A simple-structure small-molecule acceptor enables over 18% efficiency ternary polymer solar cells with a broad composition tolerance

Abstract

A ternary structure is considered as one of the most promising strategies to boost power conversion efficiency (PCE) of polymer solar cells (PSCs). Herein, a simple-structure small-molecule non-fullerene acceptor IDIC-C4Ph with an indaceno[2,1-b:6,5-b']dithiophene unit (IDT) core was primarily used as a guest acceptor and incorporated into the PM6:Y6 blend to construct ternary PSCs. The influence of IDIC-C4Ph on optoelectronic properties and photovoltaic performance of ternary PSCs were systematically studied. It was found that the IDIC-C4Ph had a complementary absorption with the PM6:Y6 blend in the range of 590–710 nm and a higher lowest unoccupied molecular orbital (LUMO) than Y6. As a result, this guest acceptor endowed the ternary PSCs based on PM6:Y6:IDIC-C4Ph system with a remarkably increasing open-circuit voltage (Voc) of 0.87 V and lower energy loss of 0.53 eV in comparison with the binary PSCs based on PM6:Y6 system. And an outstanding PCE of 18.10% with simultaneously increased Jsc of 26.65 mA cm−2 and FF of 77.85% was achieved in the PM6:Y6:IDIC-C4Ph based PSCs. Importantly, the ternary PSCs exhibited a broad composition tolerance to Y6:IDIC-C4Ph ratios ranging from 1.2:0.10 to 1.2:0.50 with a PCE higher than the PM6:Y6 based PSCs and an improved device stability, in which the PCE value maintained 90% level after 1080 h (45 days) at room temperature. Our work indicates that the IDIC-C4Ph is a promising guest acceptor to boost photovoltaic performance and device stability in the ternary PSCs.