Computational Design of Highly Efficient and Robust Hole Transport Layers in Perovskite Solar Cells

Abstract

We investigated the effects of materials and the film thickness of hole transport layers (HTLs) on inverted type perovskite solar cells using optics-charge transport coupled simulations. Power conversion efficiencies (PCEs), and the variations in efficiency induced by the film thickness dispersion, were intensively studied, to compare potential HTLs candidates like NiOx, PEDOT:PSS, CuSCN, and CuI. The optimum thickness of the solar cell layers differed based on the chosen combination of HTL and perovskite. It is suggested that the optoelectronic properties of HTLs like band gap, extinction coefficient, and refractive index can be used to determine the best ideal efficiencies, and sensitivity to process fluctuation. CuSCN showed the most promising behaviors, in that it can produce over-25% PCEs, and the lowest efficiency dispersion for various HTL thickness conditions. The best performance by CuSCN can be ascribed to its having a proper refractive index with the perovskite layer, and wide band gap characteristic. NiOx and CuI showed PCEs comparable to the CuSCN, but their efficiencies were sensitive to the varying thickness of the HTL. PEDOT:PSS exhibited the lowest simulated PCEs due to its small band gap. Our study suggests the best HTL candidates for inverted type perovskite solar cells, and demonstrates the importance of sophisticated numerical material studies, and device design, when developing highly efficient and robust perovskite solar cells. Key words: perovskite solar cells, hole transport layers, simulation, optimization, inverted type