Oxygen Degradation in Mesoporous Al₂O₃/CH₃NH₃PbI₃<i>_x</i>Cl<i>_x</i> Perovskite Solar Cells: Kinetics and Mechanisms

DOI: 10.1002/aenm.201600014 unexpectedly clean electronic properties of these semiconductors have led to the demonstration of proof-of-concept PV devices with an initial effi ciency that outperforms competing ‘next-generation’ technologies such as dye-sensitized, organic, and quantum dot solar cells, and even matches that of commercially deployed PV. [ 6 ] Other attractive characteristics of hybrid perovskites include the low embedded costs of materials processing and the ability to tune the properties of the semiconductor through changes in chemical composition. [ 1,7–10 ] All of these factors have led to hybrid perovskites being considered as disruptive materials in a wide range of technology applications; [ 11–16 ] interest from the materials science research community is both substantial and rapidly maturing. Realizing the technology potential of hybrid perovskites necessitates a thorough understanding of the degradation mechanisms that limit the lifetime of devices, and identifying solutions to mitigate these. This exercise is nontrivial because of the various factors that can affect device performance: light, heat, moisture, oxygen, mechanical and electrical stresses, and combinations thereof. [ 17,18 ] Currently, perovskite solar cells (PSCs) based on the “triple layer” architecture with a thick carbon back electrode have demonstrated perhaps the most stable performance characteristics of all PSCs. [ 19 ] These devices, based on the mixed cation perovskite (5-AVA) X (MA) 1− X PbI 3 (where 5-AVA corresponds to 5-ammoniumvaleric acid), have been shown to maintain their initial power conversion effi ciency (PCE) of approximately 10% over 1000 h continuous simulated solar illumination, [ 20 ] dark storage for three months at elevated temperatures and humidity (85 °C/85%) and a minimum of 7 d operation in real-world conditions (Jeddah, Saudi Arabia). [ 21 ]