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- Title
4,5-Ethylene-2,7-Carbazole-Based Medium-Bandgap Conjugated Polymers with Low-Lying HOMO Levels Toward Efficient Polymer Solar Cells with High Open-Circuit Voltage.
- Authors
Sun, Jiangman; Zhu, Yongxiang; Xu, Xiaofeng; Zhang, Chen; Chen, Junwu; Chen, Hongzheng; Cao, Yong
- Abstract
Three medium-bandgap polymers based on a 4,5-ethylene-2,7-dithienyl carbazole as the electron-donating unit and different 5,6-dialkoxy-2,1,3-benzothiadiazoles as the electron-accepting units, are synthesized as polymer donors for photovoltaic applications. The three copolymers possess highest occupied molecular oribital (HOMO) levels around −5.47 eV and medium bandgaps of about 1.94 eV. The solar cells with polymer:[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) = 1:4 as the active layer, show an especially high open-circuit voltage ( Voc) of 0.95 V and attain good power conversion efficiency up to 5.91%. The hole mobilities of the active layer films, measured by space-charge-limited current (SCLC), are up to 3.5 × 10−4 cm2 V−1 s−1. Given the favorable medium bandgaps, low-lying HOMO levels, and good hole mobilities, these copolymers are promising candidates for the construction of a highly efficient front cell to harvest the shorter wavelength band of the solar radiation in a tandem solar cell with high Voc.
- Subjects
BAND gaps; SOLAR cells; METHYL formate; SPACE-charge-limited conduction; COPOLYMERS
- Publication
Macromolecular Chemistry & Physics, 2014, Vol 215, Issue 11, p1052
- ISSN
1022-1352
- Publication type
Article
- DOI
10.1002/macp.201400001