Benzodithiophene-based small molecules with various termini as hole transporting materials in efficient planar perovskite solar cells

Abstract

In this study we prepared four benzodithiophene (BDT)-based small organic molecules presenting bithiophene (TT), thiophene (FT), carbazole (CB), and triphenylamine (TPA) units, respectively, as termini, and used them as hole transporting materials for perovskite solar cells (PSCs). The high degrees of planarity of these BDT-based small molecules imparted them with high degrees of stacking and charge transport. These small molecules had suitable optical properties and energy level alignments for use in PSCs based on MAPbI 3 , with compact-TiO 2 as the electron transporting layer and a BDT-based material as the hole transporting layer, in a n–i–p structure. Among our tested BDT-based materials, the PSC incorporating BDT-TT had the best performance, with an average power conversion efficiency of 13.63%. The benzodithiophene (BDT) derivatives presenting bithiophene (TT), carbazole (CB), thiophene (FT), and triphenylamine (TPA) units based small molecules used them as hole transporting materials to fabricate planar perovskite solar cells. • We have prepared benzodithiophene (BDT) derivatives presenting bithiophene (TT), carbazole (CB), thiophene (FT), and triphenylamine (TPA) units and then used them as hole transporting materials to fabricate n–i–p PSCs. The power conversion efficiency of the device incorporating BDT-TT was the highest among our tested PSCs. • The film of the small molecule BDT-TT had the best morphology among our tested BDT-based HTMs, suggesting that TT units might be useful components when designing new hole transporting materials for high-performance PSCs. • Additives improved the performance of our PSCs by increasing the mobilities in the hole transporting materials, thereby achieving higher power conversion efficiencies.