Elucidating the Role of Ion Migration and Band Bending in Perovskite Solar Cell Function at Grain Boundaries via Multimodal Nanoscale Mapping

Abstract

Although hybrid organic–inorganic halide perovskite solar cells have achieved extraordinary improvements over the past few years, questions remain about the role of grain boundaries. This article reports on the nanoscale point‐by‐point current–voltage mapping of photovoltaic characteristics in inverted methylammonium lead triiodide perovskite solar cells. These measurements reveal an increased open‐circuit voltage and shunt resistance, along with a suppressed short‐circuit photocurrent at grain boundaries and nearby regions. Support from nanoscale ionic strain and surface potential mapping suggests that local ion accumulation and downward band bending can facilitate charge separation, but hinder charge collection at grain boundaries.

Observation of Grain Boundary Passivation and Charge Distribution in Perovskite Films Improved with Anti-solvent Treatment

“…It is clear from the images that the GBs had a negative potential as compared to the GIs corresponding to downward band bending, which indicates a higher surface photovoltage and higher current collection than in GIs. 29,39,40 GBs are ascribed to vacancies and considered beneficial for electron hole pair separation and collection. 29 From the histograms (Figure S5), it is clear that the overall potential of the perovskite layer decreased after the hot CB treatment and the GB/GI potential difference also decreased.…”

Recent Advances in CsPbX3 Perovskite Solar Cells: Focus on Crystallization Characteristics and Controlling Strategies

“…Extended Defects: Due to the chemical instability of perovskite materials, the production of some electron defects is likely on the surface or GBs of perovskite crystals, such as uncoordinated halide ions and uncoordinated Pb 2+ , as shown in Figure 3c. [73] The migration of those charged defects under an electric field can lead to the accumulation of charged ions at the interface, resulting in unfavorable band bending, [74,75] interfacial reactions, and phase separation, [28] thus affecting carrier extraction and transport, causing current density-voltage (J-V) hysteresis and device degradation. [76] These uncoordinated sites are prone to reduction or oxidation reactions under the external environment, light, heat, and humidity.…”

Epitaxial Growth of Quasi-intrinsic CsPbBr3 Film on a SrTiO3 Substrate by Pulsed Laser Deposition

“…Recently, the application of hybrid halide perovskite semiconductor materials in high-performance solar cells, , X-ray detection, , and other thin film electronics has been a research hotspot. , A photovoltaic conversion efficiency of a solar cell over 25% has been achieved with solution-processed polycrystalline perovskite thin films, which have high defect density in the photoactive layer . Several reports demonstrated that the electronic device performance mainly depends on the film quality, such as the substrate/film interface, and grain boundaries of polycrystalline films are the main sites for free charge nonradiative recombination. , Meanwhile, single-crystal halide perovskite thin films have better photoelectric performance than the polycrystalline counterparts; , for example, grain-boundary-free single-crystal thin films have higher carrier mobility and lower trap density. − Hence, the growth of high-quality thin film is of great significance to the physical research and device applications of halide perovskites.…”

“…Recently, the application of hybrid halide perovskite semiconductor materials in high-performance solar cells, 6,7 Xray detection, 8,9 and other thin film electronics has been a research hotspot. 10,11 A photovoltaic conversion efficiency of a solar cell over 25% has been achieved with solution-processed polycrystalline perovskite thin films, which have high defect density in the photoactive layer.…”