solid-state dye sensitized solar cells2014In: Nano, ISSN 1793-2920, Vol. 9, no 5, p. 1440005-Article in journal (Refereed)
    Abstract [en]

    The er effect of metal-free chromophores on dye-sensitized solar cell performance is investigated. Solid state dye-sensitized solar cells (ssDSCs) using dirfferent molecular sensitizers based on tri-phenylamine (TPA) with thiophene linkers and different alkyl chain in the donor unit have been characterized using impedance spectroscopy (IS). We show that different molecular structures play a fundamental role on solar cell performance, by the effect produced on TiO2 conduction band position and in the recombination rate. Dye structure and its electronic properties are the main factors that control the recombination, the capacitance and the efficiency of the cells. A clear trend between the performance of the cell and the optimization level of the blocking effect of the dye structure has been identified in the solid state solar cells with Spiro-OMeTAD hole conductor.

  • 17.
    Tian, Haining
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Chen, Hong
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Solid-State Perovskite-Sensitized p-Type Mesoporous Nickel Oxide Solar Cells2014In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 8, p. 2150-2153Article in journal (Refereed)
    Abstract [en]

    ,Perovskite has been adopted as photosensitizer to develop solid state p-type mesoporous nickel oxide (NiO) dye-sensitized solar cells (DSCs) employing PCBM as electron conductor. The optimal device achieved an efficiency of 1.5% with an impressive open circuit voltage of more than 800 mV, which is the record of solar cell based on p-type mesoporous NiO electrode. This result shows the potential for building highly efficient p-type NiO solar cells as stand-alone device.

  • 18.
    Wang, Linqin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Sheibani, Esmaeil
    Guo, Yu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Zhang, Wei
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Liu, Peng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol, State Key Lab Fine Chem, Inst Artificial Photosynth, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China.
    Impact of Linking Topology on the Properties of Carbazole-Based Hole-Transport Materials and their Application in Solid-State Mesoscopic Solar Cells2019In: SOLAR RRL, ISSN 2367-198X, article id 1900196Article in journal (Refereed)
    Abstract [en]

    Carbazole is a promising core for the molecular design of hole-transport materials (HTMs) for solid-state mesoscopic solar cells (ssMSCs), such as solid-state dye-sensitized solar cells (ssDSSCs) and perovskite solar cells (PSCs) due to its low cost and excellent optoelectronic properties of its derivatives. Although carbazole-based HTMs are intensely investigated in ssMSCs and promising device performance is demonstrated, the fundamental understanding of the impact of linking topology on the properties of carbazole-based HTMs is lacking. Herein, the effect of the linking topology on the optical and electronic properties of a series of carbazole-based HTMs with 2,7-substitution and 3,6-substitution is systematically investigated. The results demonstrate that the 2,7-substituted carbazole-based HTMs display higher hole mobility and conductivity among this series of analogous molecules, thereby exhibiting better device performance. In addition, the conductivity of the HTMs is improved after light treatment, which explains the commonly observed light-soaking phenomenon of ssMSCs in general. All these carbazole-based HTMs are successfully applied in ssMSCs and one of the HTMs X50-based devices yield a promising efficiency of 6.8% and 19.2% in ssDSSCs and PSCs, respectively. This study provides guidance for the molecular design of effective carbazole-based HTMs for high-performance ssMSCs and related electronic devices.

  • 19.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Bi, Dongqin
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Graetzel, Michael
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT), China.
    A low-cost spiro[fluorene-9,9 '-xanthene]-based hole transport material for highly efficient solid-state dye-sensitized solar cells and perovskite solar cells2016In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 3, p. 873-877Article in journal (Refereed)
    Abstract [en]

    A low-cost spiro[fluorene-9,9'-xanthene] (SFX) based organic hole transport material (HTM) termed X60 was designed and synthesized using a two-step synthetic route. Devices with X60 as HTM showed high power conversion efficiencies (PCEs) amounting to 7.30% in solid-state dye-sensitized solar cells (ssDSCs) and 19.84% in perovskite solar cells (PSCs), under 100 mW cm(-2) AM1.5G solar illumination. To the best of our knowledge, this is the first example of an easily synthesized spiro-structured HTM that shows comparable performance with respect to the well-known HTM Spiro-OMeTAD in both ssDSCs and PSCs. Furthermore, the facile synthesis of X60 from commercially available starting materials makes this HTM very promising for large-scale industrial production in the future.

