Determination of complex optical constants and photovoltaic device design of all-inorganic CsPbBr<sub>3</sub> perovskite thin films
Wensheng Yan, Lingyun Mao, Peiyang Zhao, Adrian Mertens, Stephan Dottermusch, Hang Hu, Zhong Jin, Bryce S. Richards
Abstract
All-inorganic perovskites exhibit interesting properties and unprecedented stability compared to organic-inorganic hybrid lead halide perovskites. This work focuses on depositing and characterizing cesium lead bromide (CsPbBr 3 ) thin films and determining their complex optical constants, which is a key requirement for photovoltaic device design. CsPbBr 3 thin films are synthesized via the solution method followed by a hot-embossing step to reduce surface roughness. Variable angle spectroscopic ellipsometry measurements are then conducted at three angles (45°, 55°, and 65°) to obtain the ellipsometric parameters psi ( Ψ ) and delta ( Δ ). For the present model, bulk planar CsPbBr 3 layer is described by a one-dimensional graded index model combined with the mixture of one Tauc-Lorentz oscillator and two Gaussian oscillators, while an effective medium approximation with 50% air void is adopted to describe surface roughness layer. The experimental complex optical constants are finally determined in the wavelength range of 300 to 1100 nm. Furthermore, as a design example demonstration, the simulations of single-junction CsPbBr 3 solar cells are conducted via the finite-difference time-domain method to investigate the properties of light absorption and photocurrent density.