Efficient small molecule photovoltaic donor based on 2,3-diphenyl-substituted quinoxaline core for solution-processed organic solar cells

A novel D–π–A–π–D-type organic small molecule (OSM) named (TPACN)2Qx was designed and synthesized for solution-processible organic solar cells (OSCs), which contained 2,3-diphenyl-substituted quinoxaline (Qx) as the central acceptor (A) unit, triphenylamine (TPA) as terminal electron-donor (D) moieties, and acrylonitrile as the π-linkage segment. With an effective electron-withdrawing property and relatively stable quinoid geometry of Qx, (TPACN)2Qx exhibits a narrow band-gap of 1.88 eV and strong and broad absorption at 300–700 nm. As a consequence, an excellent power conversion efficiency (PCE) of 6.25% was achieved based on the (TPACN)2Qx:PC61BM blend using a simple spin-coating process in a solution, which is the highest efficiency achieved to date for Qx-core based solution-processed OSM photovoltaic (PV) devices. The impressive result demonstrates that OSMs employing quinoxaline derivative as an electrophilic unit can compete with their polymer counterparts.