Determination of complex optical constants and photovoltaic device design of all-inorganic CsPbBr₃ perovskite thin films

<jats:p>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<jats:sub>3</jats:sub>) thin films and determining their complex optical constants, which is a key requirement for photovoltaic device design. CsPbBr<jats:sub>3</jats:sub> 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 (<jats:italic toggle="yes">Ψ</jats:italic>) and delta (<jats:italic toggle="yes">Δ</jats:italic>). For the present model, bulk planar CsPbBr<jats:sub>3</jats:sub> 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<jats:sub>3</jats:sub> solar cells are conducted via the finite-difference time-domain method to investigate the properties of light absorption and photocurrent density.</jats:p>