Organic–inorganic mixed halide perovskites have emerged as an excellent class of materials with a unique combination of optoelectronic properties, suitable for a plethora of applications ranging from solar cells to light‐emitting diodes and photoelectrochemical devices. Recent works have showcased hybrid perovskites for electronic applications through improvements in materials design, processing, and device stability. Herein, a comprehensive up‐to‐date review is presented on hybrid perovskite electronics with a focus on transistors and memories. These applications are supported by the fundamental material properties of hybrid perovskite semiconductors such as tunable bandgap, ambipolar charge transport, reasonable mobility, defect characteristics, and solution processability, which are highlighted first. Then, recent progresses on perovskite‐based transistors are reviewed, covering aspects of fabrication process, patterning techniques, contact engineering, 2D versus 3D material selection, and device performance. Furthermore, applications of perovskites in nonvolatile memories and artificial synaptic devices are presented. The ambient instability of hybrid perovskites and the strategies to tackle this bottleneck are also discussed. Finally, an outlook and opportunities to develop perovskite‐based electronics as a competitive and feasible technology are highlighted.

Perovskite oxides such as PbZr x Ti 1-x O 3 (PZT) and BaTiO 3 show excellent dielectric, piezoelectric, pyroelectric and ferroelectric properties simultaneously and have been widely used in capacitor, sensor, actuator, motor, surface acoustic wave devices (SAW) and energy storage applications. Recently, a variety of solution-processed halide perovskite materials were discovered to exhibit fascinating properties such as high charge mobility, strong light absorption and even ferroelectricity. In this review, we summarize the recent progress on two classes of halide perovskite ferroelectrics. The first class is organo-lead halide perovskite semiconductor such as MAPbI 3 , which have been intensively pursued for solar cell and light emitting diode applications. Dynamic ferroelectric polarization is believed to be one of the This article is protected by copyright. All rights reserved. 2 essential factors to protect carriers from being scattered by charged defects in these halide perovskites. The second class is normal/multilayered halide perovskite ferroelectrics with large polarization or strong piezoelectricity. The piezoelectric coefficient of these latter perovskites can be as high as ~1540 pC N -1 , comparable to those of PZT-based ferroelectrics.Multiaxial polarizations and morphotropic phase boundaries (MPB) have also been demonstrated in such halide perovskites. Overall, the fast development of halide perovskite ferroelectrics opens a new venue for not only advancing fundamental materials science but also designing novel electronic and photoelectric devices.

Figure 1. (a) Schematic band diagram showing hydrogen and oxygen evolution with two different semiconductor photoelectrodes. Reproduced with permission. 24 Copyright 2019, Royal Society of Chemistry. The band energetics at a n-type semiconductor/electrolyte interface (b) after equilibration under dark conditions and (c) in quasi-static equilibrium under illumination, where H 2 O/O 2 and H 2 /H + represent electrolyte redox couples; V H represents the Helmholtz layer potential drop, ϕ s the semiconductor work function, and ϕ R the electrolyte work function; E F,n and E F,p represent the electron quasi-Fermi level and the hole quasi-Fermi level, respectively. (d) Band edge positions (vs NHE) and theoretical photocurrents under Air Mass 1.5 illumination for some commonly used semiconductors. Reproduced with permission. 31