Zhaojun Li
Chalmers University of Technology
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Publication
Featured researches published by Zhaojun Li.
Journal of the American Chemical Society | 2016
Zhaojun Li; Xiaofeng Xu; Wei Zhang; Xiangyi Meng; Wei Ma; Arkady Yartsev; Olle Inganäs; Mats R. Andersson; René A. J. Janssen; Ergang Wang
Growing interests have been devoted to the design of polymer acceptors as potential replacement for fullerene derivatives for high-performance all polymer solar cells (all-PSCs). One key factor that is limiting the efficiency of all-PSCs is the low fill factor (FF) (normally <0.65), which is strongly correlated with the mobility and film morphology of polymer:polymer blends. In this work, we find a facile method to modulate the crystallinity of the well-known naphthalene diimide (NDI) based polymer N2200, by replacing a certain amount of bithiophene (2T) units in the N2200 backbone by single thiophene (T) units and synthesizing a series of random polymers PNDI-Tx, where x is the percentage of the single T. The acceptor PNDI-T10 is properly miscible with the low band gap donor polymer PTB7-Th, and the nanostructured blend promotes efficient exciton dissociation and charge transport. Solvent annealing (SA) enables higher hole and electron mobilities, and further suppresses the bimolecular recombination. As expected, the PTB7-Th:PNDI-T10 solar cells attain a high PCE of 7.6%, which is a 2-fold increase compared to that of PTB7-Th:N2200 solar cells. The FF of 0.71 reaches the highest value among all-PSCs to date. Our work demonstrates a rational design for fine-tuned crystallinity of polymer acceptors, and reveals the high potential of all-PSCs through structure and morphology engineering of semicrystalline polymer:polymer blends.
Journal of the American Chemical Society | 2013
Deping Qian; Wei Ma; Zhaojun Li; Xia Guo; Shaoqing Zhang; Long Ye; Harald Ade; Zhan'ao Tan; Jianhui Hou
A novel polythiophene derivative, PBT1, was designed, synthesized, and applied in polymer solar cells (PSCs). This work provides a successful example of using molecular structure as a tool to realize optimal photovoltaic performance with high polymer content, thus enabling the realization of efficient photoabsorption in very thin films. As a result, an efficiency of 6.88% was recorded in a PSC with a 75 nm active layer.
Journal of Materials Chemistry | 2014
Xiaofeng Xu; Zhaojun Li; Olof Bäcke; Kim Bini; David Ian James; Eva Olsson; Mats R. Andersson; Ergang Wang
Four new D–A polymers PIDTT-Q-p, PIDTT-Q-m, PIDTT-QF-p and PIDTT-QF-m, using indacenodithieno[3,2-b]thiophene (IDTT) as an electron-rich unit and quinoxaline (Q) as an electron-deficient unit, were synthesized via a Pd-catalyzed Stille polymerization. The side chains on the pendant phenyl rings of IDTT were varied from the para- to the meta-position, and the effect of the inclusion of fluorine on the quinoxaline unit was simultaneously investigated. The influence on the optical and electrochemical properties, film topography and photovoltaic properties of the four copolymers were thoroughly examined via a range of techniques. The inductively electron-withdrawing properties of the fluorine atoms result in a decrease of the highest occupied molecular orbital (HOMO) energy levels. The effect of meta-substitution on the PIDTT-Q-m polymer leads to good solubility and in turn higher molecular weight. More importantly, it exhibits optimal morphological properties in the PIDTT-Q-m/PC71BM blends. As a result, the corresponding solar cells (ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al) attain the best power conversion efficiency (PCE) of 6.8%. The structure–property correlations demonstrate that the meta-alkyl-phenyl substituted IDTT unit is a promising building block for efficient organic photovoltaic materials. This result also extends our strategy with regards to side chain isomerism of IDTT-based copolymers for enhanced photovoltaic performance.
Journal of Materials Chemistry | 2017
Zhaojun Li; Xiaofeng Xu; Wei Zhang; Zewdneh Genene; Wendimagegn Mammo; Arkady Yartsev; Mats R. Andersson; René A. J. Janssen; Ergang Wang
In this work, we synthesized and characterized two new n-type polymers PTDPP-PyDPP and PIID-PyDPP. The former polymer is composed of pyridine-flanked diketopyrrolopyrrole (PyDPP) and thiophene-flanked diketopyrrolopyrrole (TDPP). The latter polymer consists of PyDPP and isoindigo (IID). PIID-PyDPP exhibits a much higher absorption coefficient compared to the widely used naphthalene diimide (NDI)-based acceptor polymers, and its high-lying LUMO level affords it to achieve a high open-circuit voltage (Voc). As a result, an all-polymer solar cell (all-PSC) fabricated from a high band gap polymer PBDTTS-FTAZ as the donor and PIID-PyDPP as the acceptor attained a high Voc of 1.07 V with a power conversion efficiency (PCE) of 4.2%. So far, it has been one of the highest PCEs recorded from all-PSCs using diketopyrrolopyrrole (DPP)-based acceptors. Gratifyingly, no obvious PCE decay was observed in two weeks, unraveling good stability of the all-PSC. This work demonstrates that the electron-withdrawing PyDPP unit can be a promising building block for new acceptor polymers in all-PSCs.
Journal of Physical Chemistry C | 2013
Shaoqing Zhang; Long Ye; Qi Wang; Zhaojun Li; Xia Guo; Lijun Huo; Huili Fan; Jianhui Hou
Energy and Environmental Science | 2017
Zhaojun Li; Xiaofeng Xu; Wei Zhang; Xiangyi Meng; Zewdneh Genene; Wei Ma; Wendimagegn Mammo; Arkady Yartsev; Mats R. Andersson; René A. J. Janssen; Ergang Wang
Advanced Energy Materials | 2017
Zhaojun Li; Wei Zhang; Xiaofeng Xu; Zewdneh Genene; Dario Di Carlo Rasi; Wendimagegn Mammo; Arkady Yartsev; Mats R. Andersson; René A. J. Janssen; Ergang Wang
Journal of Physical Chemistry C | 2017
Guangzheng Zuo; Zhaojun Li; Olof Andersson; Hassan Abdalla; Ergang Wang; M Martijn Kemerink
Advanced Energy Materials | 2018
Xiaofeng Xu; Zhaojun Li; Wei Zhang; Xiangyi Meng; Xianshao Zou; Dario Di Carlo Rasi; Wei Ma; Arkady Yartsev; Mats R. Andersson; René A. J. Janssen; Ergang Wang
Nano Energy | 2018
Xiaofeng Xu; Zhaojun Li; Junke Wang; Baojun Lin; Wei Ma; Yangjun Xia; Mats R. Andersson; René A. J. Janssen; Ergang Wang