Influence of organic cations on intrinsic properties of lead iodide perovskite solar cells

A comprehensive study of the intrinsic properties including internal absorption, charge recombination and internal quantum efficiency of lead iodide perovskite solar cells (PeSCs) based on CH3NH3PbI3 (MAPbI3) and HC(NH2)2PbI3 (FAPbI3) perovskites is presented. The optical simulation of PeSCs shows that FAPbI3 layer exhibits a wider internal absorption spectra than MAPbI3 layer due to its lower bandgap determined by ultraviolet photoemission spectroscopic (UPS) and band structure calculation. The photo-induced charge extraction by linearly increasing voltage (photo-CELIV) investigation and photocurrent density (Jph) versus effective voltage (Veff) measurement indicate that FAPbI3 PeSCs possess lower charge recombination and higher charge collection efficiency because of the superior transport property of FAPbI3 perovskite, leading to higher internal quantum efficiency (IQE) than MAPbI3 PeSCs. In addition, by comparing the calculated short-circuit current (JSC) by Spectroscopic Limited Maximum Efficiency (SLME) mathematical models, the predicted JSC by transfer matrix optical model (TMM) and the experimental JSC from current density versus voltage (J-V) characteristics, we find that the light losses from the absorption of non-perovskite layers and the reflection at the incident interface of device, and the charge recombination in perovskite layer are the main factors limiting the photocurrent of PeSCs based on these two perovskites.