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  • 1. He, Wang
    et al.
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Gustafsson, Mats
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    RF Compliance Study of Temperature Elevation in Human Head Model Around 28 GHz for 5G User Equipment Application: Simulation Analysis2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6Article in journal (Refereed)
    Abstract [en]

    The crowdedness of current cellular bands and the demand for higher transmission speed prompt the use of the millimeter-wave spectrum for the next-generation mobile communication. In the millimeter-wave frequencies, the dosimetric quantity for human exposure to electromagnetic fields changes from the specific absorption rate to incident power density. In this paper, we used 28-GHz beam-steering patch arrays, a dipole antenna, and plane waves to investigate the temperature elevation in a multi-layer model of human head and its correlation with power density metrics. The power density averaged over one square-centimeter in free space and the peak temperature elevation in tissue at 28 GHz have good correlation. The peak temperature elevation indicated by the power density averaged one square-centimeter also agrees well with the peak temperature elevation induced by the plane waves. The results show that the averaging area of a few square-centimeters may be a good candidate for the spatial-average power density. The findings provide valuable input to the ongoing revision and updating of relevant safety standards and guidelines.

  • 2.
    He, Wang
    et al.
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Elect Res, Hangzhou 310058, Peoples R China..
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Ericsson Res, Ericsson AB, SE-16480 Stockholm, Sweden..
    Scialacqua, Lucia
    Microwave Vis Grp, I-00071 Pomezia, Italy..
    Ying, Zhinong
    Sony Corp, Sony Res Ctr, SE-22188 Lund, Sweden.;Aalborg Univ, Propagat & Mm Wave Sect APMS, Dept Elect Syst, DK-9220 Aalborg, Denmark..
    Scannavini, Alessandro
    Microwave Vis Grp, I-00071 Pomezia, Italy..
    Foged, Lars Jacob
    Microwave Vis Grp, I-00071 Pomezia, Italy..
    Zhao, Kun
    Sony Corp, Sony Res Ctr, SE-22188 Lund, Sweden.;Aalborg Univ, Propagat & Mm Wave Sect APMS, Dept Elect Syst, DK-9220 Aalborg, Denmark..
    Di Paola, Carla
    Aalborg Univ, Propagat & Mm Wave Sect APMS, Dept Elect Syst, DK-9220 Aalborg, Denmark..
    Zhang, Shuai
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Elect Res, Hangzhou 310058, Peoples R China..
    Fast Power Density Assessment of 5G Mobile Handset Using Equivalent Currents Method2021In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 69, no 10, p. 6857-6869Article in journal (Refereed)
    Abstract [en]

    As the fifth-generation (5G) mobile communication is utilizing millimeter-wave (mmWave) frequency bands, electromagnetic field (EMF) exposure emitted from a 5G mmWave mobile handset should be evaluated and compliant with the relevant EMF exposure limits in terms of peak spatial-average incident power density (PD). In this work, a fast PD assessment method for a 5G mmWave mobile handset using the equivalent current (EQC) method is proposed. The EQC method utilizes the intermediate-field (IF) data collected by a spherical measurement system to reconstruct the EQCs over a reconstruction surface and then computes the PD in close proximity of the mobile handset with acceptable accuracy. The performance of the proposed method is evaluated using a mmWave mobile handset mock-up equipped with four quasi-Yagi antennas. The assessed PD results are compared with those computed using full-wave simulations and also those measured with a planar near-field (NF) scanning system. In addition, three influencing factors related to the accuracy of the EQC method, namely, the angular resolution, the phase error, and the handset position in the IF measurements, are also analyzed. The proposed method is a good candidate for fast PD assessment of EMF exposure compliance testing in the mmWave frequency range.

  • 3.
    He, Wang
    et al.
    Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Peoples R China..
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Ericsson AB, Ericsson Res, S-16480 Stockholm, Sweden.;KTH Royal Inst Technol, Dept Electromagnet Engn, S-10044 Stockholm, Sweden..
    Yao, Yuanqing
    Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Peoples R China..
    Colombi, Davide
    Ericsson AB, Ericsson Res, S-16480 Stockholm, Sweden..
    Ying, Zhinong
    Sony Corp, Sony Res Ctr, S-22188 Lund, Sweden..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Optical Network Laboratory (ON Lab). Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Peoples R China.;KTH Royal Inst Technol, Dept Electromagnet Engn, S-10044 Stockholm, Sweden..
    Implications of Incident Power Density Limits on Power and EIRP Levels of 5G Millimeter-Wave User Equipment2020In: IEEE Access, E-ISSN 2169-3536, Vol. 8, p. 148214-148225Article in journal (Refereed)
    Abstract [en]

