Revealing and Eliminating the Light‐Soaking Issue in Metal Oxide‐Based Inverted Organic Solar Cells

Abstract

AbstractInverted organic solar cells (i‐OSCs) provide an exciting opportunity for commercialization owing to their excellent device air stability. However, light soaking (LS) issue generally occurs in metal oxide based i‐OSCs, causing drastically decreased performance. The underlying root of LS effect is not clearly clarified until now. Herein, it is demonstrated that the surface oxygen defects on metal oxide nanoparticles, such as chemisorbed superoxide (O2−) and hydroxide (OH) dangling bonds, are the main reasons for LS issue in i‐OSCs. The O2− layer induces band bending at the cathode interface and increases the work function (WF) of metal oxide, thus leading to inefficient charge transport. The dangling bonds serve as interfacial trap states and cause non‐radiative recombination, thus leading to the reduced open circuit voltage (Voc). With ultraviolet (UV) illumination, the surface oxygen defects are interacted with photogenerated carriers, thereby improving the photovoltaic performance. Additionally, UV pretreatment of metal oxide films is employed to eliminate the LS issue and the resulting device yields significantly improved fill factors from 50.20% to 73.50% in the pristine SnO2 based i‐OSCs. This study reveals the origin of LS effect in i‐OSCs and proposes a suggested model for LS mechanism.