Unveiling the Dynamic Processes in Hybrid Lead Bromide Perovskite Nanoparticle Thin Film Devices

Hybrid and all-inorganic perovskite (PK) materials are a promising next generation of semiconducting materials due to their outstanding light-harvesting features, as well as their color-tunablility and efficient luminescent properties that lead to highly efficient photovoltaic and lighting devices. Bulk PK films are both ionic and electronic conductors under the presence of an externally applied electric field. In this work, the internal ion motion behavior is demonstrated within PK nanoparticles in thin-film devices by means of different long-time poling scheme assays and both static and dynamic electrochemical impedance spectroscopy measurements. In particular, the existence of a dynamic device behavior is related to the migration and rearrangement of different ionic species upon applying different driving schemes. The latter resembles the well-known signatures of the ionic motion in light-emitting electrochemical cells (LECs), that is, (i) the formation of electrical double layers due to the ionic distribution at the electrodes' interfaces, (ii) the growth of the doped regions once the charge injection is effective, and (iii) the subsequent formation of a non-doped region in the bulk of the device. Hence, this comprehensive study opens up an alternative route toward understanding the dynamics inside hybrid perovskite materials based on the large body of knowledge of LECs.