Perovskite Single‐Crystal Solar Cells: Advances and Challenges

In just over a decade, the power conversion efficiency of metal-halide perovskite solar cells has increased from 3.9% to 25.5%, suggesting this technology might be ready for large-scale exploitation in industrial applications. Photovoltaic devices based on perovskite single crystals are emerging as a viable alternative to polycrystalline materials. Perovskite single crystals indeed possess lower trap state densities, higher carrier mobilities, and longer diffusion lengths, and potentially can achieve higher performance with respect to those fabricated with polycrystalline films, although their integration in a complete device needs particular attention and the use of specifically tailored growth techniques. In this review, recent advances on single-crystal halide perovskites are reported. First, crystalline structure and fundamental properties of 3D perovskites are discussed, including the emerging mixed-anion cation perovskites, and then the most popular growth methods with a focus on techniques that enable the implementation in photovoltaic devices are presented. Architectures and materials used to produce lateral and vertical solar cells are further introduced and recent improvements in device design and fabrication are summarized. Finally, the strategies used to solve the still open challenge on these materials regarding stability under environmental conditions are critically discussed and the view on the opportunities offered by halide perovskites is reflected.