  • 20.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gabrielsson, Erik
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    1,1,2,2-Tetrachloroethane (TeCA) as a Solvent Additive for Organic Hole Transport Materials and Its Application in Highly Efficient Solid-State Dye-Sensitized Solar Cells2015In: Advanced Energy Materials, ISSN 1614-6832, Vol. 5, no 10, article id 1402340Article in journal (Refereed)
    Abstract [en]

    A low-cost, chlorinated hydrocarbon solvent, 1,1,2,2-tetrachloroethane (TeCA), is used as an effective additive for the triarylamine-based organic hole-transport material, Spiro-OMeTAD, which is successfully applied in highly efficient solid-state dye-sensitized solar cells. A record power conversion efficiency of 7.7% is obtained by using the donor (D)-π-acceptor (A)-dye, LEG4, in combination with the new method of TeCA-doping of the hole-transporting material Spiro-OMeTAD.

  • 21.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Huang, Jing
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    AgTFSI as p-Type Dopant for Efficient and Stable Solid-State Dye-Sensitized and Perovskite Solar Cells2014In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 12, p. 3252-3256Article in journal (Refereed)
    Abstract [en]

    A silver-based organic salt, silver bis(trifluoromethane-sulfonyl) imide (AgTFSI), was employed as an effective p-type dopant for the triarylamine-based organic hole-transport material Spiro-MeOTAD, which has been successfully applied in solid-state dye-sensitized solar cells (ssDSCs) and perovskite solar cells (PSCs). The power conversion efficiencies (PCEs) of AgTFSI-doped devices improved by 20%, as compared to the device based on the commonly used oxygen doping both for ssDSCs and PSCs. Moreover, the solid-state dye-sensitized devices exposed to AgTFSI as dopant showed considerably better stability than those of oxygen doped, qualifying this p-type dopant as a promising alterative for the preparation of highly efficient as well as stable ssDSCs and PSCs for the future.

  • 22.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sheibani, Esmaeil
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, Jinbao
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Uppsala University, Sweden.
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT)Dalian, China .
    Carbazole-Based Hole-Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells and Perovskite Solar Cells2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 38, p. 6629-6634Article in journal (Refereed)
    Abstract [en]

    (Graph Presented) Two carbazole-based small molecule hole-transport materials (HTMs) are synthesized and investigated in solid-state dye-sensitized solar cells (ssDSCs) and perovskite solar cells (PSCs). The HTM X51-based devices exhibit high power conversion efficiencies (PCEs) of 6.0% and 9.8% in ssDSCs and PSCs, respectively. These results are superior or comparable to those of 5.5% and 10.2%, respectively, obtained for the analogous cells using the state-of-the-art HTM Spiro-OMeTAD.

  • 23.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Bi, Dongqin
    Gabrielsson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Efficient solid state dye-sensitized solar cells based on an oligomer hole transport material and an organic dye2013In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 46, p. 14467-14470Article in journal (Refereed)
    Abstract [en]

    A low-cost and easily-synthesized organic hole transport material (HTM) X3 bearing triphenylamine units and an organic dye was utilized for solid state dye sensitized solar cells (ssDSCs), which have achieved the power conversion efficiencies of 5.8% and 7.1% under 1 sun and 0.46 sun, respectively, outperforming the ssDSC based on Spiro-OMeTAD 5.4% (1 sun) and 6.4% (0.46 sun).

