Extrinsic Electron Concentration in SnO 2 Electron Extracting Contact in Lead Halide Perovskite Solar Cells

Lead halide perovskite solar cells that use SnO 2 as the electron‐transporting material are known to improve upon light soaking. Photoluminescence measurements and electrochemical impedance spectroscopy show that this improvement is due to reduced non‐radiative recombination and is accompanied by a reduction in the extrinsic electron concentration in SnO 2 . This performance enhancement can also be achieved by exposing these devices to high vacuum at ambient temperature. This study postulates that the performance increase stems from desorption of hydrogen from oxygen vacancies in SnO 2 . Furthermore, Ga‐doped SnO 2 ‐based devices exhibit a reduced light‐soaking effect and have fewer oxygen vacancies, as is shown by X‐ray photoelectron spectroscopy measurements. It is concluded that high extrinsic electron concentrations in SnO 2 are undesirable because of their role in non‐radiative recombination. The reduction in electron density when SnO 2 is incorporated into a perovskite diode is therefore advantageous for solar cell performance.