    User equipment (UE) is required to comply with the relevant radio frequency (RF) electromagnetic field (EMF) exposure limits, which are of relevance to establish the maximum permissible transmitted power and the maximum equivalent isotropically radiated power (EIRP). Recently, international RF EMF exposure guidelines, such as those published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) as well as by the IEEE, have been updated. In this paper, the implications of the revised incident power density limits are investigated in terms of maximum permissible transmitted power and the maximum EIRP for devices operating in close proximity of the user. A similar analysis is conducted according to the US Federal Communications Commission (FCC) regulation on RF exposure. EMF compliance of UE is studied by means of numerical modelling of patch antenna arrays of different array sizes taking into consideration of possible beam-steering operations, at frequencies ranging from 10 GHz to 100 GHz. The results are compared with the 3rd Generation Partnership Project (3GPP) requirements on the total radiated power (TRP) and EIRP levels. The present implications of the incident power density limits for 5G millimeter-wave UE will give valuable insights to mobile equipment manufacturers, network operators, and standardization bodies.

  • 4. Huang, Jing
    et al.
    Zhou, Jingjian
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Haraldsson, Klas Tommy
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Clemments, Alden
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Fujii, Minoru
    Department of Electrical and Electronic Engineering, Kobe University, Rokkodai, Nada, Kobe, 657-8501 Japan.
    Sugimoto, Hiroshi
    Department of Electrical and Electronic Engineering, Kobe University, Rokkodai, Nada, Kobe, 657-8501 Japan.
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Sychugov, Ilya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Triplex Glass Laminates with Silicon Quantum Dots for Luminescent Solar Concentrators2020In: Solar RRL, E-ISSN 2367-198X, Vol. 4, no 9, article id 2000195Article in journal (Refereed)
    Abstract [en]

    Luminescent solar concentrator (LSC) is a promising technology to integrate semitransparent photovoltaic (PV) systems into modern buildings and vehicles. Silicon quantum dots (QDs) are good candidates as fluorophores in LSCs, due to the absence of overlap between absorption and emission spectra, high photoluminescence quantum yield (PLQY), good stability, nontoxicity, and element abundance. Herein, LSCs based on Si QDs/polymer nanocomposites are fabricated in a triplex glass configuration. A special polymer matrix (off-stoichiometric thiol-ene, OSTE) is used, which improves Si nanocrystal quantum yield. Herein, a comprehensive investigation to improve the performance of LSCs by exploring different strategies under the guidance of a theoretical description is conducted. Among these strategies, the systematical enhancement of PLQY of the nanocomposite is achieved by tuning the thiol/allyl group ratio in the OSTE matrix. In addition, ligand selection and loading optimization for QDs reduce the total scattering loss in the device. Finally, an optical power efficiency of 7.9% is achieved for an optimized LSC prototype (9 x 9 x 0.6 cm(3), transmittance approximate to 62% at 500 nm) based on Si QDs/OSTE nanocomposite, which shows good potential of this material system in LSC fabrication.

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  • 5. Li, Xing
    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.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hu, Yue
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hua, Jianli
    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.
    Tian, He
    Molecular engineering of D-A-pi-A sensitizers for highly efficient solid-state dye-sensitized solar cells2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 7, p. 3157-3166Article in journal (Refereed)
    Abstract [en]

    Two newquinoxaline-based D-A-pi-A organic sensitizers AQ309 and AQ310 have been designed and synthesized employing 3,4-ethylenedioxythiophene (EDOT) and cyclopentadithiophene (CPDT) as plinker units, respectively. The new AQ309 and AQ310 dyes have been applied in all-solid-state dye-sensitized solar cells (ssDSSCs). An impressive record photoelectric conversion efficiency (PCE) of 8.0% for AQ310-based ssDSSCs using Spiro-OMeTAD as the hole transport material (HTM) was obtained under standard AM 1.5 (100 mW cm (2)) solar intensity. This clearly outperforms the PCE of the state-of-theart organic D-pi-A dye LEG4-based devices showing a PCE of 7.3% under the same conditions. Moreover, an excellent high PCE of 8.6% was also recorded for AQ310-based devices under 50% solar intensity. Meanwhile, the AQ310-based ssDSSCs showed a much longer electron lifetime according to the transient photovoltage decay measurement, demonstrating lower charge recombination losses in the devices. Photo-induced absorption spectroscopy (PIA) indicated that AQ310 could be more efficiently regenerated by Spiro-OMeTAD. These results show that molecular engineering is a promising strategy to develop D-A-pi-A organic sensitizers for highly efficient ssDSSCs.

