Improving the Open‐Circuit Voltage of Low‐Dimensional Perovskite Solar Cells with NiOx Films by Interfacial Energy Level Alignment

Interface engineering strategy plays an essential role in improving the photovoltaic performance of perovskite solar cells (PSCs). In this study, nickel oxide (NiOx) films are fabricated by the low‐temperature combustion method and modified by poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) solution with a low concentration. Then, NiOx and NiOx/PTAA films are used as hole transport layers to fabricate low‐dimensional perovskite (4FPEA)2(MA0.9FA0.1)3Pb4I13 (n=4) (4FPEA: 4‐fluorophenylethylammonium, MA: methylammonium, FA: formamidinum). The experimental results show that the energy level alignment has been optimized by introducing a PTAA layer, which is beneficial to improving the hole extraction efficiency. Therefore, the low‐dimensional PSC exhibit the high open‐circuit voltage (1.21 V) by suppressing the non‐radiative recombination. Compared with the PSC based on NiOx film, the power conversion efficiency of the PSC based on NiOx/PTAA film is improved from 6.13 % to 12.25 %. Meanwhile, the PSC based on NiOx/PTAA film remains at 88 % of the initial efficiency after being stored in a nitrogen glove box for 900 h. Our work offers a promising route for applying NiOx film in low‐dimensional PSCs. Nickel oxide (NiOx) film is fabricated by the low‐temperature combustion method. The interfacial energy level alignment between NiOx film and low‐dimensional perovskite (4FPEA)2(MA0.9FA0.1)3Pb4I13 (4FPEA: 4‐fluorophenylethylammonium, MA: methylammonium, FA: formamidinum) film has been optimized by introducing a poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) layer. The perovskite solar cell based on NiOx/PTAA film achieves an efficiency as high as 12.25 % with a high open‐circuit voltage (Voc) of 1.21 V.