Tuning the Amount of Oxygen Vacancies in Sputter‐Deposited SnO_<i>x</i> films for Enhancing the Performance of Perovskite Solar Cells

Abstract

This work demonstrates the effect of oxygen vacancies in SnO_x thin films on the performance of perovskite solar cells. Various SnO_x films with different amounts of oxygen vacancies were deposited by sputtering at different substrate temperatures (25-300 °C). The transmittance of the films decreased from 82 to 66 % with increasing deposition temperature from 25 to 300 °C. Both X-ray photoelectron spectroscopy and electron-spin resonance spectroscopy confirmed that a higher density of oxygen vacancies was created within the SnO_x film at a high substrate temperature, which caused narrowing of the SnO_x bandgap from 4.1 (25 °C) to 3.74 eV (250 °C). Combined ultraviolet photoelectron spectroscopy and UV/Vis spectroscopy showed an excellent conduction band position alignment between the methylammonium lead iodide perovskite layer (3.90 eV) and the SnO_x electron transport layer deposited at 250 °C (3.92 eV). As a result, a significant enhancement of the open-circuit voltage from 0.82 to 1.0 V was achieved, resulting in an increase of the power conversion efficiency of the perovskite solar cells from 11 to 14 %. This research demonstrated a facile approach for controlling the amount of oxygen vacancies in SnO_x thin films to achieve a desirable energy alignment with the perovskite absorber layer for enhanced device performance.