Properties of Vacuum-Evaporated Metal Halide Perovskite Absorbers on Planar and Nanotextured Silicon Substrates

The optical and structural properties of metal halide perovskite layers as absorbers for top solar cells in tandem applications were studied. CH3NH3PbI3−xClx perovskite layers were deposited on planar Si and glass substrates and nanotextured Si substrates by vacuum co-evaporation and sequential evaporation methods. Methylammonium chloride (CH3NH3Cl) and lead iodide (PbI2) were used as the raw precursors. Nanotexturing of the Si substrates was carried out using reactive ion etching in black Si formation mode. The experimental results show that sequentially evaporated (after annealing at 100 °C for 30 min) and co-evaporated layers had practically identical structural-phase quality and transmission spectra. The obtained perovskite layers were dense, without pores or cracks, and were formed by spherical-like crystallites. In the case of a nanotextured substrate, perovskite crystallites filled the interneedle spaces of the black Si layer. It was found that the black Si interlayer leads to a significant increase in the root mean square roughness of the perovskite layers and reduces the reflection of tandem structures.