  • 6.
    Li, Yuanyuan
    et al.
    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.
    Cheng, Ming
    Jungstedt, Erik
    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.
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Berglund, Lars
    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.
    Optically Transparent Wood Substrate for Perovskite Solar Cells2019In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 7, no 6, p. 6061-6067Article in journal (Refereed)
    Abstract [en]

    Transparent wood is a candidate for use as an energy-saving building material due to its low density (ca. 1.2 g/cm(3)), high optical transmittance (over 85% at 1 mm thickness), low thermal conductivity (0.23 W m(-1) K-1), and good load-bearing performance with tough failure behavior (no shattering). High optical transmittance also makes transparent wood a candidate for optoelectronic devices. In this work, for the first time, perovskite solar cells processed at low temperature (<150 degrees C) were successfully assembled directly on transparent wood substrates. A power conversion efficiency up to 16.8% was obtained. The technologies demonstrated may pave the way for integration of solar cells with light transmitting wood building structures for energy-saving purposes.

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  • 7.
    Liu, Peng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Wang, Linqin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), 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), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Hao, Yan
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. 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). KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Boschloo, Gerrit
    Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden..
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Molecular Engineering of D-pi-A Type of Blue-Colored Dyes for Highly Efficient Solid-State Dye-Sensitized Solar Cells through Co-Sensitization2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 42, p. 35946-35952Article in journal (Refereed)
    Abstract [en]

    A novel blue-colored organic donor-pi-acceptor sensitizer, the so-called MKA16 dye, has been employed to construct solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2',7-,7'-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9'-spirobifuorene (Spiro-OMeTAD) as hole-transport material, a good conversion efficiency of 5.8% was recorded for cells based on the MKA16 dye and a high photovoltage of 840 mV in comparison with 5.6% efficiency using the known (Dyenamo Blue) dye. By co-sensitization using the orange-colored D35 dye and MKA16 together, the solid-state solar cells showed an excellent efficiency of 7.5%, with a high photocurrent of 12.41 mA cm(-2) and open-circuit voltage of 850 mV. The results show that the photocurrent of ssDSSCs can be significantly improved by co-sensitization mainly attributed to the wider light absorption range contributing to the photocurrent. In addition, results from photo-induced absorption spectroscopy show that the dye regeneration is efficient in co-sensitized solar cells. The current results possible routes of improving the design of aesthetic and highly efficient ssDSSCs.

  • 8.
    Liu, Tianqi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Li, Ge
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Shen, Nannan
    State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123.
    Wang, Linqin
    Center of Artificial Photosynthesis for Solar Fuels, School of Science, Westlake University, Hangzhou 310024.
    Timmer, Brian
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Zhou, Shengyang
    Nanotechnology and Functional Materials, Department of Materials Sciences and Engineering, The Ångström Laboratory, Uppsala University, Uppsala 75103.
    Zhang, Biaobiao
    Center of Artificial Photosynthesis for Solar Fuels, School of Science, Westlake University, Hangzhou 310024.
    Kravchenko, Alexander
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ahlquist, Mårten S. G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts2022In: CCS Chemistry, ISSN 2096-5745, Vol. 4, no 7, p. 2481-2490Article in journal (Refereed)
    Abstract [en]

    Isolation of RuIII-bda (17-electron specie) complex with an aqua ligand (2-electron donor) is challenging due to violation of the 18-electron rule. Although considerable efforts have been dedicated to mechanistic studies of water oxidation by the Ru-bda family, the structure and initial formation of the RuIII-bda aqua complex are still controversial. Herein, we challenge this often overlooked step by designing a pocket-shape Ru-based complex 1. The computational studies showed that 1 possesses the crucial hydrophobicity at the RuV(O) state as well as similar probability of access of terminal O to solvent water molecules when compared with classic Ru-bda catalysts. Through characterization of single-crystal structures at the RuII and RuIII states, a pseudo seven-coordinate “ready-to-go” aqua ligand with RuIII...O distance of 3.62 Å was observed. This aqua ligand was also found to be part of a formed hydrogen-bonding network, providing a good indication of how the RuIII-OH2 complex is formed.

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  • 9.
    Lundgren, Johan
    et al.
    Lund Univ, Dept Elect & Informat Technol, Lund, Sweden..
    Helander, Jakob
    Lund Univ, Dept Elect & Informat Technol, Lund, Sweden..
    Gustafsson, Mats
    Lund Univ, Dept Elect & Informat Technol, Lund, Sweden..
    Sjoberg, Daniel
    Lund Univ, Dept Elect & Informat Technol, Lund, Sweden.;Lund Univ, Electromagnet Theory, Lund, Sweden..
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Ericsson AB, Ericsson Res, Stockholm, Sweden..
    Colombi, Davide
    Ericsson Res, Stockholm, Sweden..
    A Near-Field Measurement and Calibration Technique: Radio-Frequency Electromagnetic Field Exposure Assessment of Millimeter-Wave 5G Devices2021In: IEEE Antennas & Propagation Magazine, ISSN 1045-9243, E-ISSN 1558-4143, Vol. 63, no 3, p. 77-88Article in journal (Refereed)
    Abstract [en]

