Jeffrey Christians1 Philip Schulz1 Tracy Schloemer2 Steve Harvey1 Bertrand Tremolet de Villers1 Alan Sellinger2 1 Joseph Berry1 Joseph Luther1

1, National Renewable Energy Laboratory, Lakewood, Colorado, United States
2, Colorado School of Mines, Golden, Colorado, United States

It has become clear in the past few years that the commercial success or failure of perovskite solar cells hinges upon thier stability. Thus, over the past few years research efforts focused on improving perovskite solar cell stability have greatly intensified. Recent work has provided insight into moisture instability, thermal instability, and phase instability of the halide perovskites themselves. Building off this important knowledge base, we begin with a standard TiO2/perovskite/sprio-OMeTAD/Au device architecture and then systematically investigate the degradation mechanisms associated with TiO2, spiro-OMeTAD, and Au, replacing each of these layers to mitigate identified degradation pathways. This work results in a detailed understanding of the major device-level degradation mechanisms and, importantly, their suppression. Ultimately, this strategy improves device stability by over 3 orders of magnitude. The final SnO2/perovskite/EH44/MoOx/Al device stack retains 94% (88% average) of its peak power conversion efficiency despite 1000 hrs of continual, unencapsulated operation in ambient conditions. This dramatic improvement in stability, despite the combined stresses of UV-light, oxygen, and moisture, demonstrates the importance of carefully designed interfaces for realizing true long-term perovskite solar cell stability.