  • 24.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Uppsala University, Sweden.
    Lin, Lili
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Shandong Normal University, China.
    Qian, Deping
    Chen, Hong
    Zhang, Jinbao
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, Fengling
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Integrated Design of Organic Hole Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells2015In: Advanced Energy Materials, ISSN 1614-6832, Vol. 5, no 3, article id 1401185Article in journal (Refereed)
    Abstract [en]

    A series of triphenylamine-based small molecule organic hole transport materials (HTMs) with low crystallinity and high hole mobility are systematically investigated in solid-state dye-sensitized solar cells (ssDSCs). By using the organic dye LEG4 as a photosensitizer, devices with X3 and X35 as the HTMs exhibit desirable power conversion efficiencies (PCEs) of 5.8% and 5.5%, respectively. These values are slightly higher than the PCE of 5.4% obtained by using the state-of-the-art HTM Spiro-OMeTAD. Meanwhile, transient photovoltage decay measurement is used to gain insight into the complex influences of the HTMs on the performance of devices. The results demonstrate that smaller HTMs induce faster electron recombination in the devices and suggest that the size of a HTM plays a crucial role in device performance, which is reported for the first time.

  • 25.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hu, Jun
    Investigation of Probe Distortion in 28GHz Near-field Antenna Measurement for 5G Communication Application2016In: 2016 PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS), 2016, p. 106-106Conference paper (Refereed)
  • 26.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. University of Washington, United States.
    Zhang, J.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Wang, Linqin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Ruan, C.
    Li, Yuanyuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Boschloo, G.
    Johansson, E. M. J.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, A.
    Jen, A. K. -Y
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tailor-Making Low-Cost Spiro[fluorene-9,9′-xanthene]-Based 3D Oligomers for Perovskite Solar Cells2017In: Chem, ISSN 2451-9308, Vol. 2, no 5, p. 676-687Article in journal (Refereed)
    Abstract [en]

    The power-conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have increased rapidly from about 4% to 22% during the past few years. One of the major challenges for further improvement of the efficiency of PSCs is the lack of sufficiently good hole transport materials (HTMs) to efficiently scavenge the photogenerated holes and aid the transport of the holes to the counter-electrode in the PSCs. In this study, we tailor-made two low-cost spiro[fluorene-9,9′-xanthene] (SFX)-based 3D oligomers, termed X54 and X55, by using a one-pot synthesis approach for PSCs. One of the HTMs, X55, gives a much deeper HOMO level and a higher hole mobility and conductivity than the state-of-the-art HTM, Spiro-OMeTAD. PSC devices based on X55 as the HTM show a very impressive PCE of 20.8% under 100 mW·cm−2 AM1.5G solar illumination, which is much higher than the PCE of the reference devices based on Spiro-OMeTAD (18.8%) and X54 (13.6%) under the same conditions.

  • 27. Yang, Lei
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Bi, Dongqin
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hagfeldt, Anders
    Johansson, Erik M. J.
    Initial Light Soaking Treatment Enables Hole Transport Material to Outperform Spiro-OMeTAD in Solid-State Dye-Sensitized Solar Cells2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 19, p. 7378-7385Article in journal (Refereed)
    Abstract [en]

    Efficient solid state dye-sensitized solar cells (sDSCs) were obtained using a small hole transport material, MeO-TPD (N,N,N',N'-tetrakis(4-methoxyphenyl)benzidine), after an initial light soaking treatment. It was discovered that the light soaking treatment for the MeO-TPD based solar cells is essential in order to achieve the high efficiency (4.9%), which outperforms spiro-OMeTAD based sDSCs using the same dye and device preparation parameters. A mechanism based on Li+ ion migration is suggested to explain the light soaking effect. It was observed that the electron lifetime for the MeO-TPD based sDSC strongly increases after the light soaking treatment, which explains the higher efficiency. After the initial light soaking treatment the device efficiency remains considerably stable with only 0.2% decrease after around 1 month (unsealed cells stored in dark).

