Pyran-bridged A-D-A type small molecular acceptors for organic solar cells

Pyran is fused into the planar donor moiety to enhance the extinction coefficient and reduce the bandgap, thus two acceptors PTTIC and PTBT-R are designed and synthesized. Compared to the IDT-based acceptor, these pyran-bridged acceptors show higher the highest occupied molecular orbital level and wider absorption coverage. Devices fabricated with poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione)] (PBDB-T):PTTIC as the active layer give a power conversion efficiency (PCE) of 7.35%.