Vacuum deposition of CsPbI 3 layers on textured Si for Perovskite/Si tandem solar cells

We attempt the conformal deposition of CsPbI 3 layers on pyramidal-shaped textured crystalline Si (c-Si) surfaces, aiming at application to Perovskite/Si tandem solar cells. CsPbI 3 layers are deposited through vacuum evaporation on textured c-Si surfaces with various pyramid sizes. Conformal CsPbI 3 layers are formed on the textured c-Si, which is, in principle, difficult to be realized by conventional solution processes. We also confirmed a reduction in the optical reflectance of CsPbI 3 /Si structures by ∼10% (absolute) by using textured c-Si compared to the case of flat Si. A co-evaporation method can prevent the aggregation of CsI particles, which are seen when the films are formed by sequential evaporation. These results indicate the feasibility of Perovskite/c-Si tandem cells with textured c-Si, leading to low optical reflectivity and a high photocurrent.