How the Mixed Cations (Guanidium, Formamidinium, and Phenylethylamine) in Tin Iodide Perovskites Affect Their Charge Carrier Dynamics and Solar Cell Characteristics
Eita Nakanishi, Ryosuke Nishikubo, Atsushi Wakamiya, Akinori Saeki
Abstract
Despite recent interest in lead-free Sn iodide perovskite (ASnI3) solar cells, the role of mixed A-site cations is yet to be fully understood. Here, we report the effect of the ternary mixing of organic A-site cations (guanidium, GA; formamidinium, FA; and phenylethylamine, PEA) on the solar cell performance and charge carrier dynamics that are evaluated using time-resolved microwave conductivity (TRMC). (GAxFA1–x)0.9PEA0.1SnI3 exhibits the maximum power conversion efficiency (PCE) of 7.90% at x = 0.15 and a drastic decrease with increasing GA content. Notably, our TRMC measurements of ASnI3 with/without a hole transport layer reveal the same trend with the devices. From the analyses, we suggest that a variation of electron mobility affected by the location of the GA cation in the grains significantly impacts the PCE. Our work sheds light on the role of mixed A-site cations and directs a route toward the further development of Sn perovskite solar cells.