Ga-doped ZnO as an electron transport layer for PffBT4T-20D: PC70BM organic solar cells

Ga-doped ZnO(GZO) is investigated as an electron transport layer in organic solar cells based on a promising donor: acceptor system of polyl(5,6-difluoro-2,1,3-benzothiadiazo1-4,7-diy1)-alt-(3,3"'-di(2-octyldode-cyl)-2,2'; 5',2";-5",2"'-quaterthio-phen-5,5"'-diyI)I (PffBT4T-20D):phenyl-C71-butyric acid methyl ester (PC70BM). With the inverted geometry having a configuration of ITO/GZO (40 nm)/13ffBT4T20D:PC70BM (270 nm)/MoO3 (20 nm)/AI (100 nm), maximum power conversion efficiency (PCE) of 9.74% has been achieved, while it is limited at 8.72% for devices with undoped ZnO. Our study based on the structural, morphological, compositional, and electrical characterizations indicate that suggests enhanced device performance of the GZO-based devices resulted mainly from the improved electrical properties of Ga-ZnO thin films as compared to undoped ZnO. (C) 2017 Elsevier B.V. All rights reserved.