Morphology‐Dependent Charge Carrier Dynamics and Ion Migration Behavior of CsPbBr₃ Halide Perovskite Quantum Dot Films

Abstract

Exceptional electronic, optoelectronic, and sensing properties of inorganic Cs‐based perovskites are significantly influenced by the defect chemistry of the material. Although organic halide perovskites that have a polycrystalline structure are heavily studied, understanding of the defect properties at the grain boundaries (GB) of inorganic Cs‐based perovskite quantum dots (QDs) is still limited. Here, morphology‐dependent charge carrier dynamics of CsPbBr3 quantum dots at the nanoscale by performing scanning probe microscopy of thermally treated samples are investigated. The grain boundaries of defect‐engineered samples show higher surface potential than the grain interiors under light illumination, suggesting an effective role of GBs as charge collection and transport channels. The lower density of crystallographic defects and lower trap density at GBs specifically of heat‐treated samples cause insignificant dark current, lower local current hysteresis, and higher photocurrent, than the control samples. It is also shown that the decay rate of surface photovoltage of the heated sample is quicker than the control sample, which implies a considerable impact of ion migration on the relaxation dynamic of photogenerated charge carriers. These findings reveal that the annealing process is an effective strategy to control not only the morphology but also the optoelectrical properties of GB defects, and the dynamic of ion migration. Understanding the origin of photoelectric activity in this material allows for designing and engineering optoelectronic QD devices with enhanced functionality.

CsPbI3 Perovskite Quantum Dot-Based WORM Memory Device with Intrinsic Ternary States

“…Based on these findings, we propose two pathways for the migration of V I s, namely, the grain boundary pathway and the grain interior pathway, to explain the ternary states observed in our RS devices, as summarized in Scheme . Initially, thermal annealing of the PQDs allows surface ligands to detach, which generates iodine vacancies that are preferentially located at GBs to form a few CFs, giving rise to iLRS (Scheme a). During the RESET process, the large current flowing through CF generates significant Joule heat, facilitating the lateral diffusion of iodine vacancies and CF annihilation, transitioning the device from iLRS to HRS (Scheme b).…”

Pyro-Phototronic Effect in All-Inorganic Two-Dimensional Ruddlesden–Popper Ferroelectric Perovskite Thin-films and Photodetection

“…It may be stated that, as obtained from XPS studies, the electronic arrangement of Pb 2+ is 5d 10 6s 2 6p 0 ; the (6s) 2 lone pair electron configuration of lead remains the driving force in distorting the octahedron. , Both the butterfly and hysteresis loops in the PFM studies could be seen to be shifted to the positive side of the applied voltage (Figure d,e). The imprint phenomena likely originate due to (i) the asymmetry in the trapped charge distribution and/or (ii) the alignment of defect dipoles near the electrode–sample interface. , …”

Influence of A-Site Composition on the Nanostructure and Electrical Properties of APbI3 Perovskite Films: Implications for Solar Cells

“…Extensive research has been dedicated to improving the efficiency and stability of PSCs by mitigating hysteresis. − Previous studies have revealed that GBs in perovskite films play a crucial role in ion migration pathways. , In order to investigate the influence of A-site doping on the GB regions, we utilized KPFM and C-AFM to measure the surface potential and current of the three thin films. The surface potential images of the three thin films under dark and illuminated conditions are depicted in Figure a–f.…”