The Influence of Fluorination on Nano-Scale Phase Separation and Photovoltaic Performance of Small Molecular/PC71BM Blends.
To investigate the fluorination influence on the photovoltaic performance of small molecular based organic solar cells (OSCs), six small molecules based on 2,1,3-benzothiadiazole (BT), and diketopyrrolopyrrole (DPP) as core and fluorinated phenyl (DFP) and triphenyl amine (TPA) as different terminal units (DFP-BT-DFP, DFP-BT-TPA, TPA-BT-TPA, DFP-DPP-DFP, DFP-DPP-TPA, and TPA-DPP-TPA) were synthesized. With one or two fluorinated phenyl as the end group(s), HOMO level of BT and DPP based small molecular donors were gradually decreased, inducing high open circuit voltage for fluorinated phenyl based OSCs. DFP-BT-TPA and DFP-DPP-TPA based blend films both displayed stronger nano-scale aggregation in comparison to TPA-BT-TPA and TPA-DPP-TPA, respectively, which would also lead to higher hole motilities in devices. Ultimately, improved power conversion efficiency (PCE) of 2.17% and 1.22% was acquired for DFP-BT-TPA and DFP-DPP-TPA based devices, respectively. These results demonstrated that the nano-scale aggregation size of small molecules in photovoltaic devices could be significantly enhanced by introducing a fluorine atom at the donor unit of small molecules, which will provide understanding about the relationship of chemical structure and nano-scale phase separation in OSCs.
College of Chemistry and Environmental Engineering, ShanXi DaTong University, Datong 037009, China. luzhen0313@aliyun.com.
Zhen
Z
Lu
College of Chemistry and Environmental Engineering, ShanXi DaTong University, Datong 037009, China. liuwen19701021@163.com.
Wen
W
Liu
College of Chemistry and Environmental Engineering, ShanXi DaTong University, Datong 037009, China. lijingjing8150@163.com.
Jingjing
J
Li
Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, China. fangtao@bnu.edu.cn.
Tao
T
Fang
College of Chemistry and Environmental Engineering, ShanXi DaTong University, Datong 037009, China. liwanning2016@163.com.
Wanning
W
Li
Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, China. zhangjichengbnu@hotmail.com.
Jicheng
J
Zhang
College of Chemistry and Environmental Engineering, ShanXi DaTong University, Datong 037009, China. feng-feng64@263.net.
Feng
F
Feng
Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, China. liwenhua@bnu.edu.cn.
Wenhua
W
Li
fluorinated phenyl (DFP) groups; nanoscale phase separation; organic solar cell; small molecule; solution process