Structural and Optical Properties of Vacuum‐Evaporated Mixed‐Halide Perovskite Layers on Nanotextured Black Silicon

To improve the absorption of light in two‐junction tandem perovskite–silicon solar cells, antireflective textures are often created on the front surface in the form of micronsized pyramids using wet‐chemical etching. It is known that single‐junction silicon solar cells with nanotextured black silicon (BS) formed by dry‐etching techniques are more efficient than pyramidal microtextures. Herein, experimental evidence of enhanced efficiency of structures using BS between the perovskite layer and the silicon substrate for the first time is demonstrated. BS is fabricated using plasma‐based reactive‐ion etching on the front surface of the crystalline silicon. The deposition of mixed‐halide perovskite layers is performed by vacuum coevaporation and sequential evaporation. The structural and optical properties of evaporated perovskite layers with various thicknesses are investigated. It is found that the structural‐phase quality (viz., surface coverage, chemical composition, dimensionality, crystallinity, and phase purity) of perovskite layers on planar and nanotextured substrates is similar. However, the root mean square roughness of the perovskite layers on nanotextured substrates is much higher, which reduces the reflection significantly, especially, in the range of radiation incidence angle up to 60°. These results pave the way for the development of high‐performance perovskite–silicon tandem solar cells for improved efficiency. The structural and optical properties of mixed‐halide perovskite layers deposited on black silicon (BS) by vacuum evaporation are investigated. A significant reduction in the reflection of perovskite layers is demonstrated. This is achieved without compromising the structural quality of the perovskite layer as a photoabsorber. The results confirm the promise of using BS for perovskite–silicon tandem junction solar cells.