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

Abstract

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 Pb²⁺ 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 cm² V⁻¹ s⁻¹ and the hole defect density is decreased by 41%, from 4.42 × 10¹⁵ to 2.63 × 10¹⁵ 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.