A fused-ring based electron acceptor for efficient non-fullerene polymer solar cells with small HOMO offset

A non-fullerene electron acceptor bearing a novel backbone with fused 10-heterocyclic ring (indacenodithiopheno-indacenodiselenophene), denoted by IDTIDSe-IC was developed for fullerene free polymer solar cells. This molecule exhibits low band gap (Eg=1.52 eV), strong absorption in the 600-850 nm region. When using a large band gap polymer J51 (Eg=1.91 eV) as donor, complementary absorption of the polymer donor and acceptor was obtained. The PSC based on J51:IDTIDSe-IC gives a high PCE of 8.02% with a VOC of 0.91 V, a JSC of 15.16 mA cm−2 and a FF of 58.0%. Moreover, the HOMO difference between J51:IDTIDSe-IC is as small as ~0.1 eV, which indicates the small driving force for hole transfer.195