Hsieh, Tzu-ChienTzu-ChienHsiehShih, Chung-YuehChung-YuehShihChao, Yu-ChiangYu-ChiangChaoI-CHUN CHENGJIAN-ZHANG CHEN2022-03-222022-03-22202120462069https://www.scopus.com/inward/record.uri?eid=2-s2.0-85108347969&doi=10.1039%2fd1ra02574k&partnerID=40&md5=c8409cfabb72404d7dfdf4271b05f45chttps://scholars.lib.ntu.edu.tw/handle/123456789/598803Two-dimensional perovskite solar cells (2-D PSCs) have attracted much research attention in recent years because they are more stable in a regular environment than three-dimensional (3-D) ones are. In this study, we doped Cs into 2D perovskite (BA2(MA)2Pb3I10) films as the absorbing layers of the 2-D p-i-n inverted PSCs to investigate the influence of the Cs doping concentration on the properties of the 2-D perovskite films and the fabricated solar cells. Cs doping clearly improves the power conversion efficiency (PCE) and air stability of the PSCs. Doping perovskite with 10% Cs (the best doping concentration in this study) can increase the PSC efficiency from 7.98% to 10.11%. Scanning electron microscopy indicates the improved surface quality and crystallinity by Cs doping. However, excess Cs doping degrades the PCE of the PSCs. Furthermore, 10% Cs doped PSCs show air stability superior to that of undoped ones in unpackaged humidity environments. After exposure to 55% relative humidity (RH) in 19 °C air for 300 h, the PCE of the PSC decreased by only 39%, in contrast to 84% for the undoped PSC. ? The Royal Society of Chemistry 2021.CesiumConversion efficiencyCrystallinityEfficiencyPerovskiteScanning electron microscopySemiconductor dopingAbsorbing layersAir stabilityDoping concentrationPerovskite filmsPower conversion efficienciesThreedimensional (3-d)Perovskite solar cells[SDGs]SDG7journal article10.1039/d1ra02574k2-s2.0-85108347969