  • 28. Zhang, J.
    et al.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Yang, L.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, M. B.
    Vlachopoulos, N.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Boschloo, G.
    Johansson, E. M. J.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, A.
    The Role of 3D Molecular Structural Control in New Hole Transport Materials Outperforming Spiro-OMeTAD in Perovskite Solar Cells2016In: Advanced Energy Materials, ISSN 1614-6832, Vol. 6, no 19, article id 1601062Article in journal (Refereed)
  • 29. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Malin B.
    Hadadian, Mahboubeh
    Baena, Juan Pablo Correa
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Vlachopoulos, Nick
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Constructive Effects of Alkyl Chains: A Strategy to Design Simple and Non-Spiro Hole Transporting Materials for High-Efficiency Mixed-Ion Perovskite Solar Cells2016In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 6, no 13, article id 1502536Article in journal (Refereed)
  • 30. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Malin B.
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Erik M. J.
    Hagfeldt, Anders
    Strategy to Boost the Efficiency of Mixed-Ion Perovskite Solar Cells: Changing Geometry of the Hole Transporting Material2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 7, p. 6816-6825Article in journal (Refereed)
    Abstract [en]

    The hole transporting material (HTM) is an essential component in perovskite solar cells (PSCs) for efficient extraction and collection of the photoinduced charges. Triphenylamine- and carbazole-based derivatives have extensively been explored as alternative and economical HTMs for PSCs. However, the improvement of their power conversion efficiency (PCE), as well as further investigation of the relationship between the chemical structure of the HTMs and the photovoltaic performance, is imperatively needed. In this respect, a simple carbazole-based HTM X25 was designed on the basis of a reference HTM, triphenylamine-based X2, by simply linking two neighboring phenyl groups in a triphenylamine unit through a carbon-carbon single bond. It was found that a lowered highest occupied molecular orbital (HOMO) energy level was obtained for X25 compared to that of X2. Besides, the carbazole moiety in X25 improved the molecular planarity as well as conductivity property in comparison with the triphenylamine unit in X2. Utilizing the HTM X25 in a solar cell with mixed-ion perovskite [HC(NH2)(2)](0.85)(CH3NH3)(0.15)Pb(I0.85Br0.15)(3), a highest reported PCE of 17.4% at 1 sun (18.9% under 0.46 sun) for carbazole-based HTM in PSCs was achieved, in comparison of a PCE of 14.7% for triphenylamine-based HTM X2. From the steady-state photoluminescence and transient photocurrent/photovoltage measurements, we conclude that (1) the lowered HOMO level for X25 compared to X2 favored a higher open-circuit voltage (V-oc) in PSCs; (2) a more uniform formation of X25 capping layer than X2 on the surface of perovskite resulted in more efficient hole transport and charge extraction in the devices. In addition, the long-term stability of PSCs with X25 is significantly enhanced compared to X2 due to its good uniformity of HTM layer and thus complete coverage on the perovskite. The results provide important information to further develop simple and efficient small molecular HTMs applied in solar cells.

  • 31. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
    Yang, Li
    Ruan, Changqing
    Wang, Linqin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Zhang, Wei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Vlachopoulos, Nick
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian, China.
    Hagfeldt, Anders
    Johansson, Erik M. J.
    The Importance of Pendant Groups on Triphenylamine-Based Hole Transport Materials for Obtaining Perovskite Solar Cells with over 20% Efficiency2018In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 8, no 2, article id 1701209Article in journal (Refereed)
    Abstract [en]

    Tremendous progress has recently been achieved in the field of perovskite solar cells (PSCs) as evidenced by impressive power conversion efficiencies (PCEs); but the high PCEs of >20% in PSCs has so far been mostly achieved by using the hole transport material (HTM) spiro-OMeTAD; however, the relatively low conductivity and high cost of spiro-OMeTAD significantly limit its potential use in large-scale applications. In this work, two new organic molecules with spiro[fluorene-9,9-xanthene] (SFX)-based pendant groups, X26 and X36, have been developed as HTMs. Both X26 and X36 present facile syntheses with high yields. It is found that the introduced SFX pendant groups in triphenylamine-based molecules show significant influence on the conductivity, energy levels, and thin-film surface morphology. The use of X26 as HTM in PSCs yields a remarkable PCE of 20.2%. In addition, the X26-based devices show impressive stability maintaining a high PCE of 18.8% after 5 months of aging in controlled (20%) humidity in the dark. We believe that X26 with high device PCEs of >20% and simple synthesis show a great promise for future application in PSCs, and that it represents a useful design platform for designing new charge transport materials for optoelectronic applications.

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