Water-resistant 2D lead(ii) iodide perovskites: correlation between optical properties and phase transitions

The hybrid perovskite-based solar cells have achieved photovoltaic efficiencies comparable to that of the silicon-based solar cells; however, the light-absorbing perovskite materials are not stable and undergo rapid degradation in the presence of moisture. There are only a few water-stable 2D perovskite materials that have been explored so far. Keeping this in mind, we incorporated 3 different long-chain alkylammonium cations in 2D perovskites using a generic solution synthesis route where the saturated precursor solution was slowly cooled down to room temperature resulting in the single crystals of the 2D perovskites and studied their optical properties and stability against moisture. The prepared 2D perovskites demonstrated robust stability under ambient conditions as well as resistance to water. The main highlight of the present study is 2D perovskites emit bright green light in the 494-520 nm range even in the presence of water. We anticipate that our results on the water stable perovskite will not only motivate the use of these long alkyl chain cation-based 2D perovskite materials in perovskite solar cells for achieving the prolonged device stability but also for the next generation LEDs and display technologies.