    Accurate and efficient measurement techniques are needed for an exposure assessment of 5G portable devices, which are expected to utilize frequencies beyond 6 GHz with respect to radio-frequency (RF) electromagnetic field (EMF) exposure limits. At above 6 GHz, these limits are expressed in terms of the incident power density, thus requiring the EMFs to be evaluated with high precision in close vicinity to the device under test (DUT), i.e., in the near-field region of the radiating antenna. This article presents a cutting-edge near-field measurement technique suited for these needs. The technique, based on source reconstruction on a predefined surface representing the radiating aperture of the antenna, requires two sets of measurements: one of the DUT and one of a small aperture. This second measurement functions as a calibration of both the measurement probe impact on the received signal and the experimental setup in terms of the relative distance between the probe and the DUT. Results are presented for a 28- and a 60-GHz antenna array, both of which were developed for 5G applications. The computed power density is compared with simulations at evaluation planes residing as close as one fifth of a wavelength (lambda/5) away from the DUT.

  • 10.
    Ou, Yangmei
    et al.
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Sun, Anxin
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Li, Haibei
    Shandong Univ, Sch Ocean, Weihai 264209, Peoples R China..
    Wu, Tai
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Zhang, Dongyang
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Xu, Peng
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Zhao, Rongmei
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Zhu, Liqiong
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Wang, Runtao
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Hua, Yong
    Yunnan Univ, Yunnan Key Lab Micro Nano Mat & Technol, Sch Mat & Energy, Kunming 650091, Yunnan, Peoples R China..
    Ding, Liming
    Natl Ctr Nanosci & Technol, Ctr Excellence Nanosci CAS, Key Lab Nanosyst & Hierarch Fabricat CAS, Beijing 100190, Peoples R China..
    Developing D-pi-D hole-transport materials for perovskite solar cells: the effect of the pi-bridge on device performance2021In: Materials Chemistry Frontiers, E-ISSN 2052-1537, Vol. 5, no 2, p. 876-884Article in journal (Refereed)
    Abstract [en]

    Three cost-effective D-pi-D hole transport materials (HTMs) with different pi-bridges, including biphenyl (SY1), phenanthrene (SY2), and pyrene (SY3), have been synthesized via a one-pot reaction with cheap commercially available starting materials for application in organic-inorganic hybrid perovskite solar cells (PSCs). The effects of the various pi-bridges on the photophysical, electrochemical, and electrical properties, and film morphologies of the materials, as well as on the photovoltaic properties of the PSCs, have been systematically investigated accordingly. Our results clearly show that HTM-SY3 with pyrene as the pi-bridge exhibits higher hole mobility and better hole extraction/transport and film formation abilities than the other two HTMs. Devices that employed SY3 as the HTM show impressive power conversion efficiency (PCE) values of 19.08% and 13.41% in (FAPbI(3))(0.85)(MAPbBr(3))(0.15)- and CsPbI2Br-based PSCs, respectively, which are higher than those of the reference HTM-SY1- and SY2-based ones. Our studies demonstrate a promising strategy to rationally design and synthesize low-cost and efficient HTMs through structural engineering for use in PSCs.

  • 11.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fischer, Andreas C.
    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. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Erratum to: Structure and function relationships in alkylammonium lead(II) iodide solar cells2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 17, p. 9317-9317Article in journal (Refereed)
  • 12. Scialacqua, L.
    et al.
    Foged, L. J.
    Scannavini, A.
    Herbiniere, F.
    Mioc, F.
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ying, Z.
    Bolin, T.
    Advanced measurement post-processing by equivalent currents on small 5G antennas2018In: 12th European Conference on Antennas and Propagation (EuCAP 2018), Institution of Engineering and Technology, 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    Fifth-Generation (5G) mobile communication demands a wide use of multi beam scanning array antennas, providing effective coverage performances at millimeter waves [1-3]. In particular, when the telecommunication channel is characterized by a reduced signal to noise ratio, an omni like radiation pattern could be generated by the beam scanning antenna system. The testing of the AUT (Antenna Under Test), in such conditions, is typically performed with low directive reference antennas. These antennas can suffer of the interaction with the feeding cable. The measurement post-processing by the equivalent currents approach (EQC) [4-7], implemented in the MVG software INSIGHT [8], can be used for diagnostic investigations on this kind of reference antennas and to filter undesired currents on the feeding cable. In this paper the EQC approach is applied, for the first time, on diagnostic and filtering of feeding cable on a measurement of a low directive antenna for 5G tests.

