(135e) Atomic Layer Deposition of Metal Oxides for More Stable Operation of Perovskite Solar Cells

The power conversion efficiency (PCE) of metal halide perovskite solar cells has shown rapid improvement since their inception over a decade ago, recently surpassing 25%. Now, stabilizing these devices for long-term operation is critical to their future commercial success. In addition to good external encapsulation, engineering contact layers and their interfaces with the perovskite absorber are important to achieving this goal. Atomic layer deposition (ALD) has emerged as a powerful tool for the growth of these contact layers due to the nanoscale control it affords over film thickness and composition. In this work, we demonstrate the significant impact that ALD metal oxide contacts can have on improving the long-term operational stability of perovskite solar cells. We also identify strategies to improve the barrier properties of these ALD films by tailoring their growth surface. Unencapsulated, single-junction devices with metal electrodes that incorporate ALD SnO₂ electron contacts exhibit high initial PCEs (up to 18.5%), and maintain, on average, 82% of their initial PCE following 250 hours of continuous, illuminated operation at maximum power in air at 60 °C. This result is a marked improvement over devices with only organic contacts, which lose all PCE after only 20 hours in the same harsh testing conditions. The vapor deposition strategies we employ in this work can be applied to various perovskite solar cell designs, including tandem or non-planar devices, and provide a framework for improving the quality of barrier/encapsulation layers in other optoelectronic and energy technologies.