Achieving organic solar cells with efficiency over 14% based on a non-fullerene acceptor incorporating a cyclopentathiophene unit fused backbone

The cyclopentadithiophene (CPT) unit is a classic building block for constructing organic semiconductor materials with excellent performances. In this work, we designed and synthesized a new acceptor BCPT-4F, incorporating a CPT fused central backbone. BCPT-4F shows a redshift absorption in the near-infrared region compared with CPT based acceptors with an unfused backbone. Importantly, the photovoltaic device based on PBDB-T:BCPT-4F achieved a promising power conversion efficiency (PCE) of 12.43% with a high short circuit current density (J(sc)) of 22.96 mA cm(-2). Furthermore, based on the above binary device, a ternary device with F-Br as the third component achieved a high PCE of 14.23%, which is presently the highest efficiency for devices with CPT based photovoltaic materials.