  • 13. Shen, Z.
    et al.
    Xu, Bo
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hu, Y.
    Yu, Y.
    Ding, H.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hua, J.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. Dalian University of Technology (DUT), Dalian, China.
    Tian, H.
    High performance solid-state dye-sensitized solar cells based on organic blue-colored dyes2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 3, p. 1242-1247Article in journal (Refereed)
    Abstract [en]

    The development of novel photosensitizers with very high molar extinction coefficients and broad absorption spectra to enhance the light harvesting efficiency providing high PCEs for solid state dye sensitized solar cells (sDSCs) is a main target for improvement. In this work, two novel organic blue-colored dyes termed S4 and S5 with indeno[1,2-b]thiophene functionalized triphenylamine as the donor, 2,3-diphenylpyrido[3,4-b]pyrazine (PP) or 2,3-diphenylquinoxaline (QT) as the auxiliary acceptor and cyclopentadithiophene (CPDT) as the π-linker were designed and synthesized for sDSCs. S5 containing the QT unit as the electron-withdrawing group exhibits a high molar extinction coefficient of 6.3 × 104 M-1 cm-1 at 600 nm. Most importantly, the S5-based sDSCs shows record PCEs of 7.81% and 8.25% under one sun and 0.5 sun light intensities, respectively, exceeding the PCE of LEG4-based solar cells (7.34%). To the best of our knowledge, this is the first case where an organic blue-colored dye displays a PCE over 7.8% in sDSCs, thus representing record efficiencies for sDSCs. These results clearly show that molecular engineering is a viable way to develop blue-colored dyes with high molar extinction coefficients for use in highly efficient sDSCs. Also, blue-colored dyes open up co-sensitization strategies in combination with traditional organic dyes with yellow-red colours.

  • 14.
    Wang, Linqin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, Fuguo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Tianqi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, Wei
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Cai, Bin
    He, Lanlan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Guo, Yu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Yang, Xichuan
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    A crosslinked polymer as dopant-free hole-transport material for efficient n-i-p type perovskite solar cells2021In: Journal of Energy Chemistry, ISSN 2095-4956, E-ISSN 2096-885X, Vol. 55, p. 211-218Article in journal (Refereed)
    Abstract [en]

    A new crosslinked polymer, called P65, with appropriate photo-electrochemical, opto-electronic, and thermal properties, has been designed and synthesized as an efficient, dopant-free, hole-transport material (HTM) for n-i-p type planar perovskite solar cells (PSCs). P65 is obtained from a low-cost and easily synthesized spiro[fluorene-9,9′-xanthene]-3′,6′-diol (SFX-OH)-based monomer X65 through a free-radical polymerization reaction. The combination of a three-dimensional (3D) SFX core unit, hole-transport methoxydiphenylamine group, and crosslinked polyvinyl network provides P65 with good solubility and excellent film-forming properties. By employing P65 as a dopant-free hole-transport layer in conventional n-i-p type PSCs, a power conversion efficiency (PCE) of up to 17.7% is achieved. To the best of our knowledge, this is the first time a 3D, crosslinked, polymeric dopant-free HTM has been reported for use in conventional n-i-p type PSCs. This study provides a new strategy for the future development of a 3D crosslinked polymeric dopant-free HTM with a simple synthetic route and low-cost for commercial, large-scale applications in future PSCs.

  • 15.
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    EMF Exposure and Radiation Performance of Millimeter-Wave Antennas in 5G Mobile Terminals2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since 2019, 5G has been rolled out in many countries. To support the demand of increasing traffic capacity, for the first time, the millimeter-wave (mmWave) frequency spectrum is exploited for the mobile wireless telecommunication technologies. For the telecommunication industry,  many questions are raised with the advent of 5G mmWave, including what would impact the performance of mmWave antennas in a mobile terminal and how to evaluate the impacts/effects. This thesis focuses on two topics about 5G mmWave mobile antenna performance. One is the radiation performance for mmWave antennas integrated in the mobile terminal. The other is electromagnetic field (EMF) exposure from mmWave mobile antennas. 

    When integrated into a mobile terminal, the radiation performance of mmWave antennas can be affected by the housing conditions, for example, phone casing and display, etc. By detailed step-by-step simulation analyses, different types of housing effects, as well as the effects of the user's hand, are investigated. The effects of realistic housing conditions are also examined with far-field measurements and near-field antenna diagnose based on the solution to the inverse problem. The analyses provide useful insights into mmWave mobile antenna design and measurements in realistic housing environments. 

    The mobile terminal needs to comply with regulations on EMF exposure before putting them on the market. By carrying out multi-physics simulation hybridizing the electromagnetic problem and the thermal problem, the correlation between tissue temperature rise and incident power density generated by the mmWave antennas is studied. Various field combination methods for EMF exposure from array antenna elements are investigated with simulations and measurements, and methods for calculating the upper bound of EMF exposure from the mmWave antenna array are developed. 

