A highly efficient interface hole transporting tunnel by a bipyridine semiconductor for perovskite solar cells

Herein, we present a D-A-D type organic semiconductor with a bipyridine core for constructing an efficient tunnel between perovskite and a hole transporting layer to obtain high-performance PSCs. This molecule could facilitate the band bending of perovskite to construct energy level alignment. Moreover, its bipyridine core also passivates the uncoordinated Pb 2+ defects of perovskite films. Hence, the hole mobility of the hole transporting layer is increased by 7 times, from 1.05 × 10 −4 to 8.36 × 10 −4 cm 2 V −1 s −1 and the hole defect density is decreased by 41%, from 4.42 × 10 15 to 2.63 × 10 15 cm −3 after introducing this hole transporting tunnel. As a result, the power conversion efficiency (PCE) of n-i-p structured PSCs increases from 20.2% to 22.4% with improved stability. An efficient hole transport tunnel is constructed by a bipyridine based organic semiconductor that enables an increase of the hole mobility by seven times.