Efficient ternary organic solar cells with BT-rhodanine-based nonfullerene acceptors in a PM6:Y6-BO blend

A series of benzothiadiazole (BT)-rhodanine-based nonfullerene acceptors (NFAs) were designed and synthesized. These BT-rhodanine-based NFAs were composed of BT as a central core with a 3-octylthienothiohene pi-bridge and two different rhodanine end groups (BT-rho for octylrhodanine and BT-rhoCN for dicyano-octylrhodanine end groups). The highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels were -5.53/-3.78 eV for a BT-rho film and -5.63/-3.90 eV for a BT-rhoCN film. The strong electron-withdrawing dicyano-octylrhodanine end group of BT-rhoCN downshifted the HOMO and LUMO levels by similar to 0.1 eV compared with those of BT-rho. The 10% BT-rho in a PM6:Y6-BO ternary organic solar cell exhibit a maximum power conversion efficiency (PCE) of 16.17% with a short-circuit current density (J(SC)) of 25.29 mA cm(-2), open-circuit voltage (V-OC) of 0.84 V, and fill factor (FF) of 76.13%. The hole/electron mobilities of the PM6:Y6-BO, 10% BT-rho, and 10% BT-rhoCN ternary devices were 2.20 x 10(-4)/1.85 x 10(-4) cm(2) V-1 s(-1), 3.66 x 10(-4)/3.77 x 10(-4) cm(2) V-1 s(-1), and 1.34 x 10(-4)/0.94 x 10(-4) cm(2) V-1 s(-1), respectively. The crystal coherence lengths (L(C)s) of the (010) peaks for the PM6:Y6-BO, 10% BT-rho, and 10% BT-rhoCN ternary films are 43.2, 60.8, and 33.7 A, respectively. The superior PCE of the 10% BT-rho ternary devices compared with that of the PM6:Y6-BO binary device is attributed to the enhanced hole and electron mobilities and the high crystallinity of the blend films, which contribute to the enhancement of the J(SC) and PCE.

Automated summary

A series of BT-rhodanine-based nonfullerene acceptors (NFAs) were designed and synthesized, with BT-rhoCN showing lower HOMO and LUMO levels compared to BT-rho. The ternary organic solar cell with 10% BT-rho exhibited a higher PCE and enhanced hole and electron mobilities, as well as high crystallinity.