    Recently, the international EMF exposure guidelines have been revised, including the changes of the EMF exposure limits in the mmWave frequencies. The implications of the revised limits are investigated by assessing the maximum power and maximum equivalent isotropically radiated power (EIRP) that are allowed to be transmitted from mmWave mobile antennas in the ideal as well as realistic scenarios. The obtained results provide valuable input to the device manufacturer, network operators, and standardization bodies.

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  • 16.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Gustafsson, Mats
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, Lund, Sweden..
    Shi, Shuai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ying, Zhinong
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, Lund, Sweden..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Upper Bound Study of 5G RF EMF Exposure2018In: 2018 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING, IEEE , 2018, p. 397-398Conference paper (Refereed)
    Abstract [en]

    Power density emitted by 5G user equipment should not exceed the power density limits set by compliance guidelines. When the amplitude of each port of millimeter-wave array antennas is uniform, the power density maximization problem can be relaxed to a semi-definite program. In this paper, the effect of sampling widths is considered for the maximum power density calculation. The results show that when the sampling distance is less than a half wavelength, the sampling rate should be higher than the Nyquist rate.

  • 17.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Gustafsson, Mats
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    Shi, Shuai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Zhao, Kun
    Sony Mobile Commun AB, Res & Technol, Network Technol Lab, SE-22188 Lund, Sweden..
    Ying, Zhinong
    Sony Mobile Commun AB, Res & Technol, Network Technol Lab, SE-22188 Lund, Sweden..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Radio Frequency Exposure Compliance of Multiple Antennas for Cellular Equipment Based on Semidefinite Relaxation2019In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 61, no 2, p. 327-336Article in journal (Refereed)
    Abstract [en]

    Human exposure to radio frequency (RF) electromagnetic fields should not exceed the exposure limits set by the relevant regulatory guidelines. In this paper, we provide approaches to determine upper bounds of maximum exposure from multiple antennas. When the total transmitted power is fixed, the maximum exposure can be determined by an eigenvalue decomposition. If an individual antenna has additional power constraint, the exposure maximization problem can be relaxed to a semidefinite program. Two case studies are given to demonstrate the approaches to the maximum exposure of cellular equipment using multiple antennas. The methods and the obtained results provide valuable insights into RF compliance procedures of cellular equipment.

  • 18.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Helander, Jakob
    Ericsson, Andreas
    Ying, Zhinong
    He, Sailing
    Gustafsson, Mats
    Sjoberg, Daniel
    Investigation of Planar Near-Field Measurement of Millimeter-Wave Antenna for 5G Application2016In: 2016 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP), IEEE , 2016, p. 600-601Conference paper (Refereed)
    Abstract [en]

    The requirement of higher data rates and the emergence of new wireless device demands in future 5G communication put millimeter-wave frequencies in focus. To investigate electromagnetic-filed exposure at such frequencies for 5G cellular phone application, a planar near-field antenna measurement system is established. A tapered open-ended rectangular waveguide was used as the probe antenna, and a patch array antenna operating at 28 GHz was used as antenna under test. The distribution of power density above the antenna surface was calculated based on the measured data and the plane wave expansion method.

  • 19.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Scialacqua, L.
    Scannavini, A.
    Foged, L. J.
    Ying, Z.
    Bolin, T.
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Antenna diagnosis and power density calculation of 5G millimeter-wave mobile terminal using inverse source technique2018In: 12th European Conference on Antennas and Propagation (EuCAP 2018), Institution of Engineering and Technology, 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    Millimeter-wave antennas may suffer from stronger effects of surface waves in 5G mobile terminals. In this paper, printed 28 GHz antennas are implemented in a mobile handset mock-up. The influence of surface waves is examined by the reconstructed equivalent currents obtained through the inverse source technique. The obtained equivalent currents are reused for the power density calculation for the purpose of millimeter-wave exposure assessment. The results provide valuable insight into 5G millimeter-wave mobile antenna design and measurement.

  • 20.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ying, Z.
    Gustafsson, M.
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Effective beam-scanning efficiency of millimeter-wave subarrays for 5G user equipment application2018In: IET Conference Publications, Institution of Engineering and Technology , 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    The forthcoming 5G communication system is expected to adopt millimeter-wave bands in order to satisfy the ever-growing traffic explosion. The coverage efficiency was proposed in earlier works to evaluate the beam-scanning capability and coverage performance of array antennas implemented in 5G user equipment. However, when multi-subarray configurations are introduced into user equipment, the coverage efficiency fails to reflect the coverage performance of each subarray under the influence of housing. In this paper, we use the effective beam-scanning efficiency to evaluate the coverage performance of a subarray covered by a superstrate. The results provide valuable insight into 5G mobile antenna design.

