A solution-processed small molecule with optimal side chains for high efficiency non-fullerene organic solar cells

A novel small molecular electron donor with an optimized side group was synthesized for solution-processed organic solar cells . In order to extend the conjugation length in 2-dimensional structure, 5-alkylthio-thieno[3,2- b ]thiophene was attached onto the central benzo[1,2- b :4,5- b ’]dithiophene unit. The small molecule exhibited an optical energy gap of 1.71 eV, low-lying energy levels, strong intermolecular interaction in solid state, which result in promising power conversion efficiency up to 7.15% with ITIC as a non-fullerene electron acceptor . This work demonstrates the potential of optimal side chain of small molecular donor for high performance of solution-processed non-fullerene organic solar cells. • A novel small molecular organic semiconductor (TTSBDT(TDPP)2) was designed and synthesized. • TTSBDT(TDPP)2 exhibited low band gap and appropriate energy levels for non-fullerene organic solar cells. • Optimal condition of active layer showed a power conversion efficiency of 7.15%.