Memristive devices such as resistive switching memories and artificial synapses have emerged as promising technologies to overcome the technological challenges associated with the von Neumann bottleneck. Recently, lead halide perovskites have drawn substantial research attention as the candidate material for memristors and artificial synapses due to their unique optoelectronic properties, solution processability, and mechanical flexibility. However, the toxicity of lead‐containing species has raised major concerns for health and the environment, which makes it crucial to transition from lead‐based to lead‐free materials for practical applications. Herein, the recent progress of lead‐free metal halides including perovskites and perovskite analogs for resistive memory and artificial synapse is reviewed. Initially, the fundamentals of lead‐free materials and switching mechanisms are introduced. Next, the material design, fabrication technique, and device performance are summarized and critically evaluated for each metal halide species. Finally, the challenges of the lead‐free metal halides toward memristors and artificial synapses are outlined and discussed, and some potential research directions for future study are proposed.

Bismuth-based organohalides have attracted much attention as potential alternatives to lead halide perovskites and have been explored in various electronic and optoelectronic devices. Developing new bismuth organohalides with rational design has been a dynamic research area. Herein, we developed single-crystals and thin-films of a new class of bismuth-based organohalides (phenethylammonium (C₈H₁₂N⁺, PEA⁺) bismuth halides). We found that comparable optical properties can be preserved after replacing methylammonium with bulky PEA⁺ cations. The bulky PEA⁺ cation significantly promotes the coverage and low surface roughness of bismuth organohalide thin-films in a facile one-step solution method. Newly-prepared (PEA)₃Bi₂I₉ also shows excellent thermal and humidity stability, showing promise for addressing the toxicity and stability of optoelectronic/electronic devices beyond lead halide perovskites.

The facile oxidation of Sn²⁺ to Sn⁴⁺ poses an inherent challenge that limits the efficiency and stability of tin‐lead mixed (Sn−Pb) perovskite solar cells (PSCs) and all‐perovskite tandem devices. In this work, we discover the sustainable redox reactions enabling self‐healing Sn−Pb perovskites, where their intractable oxidation degradation can be recovered to their original state under light soaking. Quantitative and operando spectroscopies are used to investigate the redox chemistry, revealing that metallic Pb⁰ from the photolysis of perovskite reacts with Sn⁴⁺ to regenerate Pb²⁺ and Sn²⁺ spontaneously. Given the sluggish redox reaction kinetics, V³⁺/V²⁺ ionic pair is designed as an effective redox shuttle to accelerate the recovery of Sn−Pb perovskites from oxidation. The target Sn−Pb PSCs enabled by V³⁺/V²⁺ ionic pair deliver an improved power conversion efficiency (PCE) of 21.22 % and excellent device lifespan, retaining nearly 90 % of its initial PCE after maximum power point tracking under light for 1,000 hours.

Metal halide perovskites emerge as promising semiconductors for optoelectronic devices due to ease of fabrication, attractive photophysical properties, their low cost, highly tunable material properties, and high performance. High‐quality thin films of metal halide perovskites are the basis of most of these applications including solar cells, light‐emitting diodes, photodetectors, and electronic memristors. A typical fabrication method for perovskite thin films is the solution method, which has several limitations in device reproducibility, adverse environmental impact, and utilization of raw materials. Thermal evaporation holds great promise in addressing these bottlenecks in fabricating high‐quality halide perovskite thin films. It also has high compatibility with mass‐production platforms that are well‐established in industries. This review first introduces the basics of the thermal evaporation method with a particular focus on the critical parameters influencing the thin film deposition. The research progress of the fabrication of metal halide perovskite thin films is further summarized by different thermal evaporation approaches and their applications in solar cells and other optoelectronic devices. Finally, research challenges and future opportunities for both fundamental research and commercialization are discussed.