Enhanced Hole Transportation For Inverted Tin-Based Perovskite Solar Cells With High Performance And Stability

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 -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.