A cyclopentadithiophene-bridged small molecule acceptor with near-infrared light absorption for efficient organic solar cells

A cyclopentadithiophene (DTC)-bridged acceptor–donor–acceptor (A–D–A) backboned small molecule acceptor (SMA), namely IDTC-4Cl, was designed and synthesized. In combination with strong electron-withdrawing (5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)dimalononitrile as a terminal group, IDTC-4Cl exhibits a near-infrared light absorption with an edge over 900 nm. Using PBDB-T as the polymer donor, the IDTC-4Cl based device gives a PCE of 9.51% with a Voc of 0.822 V, FF of 60.2% and Jsc of 19.14 mA cm−2. Upon introduction of PC71BM as the third component, the ternary OSCs show an enhanced PCE of 10.41% with a much improved FF of 65.6%, which exemplifies the potential of utilizing a DTC unit to construct an SMA for high-performance organic photovoltaics.