High-performance ternary polymer solar cells from a structurally similar polymer alloy

Abstract

High-efficiency ternary polymer solar cells (PSCs) are fabricated by using two donor polymers (PBDTTPD and PBDTTT-C-T) with similar polymer backbones and complementary absorption and PC₇₁BM as the acceptor. A high power conversion efficiency (PCE) of 9.3% is achieved with a high short-circuit current density (J_sc) of 17.2 mA cm⁻². The enhanced J_sc and PCEs are mainly attributed to the broadened photoresponse of the ternary blend. Good miscibility of the two donor polymers is found due to the similar polymer main chains, leading to the desired morphology between the donors and PC₇₁BM in the ternary blends. The trend of open-circuit voltage (V_oc) variations indicates the formation of a polymer alloy in this ternary blend. Our work demonstrates that using two donor polymers with similar backbone structures is a rational strategy for realizing high-performance ternary PSCs.