  • 21.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Ericsson AB, Ericsson Res, SE-16480 Stockholm, Sweden..
    Ying, Zhinong
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, SE-22188 Lund, Sweden..
    Scialacqua, Lucia
    Microwave Vis Italy, I-00040 Pomezia, Italy..
    Scannavini, Alessandro
    Microwave Vis Italy, I-00040 Pomezia, Italy..
    Foged, Lars Jacob
    Microwave Vis Italy, I-00040 Pomezia, Italy..
    Bolin, Thomas
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, SE-22188 Lund, Sweden..
    Zhao, Kun
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, SE-22188 Lund, Sweden.;Aalborg Univ, Dept Elect Syst, Antennas Propagat & Radio Networking Sect, DK-9220 Aalborg, Denmark..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China.
    Gustafsson, Mats
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    Radiation Performance Analysis of 28 GHz Antennas Integrated in 5G Mobile Terminal Housing2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 48088-48101Article in journal (Refereed)
    Abstract [en]

    Radiation from printed millimeter-wave antennas integrated in mobile terminals is affected by surface currents on chassis, guided waves trapped in dielectric layers, superstrates, and the user's hand, making mobile antenna design for 5G communication challenging. In this paper, four canonical types of printed 28-GHz antenna elements are integrated in a 5G mobile terminal mock-up. Different kinds of terminal housing effects are examined separately, and the terminal housing effects are also diagnosed through equivalent currents by using the inverse source technique. To account for the terminal housing effects on a beam-scanning antenna subarray, we propose the effective beam-scanning efficiency to evaluate its coverage performance. This paper presents the detailed analysis, results, and new concepts regarding the terminal housing effects, and thereby provides valuable insight into the practical 5G mobile antenna design and radiation performance characterization.

  • 22.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    RF EMF Exposure of Beam-Steering Slot Array in 5G User Equipment at 15 GHz2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 177-178Conference paper (Refereed)
    Abstract [en]

    Above 6 GHz or 10 GHz, the radio frequency (RF) electro-magnetic field (EMF) exposure of user equipment (UE) is evaluated in terms of free space power density. The RF EMF exposure compliance of the fifth-generation (5G) UE with an 8 x 1 beam-steering slot array is analyzed in this paper. The maximum exposure (ME) and corresponding maximum permissible radiated power (MPRP) are calculated for different regulatory guidelines. The results give a good estimation on the range of compliance distance and MPRP of 5G UE, and provide the insight for the future RF EMF exposure compliance for the 5G communication. More results and comparisons of different sorts of arrays will be presented in the conference.

  • 23.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Understandings of Maximum Spatially-Averaged Power Density in 5G RF EMF Exposure Study2017In: 2017 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY: SMALL ANTENNAS, INNOVATIVE STRUCTURES, AND APPLICATIONS (IWAT), IEEE , 2017, p. 115-117Conference paper (Refereed)
    Abstract [en]

    In the millimeter-wave (mmW) frequency band, radio frequency electromagnetic field (RF EMF) exposure is evaluated in terms of free space power density rather than the localized specific absorption rate (SAR) used in current cellular communications. In this study, we investigated RF EMF exposure of user equipment (UE) mock-ups employing a patch array operating at 15 GHz. Different understandings of maximum spatially-averaged power density to comply with different regulatory requirements are studied. Based on free space power density, the maximum permissible transmitted power (MPTP) of UE is calculated to compare the influence of different understandings. The analysis and results suggest that there is 1-2.6 dB MPTP difference for the ICNIRP limits and 0.1-1 dB MPTP difference for the proposed FCC limits depending on the varying compliance distance.

  • 24.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Thors, Björn
    Colombi, Davide
    Lundberg, Oscar
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Power Density Measurements at 15 GHz for RF EMF Compliance Assessments of 5G User Equipment2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6584-6595Article in journal (Refereed)
    Abstract [en]

    In this paper, different measurement schemes are studied in order to investigate the possibilities and limitations of scalar-and vector-based measurement systems for radio frequency electromagnetic fields compliance assessments of fifth generation mobile communication user equipment (UE). Two UE antenna array designs, transmitting at 15 GHz and employing patch and notch antenna elements, are considered for different phase excitations. Using free space power density as the exposure metric, the maximum permissible transmitted power of UE, compliant with the maximum permissible exposure limits specified by the U.S. Federal Communications Commission (FCC) and the basic restrictions of the International Commission on Non-Ionizing Radiation Protection, is determined. The accuracy of different measurement schemes is assessed using numerical simulation. Verifying measurements is carried out in a semiane-choic chamber. The results indicate that, for UE employing array antennas and intended to be used in immediate vicinity of the human body, scalar measurement systems used in combination with straightforward field combination techniques will lead to overly conservative results. A more accurate and less conservative approach for these products is to conduct separate measurements for different excitations in order to span the space of possible excitations. This will result in a more complicated measurement setup and increase the measurement time, which points to a need for very fast measurement systems.

