High performance opaque and semi-transparent organic solar cells with good tolerance to film thickness realized by a unique solid additive

Organic solar cells (OSCs) with high tolerance to film thickness are essential for high performance and low-cost commercial manufacturing. Most popular strategies acquire this feature by designing new donor or acceptor materials, which is too complicated and time-consuming. In this work, we provide a simple and efficient strategy that introduces a novel halogen-free solid additive, 1,10-decanediol (DDO), into the bulk heterojunction to realize highly efficient and thermostable OSCs with good tolerance to film thickness. The binary OSC based on PTB7-Th:PC71BM:0.5% DDO shows a high power conversion efficiency (PCE) of 10.11%, which is superior to that of the OSC doped with the traditional solvent additive 1,8-diiodooctane (DIO) (PCE of 9.44%). On co-doping DDO and DIO into the system, a maximum PCE of 11.64% was obtained for the binary OSC. Most importantly, the DDO-containing OSCs show a high tolerance to film thickness (80-300 nm), with a PCE ranging from 10.22% to 11.64%. This is attributed to the addition of DDO, which improved the crystallinity of the polymer, optimized the miscibility between donor and acceptor, and modulated the vertical distribution of molecules. Furthermore, considering the good tolerance to film thickness of the active layer, a semi-transparent OSC (ST-OSC) based on DDO achieves a high PCE of 8.41% with a high average visible transmittance (AVT) of 30.8%, and an optimized PCE of 9.71% with an AVT of 15.9%, which is among the best reported ST-OSCs. Moreover, the DDO-containing OSCs show excellent thermostability, with the PCE remaining at 73% of its original value after 120 min thermal annealing under atmospheric conditions. This work demonstrates an original and convenient strategy to fabricate high performance semi-transparent or thick-film OSCs.