期刊
NANO ENERGY
卷 30, 期 -, 页码 639-648出版社
ELSEVIER
DOI: 10.1016/j.nanoen.2016.10.031
关键词
Organic solar cells; Solvent vapor annealing; Non-equilibrium morphology; Physical processes
类别
资金
- International Science & Technology Cooperation Program of China [2013DFG52740, 2010DFA52150]
- Ministry of Science and Technology [2014CB643500]
- National Natural Science Foundation of China [51473053, 51073060, 51225301, 91333206]
- U.S. Office of Naval Research [N00014-15-1-2244]
- DOE, Office of Science
- DOE, Office of Basic Energy Sciences
Solvent vapor annealing (SVA) studies on the morphology and performance of a porphyrin-based deep absorption organic solar cells consisting of a strongly segregated bulk heterojunction (BHJ) blend, are presented. It is seen that the solvent vapor annealing of a well-mixed BHJ blends induces molecular motion, leading to a phase separated morphology governed by a spinodal decomposition mechanism. The earlier stage of solvent vapor swelling (< 10 s) led to an obvious phase separation but not device performance. The device performance showed a dramatic increase in short circuit current and fill factor between 15 and 20 s of SVA. Thus, phase purity is a critical parameter in determining the performance of this binary blend. SVA on a thermally annealed BHJ thin film showed two distinctive processes, a crystal dissolution and a recrystallization, accompanied by phase mixing and then phase separation. The final morphology of SVA films that were initially thermally annealed showed a reduced length scale of phase separation, in comparison to SVA on as-cast films. Thus preformed donor crystallites appear to lock-in the morphology, even in a small molecule blend setting. The best performing device was obtained by a slight SVA (10 s) of films that were initially thermally annealed, reaching a power conversion efficiency of 8.48%. This suggests that the localized morphological optimization and domain size reduction are most important factors in dictating organic photovoltaic device efficiencies.
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