Enhanced Hole Transportation for Inverted Tin‐Based Perovskite Solar Cells with High Performance and Stability

Abstract

High electronic quality perovskite films with a balanced charge transportation is critical for satisfying high‐performance for perovskite solar cells (PVSCs). However, the inferior band alignment of tin‐based perovskite films with an adjacent hole‐transport layer (HTL) leads to a poor hole transportation and collection. In this work, the semiconducting molecule poly[tetraphenylethene 3,3′‐(((2,2‐diphenylethene‐1,1‐diyl)bis(4,1‐phenylene))bis(oxy))bis(N,N‐dimethylpropan‐1‐amine)tetraphenylethene] (PTN‐Br) is introduced into a lead‐free perovskite precursor to form a bulk heterojunction film. In addition, the PTN‐Br molecule with the suitable highest occupied molecular orbital energy level (−5.41 eV) can fill into the grain boundaries of the perovskite film, serving as a hole‐transport medium between grains. The gradient band alignment of the perovskite film with poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL ensures excellent hole transportation and higher open‐circuit voltage. In addition, the π‐conjugated polymer PTN‐Br can passivate trap states within the perovskite film due to the formation of Lewis adducts between uncoordinated Sn atoms and the dimethylamino of PTN‐Br. Consequently, a champion efficiency of 7.94% is achieved with significant enhancements in the open‐circuit voltage and fill factor. Furthermore, the PTN‐Br incorporated device shows better ultra violet (UV) stability because of the UV barrier and passivating effect of PTN‐Br, retaining about 66% of its initial efficiency after 5 h of continuous UV light irradiation.