A large-bandgap small-molecule electron acceptor utilizing a new indacenodibenzothiophene core for organic solar cells

Abstract

A weak electron-donating ladder-type heteroarene, indacenodibenzothiophene (IDBT), is designed and synthesized for the development of acceptor–donor–acceptor (A–D–A)-type small-molecule acceptors featuring a large optical bandgap to match high-performance low-bandgap electron donors. Small-molecule acceptor NIDBT based on the IDBT core and 2-(2,3-dihydro-3-oxo-1H-inden-1-ylidene)propanedinitrile as an electron-deficient end group is designed and synthesized. NIDBT shows a wide optical bandgap of 1.84 eV with a high absorption coefficient. A low-bandgap polymer PTB7-Th is selected as the donor to construct photovoltaic devices with NIDBT as the acceptor. After a thermal-annealing treatment at 160 °C for 10 min, an optimal power conversion efficiency (PCE) of 4.45% with an open-circult voltage (V_oc) of 0.831 V, a short-circuit current (J_sc) of 11.45 mA cm⁻² and a fill factor (FF) of 46.73% is realized.