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Strategies for Performance Improvement of Quantum Dot Sensitized Solar Cells
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0001-6005-2302
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantum dot sensitized solar cells (QDSCs) constitute one of the most promising low-cost solutions that are explored for the world’s needs of clean and renewable energy. Efficient, low-toxic and stable QDSCs for large-scale applications have formed the subject for the solar cell research during recent years. This circumstance also forms the motivation for this thesis, where the results of my studies to improve the efficiency and stability of green QDSCs are presented and discussed.

The surface condition of quantum dots (QDs) is always crucial to the performance of QDSCs, since surface ligands can influence the loading amount of QDs, and that the surface defects can induce charge recombination in the solar cells. In this thesis work, a hybrid passivation approach was firstly utilized to improve the photovoltaic performance of CdSe QDs. After hybrid passivation by MPA and iodide ions, the loading efficiency of the QDs was increased with the ligands of MPA, and the surface defects on the QDs were reduced by the iodide ions, both contributing to an enhancement in the efficiency of the CdSe based QDSCs. This hybrid passivation strategy was then employed for low-toxic CuInS2 QDs, and was also demonstrated as an effective way to modify the surface state of the CuInS2 QDs and improve the performance of the QDSCs based on CuInS2 QDs.  

To improve the stability of the QDSCs, solid state quantum dot sensitized solar cells (ss-QDSCs) based on CuInS2 QDs were investigated. In addition to the hybrid passivation, increasing the pore size of the TiO2 active layer and changing the composition of the CuInS2 QDs were also found to be useful approaches to improve the performance of the ss-QDSCs based on CuInS2 QDs. Furthermore, for the most used hole transport material- Spiro-OMeTAD- in solid state solar cells, silver bis(trifluoromethanesulfonyl)imide was shown to be an effective p-type dopant to increase its conductivity and to improve the performance of the solar cells based on it.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 71 p.
Series
TRITA-BIO-Report, ISSN 1654-2312 ; 2016:11
Keyword [en]
quantum dot sensitized solar cells
National Category
Chemical Engineering
Research subject
Theoretical Chemistry and Biology
Identifiers
URN: urn:nbn:se:kth:diva-186363ISBN: 978-91-7595-995-5 (print)OAI: oai:DiVA.org:kth-186363DiVA: diva2:927037
Public defence
2016-06-07, FB 42, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Supervisors
Note

QC 20160516

Available from: 2016-05-16 Created: 2016-05-10 Last updated: 2016-05-16Bibliographically approved
List of papers
1. Improved Performance of Colloidal CdSe Quantum Dot-Sensitized Solar Cells by Hybrid Passivation
Open this publication in new window or tab >>Improved Performance of Colloidal CdSe Quantum Dot-Sensitized Solar Cells by Hybrid Passivation
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2014 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 21, 18808-18815 p.Article in journal (Refereed) Published
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.

Keyword
quantum dot-sensitized solar cells, colloidal quantum dots, hybrid passivation, solution process
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-158822 (URN)10.1021/am504536a (DOI)000344978200057 ()2-s2.0-84910117109 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation
Note

QC 20150127

Available from: 2015-01-27 Created: 2015-01-12 Last updated: 2017-12-05Bibliographically approved
2. Photovoltaic Performance Improvement Strategies for Colloidal CuInS2 QDs: Hybrid Passivation vs ZnS shell
Open this publication in new window or tab >>Photovoltaic Performance Improvement Strategies for Colloidal CuInS2 QDs: Hybrid Passivation vs ZnS shell
(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-186357 (URN)
Note

QS 201605

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2016-05-16Bibliographically approved
3. Efficiency Enhancement of Solid-State Quantum Dot-Sensitized Solar Cells by Quality Optimizing of Colloidal CuInS2 Quantum Dots
Open this publication in new window or tab >>Efficiency Enhancement of Solid-State Quantum Dot-Sensitized Solar Cells by Quality Optimizing of Colloidal CuInS2 Quantum Dots
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-186360 (URN)
Note

QC 20160518

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2016-05-18Bibliographically approved
4. AgTFSI as p-Type Dopant for Efficient and Stable Solid-State Dye-Sensitized and Perovskite Solar Cells
Open this publication in new window or tab >>AgTFSI as p-Type Dopant for Efficient and Stable Solid-State Dye-Sensitized and Perovskite Solar Cells
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2014 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 12, 3252-3256 p.Article in journal (Refereed) Published
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.

Keyword
doping, dyes/pigments, perovskites, silver, solar cells
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-158440 (URN)10.1002/cssc.201402678 (DOI)000345976200006 ()25257308 (PubMedID)2-s2.0-84918784521 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation
Note

QC 20150108

Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2017-12-05Bibliographically approved

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