Motivated by the exciting properties of metal halide perovskites in photovoltaic applications, there is an evolving need to further explore the limitations of this class of materials in broader fields and high end optoelectronics, which requires better control over the film structure, defect levels, and quality. Epitaxial growth has been ubiquitously deployed in the semiconducting industry. This affords routes to precisely align the atomic arrangement to control the structure and strain and achieve the highest levels of optoelectronic performance. In this review, the recent emergence and progress in the epitaxial growth of metal halide perovskites are introduced within the context of epitaxial and quasiepitaxial approaches, and recent advances are surveyed from growth methods to application integration. The main criteria distinguishing epitaxy and quasiepitaxy, i.e., lattice matching and ordering, can be deployed to direct the selection of proper substrates, growth methods, and precursors for various applications.

A full range of optoelectronic devices has been demonstrated incorporating hybrid organic–inorganic halide perovskites including high-performance photovoltaics, light emitting diodes, and lasers. Tin-based inorganic halide perovskites, such as CsSnX3 (X = Cl, Br, I), have been studied as promising candidates that avoid toxic lead halide compositions. One of the main obstacles for improving the properties of all-inorganic perovskites and transitioning their use to high-end electronic applications is obtaining crystalline thin films with minimal crystal defects, despite their reputation for defect tolerance in photovoltaic applications. In this study, the single-domain epitaxial growth of cesium tin iodide (CsSnI3) on closely lattice matched single-crystal potassium chloride (KCl) substrates is demonstrated. Using in situ real-time diffraction techniques, we find a new epitaxially-stabilized tetragonal phase at room temperature that expands the possibility for controlling electronic properties. We also exploit controllable epitaxy to grow multilayer two-dimensional quantum wells and demonstrate epitaxial films in a lateral photodetector architecture. This work provides insight into the phase control during halide perovskite epitaxy and expands the selection of epitaxially accessible materials from this exciting class of compounds.

Summary Inorganic halide perovskites have emerged as a promising platform in a wide range of applications from solar energy harvesting to computing and light emission. The recent advent of epitaxial thin film growth of halide perovskites has made it possible to investigate low-dimensional quantum electronic devices based on this class of materials. This study leverages advances in vapor-phase epitaxy of halide perovskites to perform low-temperature magnetotransport measurements on single-domain cesium tin iodide (CsSnI 3 ) epitaxial thin films. The low-field magnetoresistance carries signatures of coherent quantum interference effects and spin-orbit coupling. These weak anti-localization measurements reveal a micron-scale low-temperature phase coherence length for charge carriers in this system. The results indicate that epitaxial halide perovskite heterostructures are a promising platform for investigating long coherent quantum electronic effects and potential applications in spintronics and spin-orbitronics.

High-quality single-crystal inorganic halide perovskites have begun to attract interest for future quantum devices applications. In this work, we focus on the quantum transport properties of single-crystal epitaxial halide perovskites and present low-temperature quantum magnetotransport measurements on thin film devices of single-crystal cesium tin bromide (CsSnBr3) at low temperature. We demonstrate that the system exhibits two-dimensional (2D) Mott variable range hopping (VRH) transport with a giant negative magnetoresistance. This large negative magnetoresistance can be described by the Nguyen-Spivak-Shkovskii (NSS) model which describes the quantum interference of different directed hopping paths of charge carriers. Based on this model, we extract the temperature-dependent hopping length of charge carriers in epitaxial CsSnBr3, estimate their localization length, and find a lower bound for their phase coherence length of ~ 100 nm at low temperatures. These new observations add to a growing body of experimental evidence that demonstrate that epitaxial halide perovskites are emerging as a new material class for the study of lowdimensional quantum coherent transport phenomena.

Covering greenhouses and agricultural fields with photovoltaics has the potential to create multipurpose agricultural systems that generate revenue through conventional crop production as well as sustainable electrical energy. In this work, we evaluate the effects of wavelength-selective cutoffs of visible and near-infrared (biologically active) radiation using transparent photovoltaic (TPV) absorbers on the growth of three diverse, representative, and economically important crops: petunia, basil, and tomato. Despite the differences in TPV harvester absorption spectra, photon transmission of photosynthetically active radiation (PAR; 400–700 nm) is the most dominant predictor of crop yield and quality. This indicates that different wavebands of blue, red, and green are essentially equally important to these plants. When the average photosynthetic daily light integral is > 12 mol m–2 d–1, basil and petunia yield and quality is acceptable for commercial production. However, even modest decreases in TPV transmission of PAR reduces tomato growth and fruit yield. These results identify crop-specific design requirements that exist for TPV harvester transmission and the necessity to maximize transmission of PAR to create the most broadly applicable TPV greenhouse harvesters for diverse crops and geographic locations. We determine that the deployment of 10% power conversion efficiency (PCE) plant-optimized TPVs over approximately 10% of total agricultural and pasture land in the U.S. would generate 7 TW, nearly double the entire energy demand of the U.S.