PbI2 Initiated Cross-Linking and Integration of a Polymer Matrix with Perovskite Films: 1000 h Operational Devices under Ambient Humidity and Atmosphere and with Direct Solar Illumination

The instability of organic lead halide perovskites such as MAPbI 3 under ambient conditions is a challenge, as it leads to degradation in device performance and has limited their long-term application. To address this, we use the Lewis acid nature of PbI 2, a key chemical for making MAPbI 3 perovskite (and others) for in situ cross-linking of polystyrene (PS) chains in the precursor solution. The resulting PS–perovskite devices without any encapsulating layer show a stable structure in ambient conditions after >1000 h of continuous 1.0 sun (AM 1.5G) illumination in air (relative humidity of 40–50%) at 45 °C, while also showing a slightly improved device performance. The stability is the result of the direct specific interaction between the polymer and the perovskite that reduces ion migration, charge recombination, trap-state density, and dark currents and at the same time leads to improve mobility and carrier lifetime. The interaction between the polymer and PbI 2 also improves the crystallization kinetics, leading to larger grain size in the perovskite films. The cumulative effect of these improvements makes the reported polymer–perovskite hybrids well suited for long-term device applications and presents a new avenue for making stable polymer–perovskite composites.