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Hybrid perovskites have attracted great interest in solar energy conversion and optoelectronic applications. The interconnected ionic and electronic effects complicate assessing the underlying electrical processes while contributing greatly to the efficiency and stability of devices. Fortunately, these coupled processes manifest on distinct timescales that enable frequency-specific electrochemical analysis. However, hybrid perovskites dissolve in most of the common aqueous and organic solvents utilized for electrochemistry. Here, we utilize a hydrofluoroether (HFE) solvent toolkit to perform nondestructive electrochemical impedance spectroscopy of methylammonium lead iodide (MAPbI3) perovskite thin films. This enables the extraction of dielectric constants and double-layer formation in these perovskite films. 

A Reset MOSFET is added to a perovskite MOSFET-based photodetector to serve as a current source to mitigate the influence of ionic movement on the performance of the photodetector. With the added MOSFET, the hysteresis is significantly reduced, and the dark current is controllable. The on/off ratio resumes to 10^6 and an ultrasensitive responsivity (over 80,000 A/W) is achieved under only 13 nW/cm^2 red (665 nm) light intensity. 

Perovskites have emerged as a forerunner of electronics research due to their vast potential for optoelectronic applications. The numerous combinations of constituent ions and the potential for doping of perovskites lead to a high demand to track the underlying electronic properties. Solution‐based electrochemistry is particularly promising for detailed and facile assessment of perovskites. Here, electrochemical impedance spectroscopy (EIS) of methylammonium lead iodide (MAPbI₃) thin films is performed and model them with an equivalent circuit that accounts for solvent, ionic, and thin film effects. A dielectric constant consistent with prior AC studies and a diffusion constant harmonious with cation motion in MAPbI₃are extracted. An electrical double layer thickness in the perovskite film of 54 nm is obtained, consistent with lithium doping in perovskite films. Comparing the EIS and equivalent circuit model of perovskite films to control ITO‐only data enabled the assignment of the ions at each interface. This comparison implied a double layer of primarily lithium ions inside the perovskite film at the solution interface with significant recombination of ions on the solution side of the interface. This demonstrates EIS as a powerful tool for studying the fundamental charge accumulation and transport processes in perovskite thin films.

 

Solution‐processed organic–inorganic metal halide perovskites have recently attracted tremendous attention in the photodetector community due to their excellent optoelectronic properties and facile fabrication. The main challenge in perovskite photodetectors (PSPDs) is to achieve high responsivity and fast speed simultaneously. In this work, this challenge is overcome by employing a directly patterned nanograting methylammonium lead iodide (MAPbI₃) film in metal‐semiconductor‐metal (MSM) PSPD on interdigitated indium tin oxide (ITO) electrodes. Because of the improved perovskite morphology after directly patterning by nanoimprint lithography, as well as the enhanced electric field intensity by the perovskite nanograting and interdigitated electrodes, the PSPDs have responsivity of 441 A W⁻¹, detectivity of 8.32 × 10¹²Jones, response time of 10.7 µs, all of which are among the best performances in MSM PSPDs. Moreover, the PSPDs maintain excellent photocurrent performance after 20 days of air exposure. The approach opens a path to manufacturing‐friendly, high‐performance, and reliable PSPDs and paves the way toward perovskite‐based optoelectronic circuits.