Hydrogen bond induced high performance ternary fullerene-free organic solar cells with increased current density and enhanced stability

Abstract

Ternary bulk heterojunctions (BHJs) are efficient platforms for improving organic solar cell (OSC) performance. The third component in ternary OSCs is generally chosen such that it exhibits complementary absorption in the solar spectrum. There are few reports on the effect of the intermolecular action between the third component and the binary system. In this paper, two coumarin derivatives with a similar absorption spectrum, coumarin 7 (C7) and coumarin 30 (C30), were used as the third component to achieve ternary fullerene-free OSCs based on the PTB7-Th:ITIC system. As a result, ternary OSCs with 10 wt% C7 display a power conversion efficiency (PCE) of 10.16%, representing a 35% enhancement in comparison with the control device without C7 (7.50%). Moreover, the optimal ternary OSCs show enhanced thermal stability and photo-stability than the binary devices. In comparison, the ternary OSCs containing C30 showed poor performance and stability compared with C7 based ternary cells. The distinct improvements are ascribed to the elevated charge transfer ability and the optimized morphology of the photoactive layer due to the existence of hydrogen bonds, which formed between C7 and ITIC. This study indicates that introducing hydrogen bonds is a promising strategy to fabricate high performance and stable OSCs.