  • 25.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. SONY Mobile Communications AB, Sweden.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hu, J.
    Investigation of surface waves suppression on 5G handset devices at 15 GHz2016In: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7481336Conference paper (Refereed)
    Abstract [en]

    The challenge of surface wave excitation and propagation to millimeter-wave (mm-wave) antennas of future fifth-generation (5G) cellular system is addressed in this paper. This paper presents three different schemes by simulation, including mushroom-like electromagnetic band-gap (EBG) structures, cross-shaped resonant structures and T-shaped wave trap structures, to suppress surface wave propagation in handset devices at 15 GHz. We also investigate the positional influence of EBG structures on the radiation patterns of two slot array antennas on a mock-up. The measurement results suggest that gain, sidelobe level and radiation efficiency are all increased when the EBG structures are placed close to the radiating element.

  • 26.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Zhao, Kun
    Sony Mobile Commun, Network Technol Lab, Res & Technol, SE-22188 Lund, Sweden.;Aalborg Univ, Dept Elect Syst, Antennas Propagat & Radio Networking Sect, DK-9220 Aalborg, Denmark..
    Ying, Zhinong
    Sony Mobile Commun, Network Technol Lab, Res & Technol, SE-22188 Lund, Sweden..
    Sjoberg, Daniel
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    He, Wang
    Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Analysis of Impacts of Expected RF EMF Exposure Restrictions on Peak EIRP of 5G User Equipment at 28 GHz and 39 GHz Bands2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 20996-21005Article in journal (Refereed)
    Abstract [en]

    Above 6 GHz, radio frequency (RF) electromagnetic field (EMF) exposure from the mobile communication user equipment (UE) should be assessed in terms of incident power density, rather than specific absorption rate as below 6 GHz. Such regulatory RF EMF restrictions will constrain the transmit power of the UE and its peak equivalent isotropically radiated power (EIRP). This paper provides an analysis of the peak EIRP levels of UE containing code-book-based beamforming arrays at 28 GHz and 39 GHz. Different types of antenna elements, incremental element spacing, 4- and 8-element array configurations, and realistic housing integration are considered. The analysis and results show that in realistic housing integration, the 3GPP requirements on minimum peak EIRP can be generally met under the expected RF EMF exposure restrictions.

  • 27. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Yang, Li
    Mingorance, Alba
    Ruan, Changqing
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Wang, Linqin
    Vlachopoulos, Nick
    Lira-Cantu, Monica
    Boschloo, Gerrit
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Johansson, Erik M. J.
    Incorporation of Counter Ions in Organic Molecules: New Strategy in Developing Dopant-Free Hole Transport Materials for Efficient Mixed-Ion Perovskite Solar Cells2017In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 7, no 14, article id 1602736Article in journal (Refereed)
    Abstract [en]

    Hole transport matertial (HTM) as charge selective layer in perovskite solar cells (PSCs) plays an important role in achieving high power conversion efficiency (PCE). It is known that the dopants and additives are necessary in the HTM in order to improve the hole conductivity of the HTM as well as to obtain high efficiency in PSCs, but the additives can potentially induce device instability and poor device reproducibility. In this work a new strategy to design dopant-free HTMs has been presented by modifying the HTM to include charged moieties which are accompanied with counter ions. The device based on this ionic HTM X44 dos not need any additional doping and the device shows an impressive PCE of 16.2%. Detailed characterization suggests that the incorporated counter ions in X44 can significantly affect the hole conductivity and the homogeneity of the formed HTM thin film. The superior photovoltaic performance for X44 is attributed to both efficient hole transport and effective interfacial hole transfer in the solar cell device. This work provides important insights as regards the future design of new and efficient dopant free HTMs for photovotaics or other optoelectronic applications.

  • 28.
    Zhang, Wei
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Wang, Linqin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Guo, Yu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Zhang, Biaobiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Leandri, Valentina
    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.
    Li, Zhuofeng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Single crystal structure and opto-electronic properties of oxidized Spiro-OMeTAD2020In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 56, no 10, p. 1589-1592Article in journal (Refereed)
    Abstract [en]

    Single crystals of Spiro(TFSI)2 were grown, the optical and electronic properties were characterized and compared with neutral Spiro-OMeTAD. Density-functional theory was used to get insights into binding and band structure properties. The flat valence bands indicate a rather limited orbital overlap in Spiro(TFSI)2.

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