Field‐Modulated Photoresponse in Dual‐Phase Perovskite Nanosheets for Photodetection Application

Layered perovskites are an excellent class of optoelectronic materials thanks to their high carrier mobility, tunable bandgap, enhanced chemical stability with flexible integration options even onto flexible substrates. Phase mixing of CsPbBr 3 with the layered CsPb 2 Br 5 is known to provide enhanced chemical and photo‐stability to ultra‐thin perovskites that support excitonic transitions and better photo‐responsivities. Here, we chemically synthesize ultra‐thin dual phase layered perovskites that remain room condition stable without any passivation layers and show a high responsivity of 9.51 A / W at 405 nm indicative of strong internal gain from subsequent trapped carrier excitations. In addition to strong exciton binding energies that provide higher overall responsivities, the ultra‐thin layers permit efficient gate control that lowers dark currents and provide two orders of magnitude improvement in the signal‐to‐noise ratio. These results make the room condition stable dual‐phase layered perovskites an attractive material for next generation sensitive and flexible photodetectors.