EXPLORING HYSTERESIS IN CURRENT-VOLTAGE CHARACTERISTICS OF HALIDE PEROVSKITES: MECHANISMS AND IMPLICATIONS

Abstract

Hybrid halide perovskites have garnered significant interest for optoelectronic devices due to their remarkable optical properties and cost-effective synthesis. However, their full potential remains limited by an incomplete understanding of their electrical behavior. This thesis investigates the impact of grain structure on hysteresis in CsPbBr3 perovskite materials. Current-voltage characteristics are analyzed for single-grain nanocrystals (SG-NCs), multigrain nanocrystals (MG NCs), and polycrystalline thin films (PTFs) under varying scan rates and illumination. The results demonstrate extensive hysteresis across a broad voltage range in PTFs, attributed to grain boundaries facilitating ion migration. Conversely, SG-NCs exhibit minimal hysteresis limited to a narrow voltage window, suggesting polarization and ion confinement within the nanocrystals. Interestingly, MG-NCs display a combination of long- and short-range hysteresis due to the presence of internal grain boundaries while maintaining some degree of ion confinement. These findings establish a clear correlation between grain boundaries and hysteresis behavior, providing valuable insights into charge transport mechanisms within perovskite materials. Building upon the understanding of hysteresis, this thesis also delves into the switching mechanism of halide perovskite memristors, aiming to exploit their hysteresis for information storage and brain-inspired computing, by exploring the current-voltage characteristics and impedance spectroscopy of ITO/MAPbBr3/Au devices to analyze the SET-RESET states under varying light intensities and applied biases. The results suggest a clear correlation between increased light power and a shift in the SET voltage, indicating the involvement of electronic-ionic coupling and light-induced ion migration. Additionally, impedance spectroscopy reveals a negative slope in the AC conductivity at the SET state, particularly at low frequencies. This phenomenon is attributed to the presence of an ion-induced voltage that gets progressively screened by photogenerated charge carriers under illumination. These findings provide valuable insights into the switching mechanism of perovskite memristors, paving the way for their development as high-performance memory devices for neuromorphic computing applications.