Sensing and Ionovoltaic Power Generation of Two-Dimensional Cs₃Sb₂X₉ (X = Cl/Br/I) Perovskite Microcrystals

Energy conversion technologies have been developed in response to the depletion of fossil fuels and the increasing need for electricity in our daily lives. Our study presents pioneering research on the ionovoltaic effect in 2-dimensional (2D) lead-free perovskite lateral electrode structures separated by millimeter distances. This effect harnesses moisture adsorption to generate electricity. We have achieved results by leveraging the ionic properties of Cs₃Sb₂X₉ (X = Cl/Br/I) and utilizing a micrometer-thick perovskite film. For instance, Cs₃Sb₂Br₉ demonstrates an open-circuit voltage (V_oc) of 0.23 V and a corresponding short-circuit current (I_sc) of 2 μA at 85% relative humidity (RH). Our combined experimental and theoretical investigations highlight the role of water molecules in interacting with the perovskite layers, facilitating electricity generation by establishing a self-sustaining moisture gradient and ion gradient. The 2D perovskite structure maintains its crystal structure even after exposure to humidity for 30 days. Through density functional theory (DFT) analysis, we have examined the structural, electronic, and optical properties of Cs₃Sb₂X₉ (X = Cl/Br/I), observing a trend where band energy gaps decrease and absorption edges shift toward longer wavelengths as X varies from Cl to I. Additionally, we introduce breath-monitoring devices based on Cs₃Sb₂X₉ (X = Cl/Br/I). Cs₃Sb₂Br₉ exhibits a response and recovery duration of approximately 0.28 and 14.3 s, respectively, showcasing its potential for real-time breath analysis applications.