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Impact of Polymer Backbone Fluorination on the Charge Generation/Recombination Patterns and Vertical Phase Segregation in Bulk Heterojunction Organic Solar Cells
Shao, Yanqiu1; Chang, Yuying1; Zhang, Suju1; Bi, Mingyue1; Liu, Shengjian2; Zhang, Daliang3; Lu, Shirong4; Kan, Zhipeng4
2020-03-05
摘要Incorporating fluorine (-F) substituents along the main-chains of polymer donors and acceptors is an effective strategy toward efficient bulk-heterojunction (BHJ) solar cells. Specifically, F-substituted polymers often exhibit planar conformations, leading to favorable packing, and electronic coupling. However, the effects of fluorine substituents on the charge generation and recombination characteristics that determine the overall efficiency of BHJ active layers remain critically important issues to examine. In this report, two PBDT[2X]T polymer analogs -poly[4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4, 5-b ']dithiophene-thiophene] [PBDT[2H]T] and its F-substituted counterpart poly[4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b ']dithiophene-3,4-difluoro-thiophene] [PBDT[2F]T]-are studied to systematically examine how -F substituents impact the blend morphology, charge generation, carrier recombination and extraction in BHJ solar cells. Considering the large efficiency differences between PBDT[2H]T- and PBDT[2F]T-based BHJ devices, significant emphasis is given to characterizing the out-of-plane morphology of the blend films as vertical phase-separation characteristics are known to have dramatic effects on charge transport and carrier extraction in polymer-fullerene BHJ solar cells. Herein, we use electron energy loss spectroscopy (EELS) in tandem with charge transport characterization to examine PBDT[2X]T-fullerene blend films. Our analyses show that PBDT[2H]T and PBDT[2F]T possess very different charge generation, recombination and extraction characteristics, resulting from distinct aggregation, and phase-distribution within the BHJ blend films.
关键词bulk heterojunction polymer backbone fluorination charge generation and recombination vertical phase segregation organic solar cells
DOI10.3389/fchem.2020.00144
发表期刊FRONTIERS IN CHEMISTRY
ISSN2296-2646
卷号8页码:8
通讯作者Shao, Yanqiu(shaoyanqiu1969@163.com) ; Kan, Zhipeng(kanzhipeng@cigit.ac.cn)
收录类别SCI
WOS记录号WOS:000525093400001
语种英语