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

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 (∆). 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.

: Strong bidentate coordination for surface passivation and ligand-shell engineering of lead halide perovskite nanocrystals in the strongly quantum confined regime

“…, when considering the dielectric screening effect of the radiating field inside the nanoparticles, [64][65] where is the optical dielectric constants of solvents and ≈ 4 for CsPbBr3 in the pertained spectral window. 66 Our measurements of the passivated sample show a good linear relationship when plotted against the dielectric factors (Figure 3B), suggesting that exciton lifetimes in the passivated PNC proximate the radiative limit of PNCs. These lifetimes are indeed very close to the reported lifetimes of PNCs with near-unity PLQY [47][48] , implying that after PIC passivation, PNCs in the "bright" subensemble are nearly trap-free.…”

Strong bidentate coordination for surface passivation and ligand-shell engineering of lead halide perovskite nanocrystals in the strongly quantum confined regime

“…, when considering the dielectric screening effect of the radiating field inside the nanoparticles, [65][66] where is the optical dielectric constants of solvents and ≈ 4 for CsPbBr3 in the pertained spectral window. 67 Our measurements of the passivated sample show a good linear relationship when plotted against the dielectric factors (Figure 3B), suggesting that exciton lifetimes in the passivated PNC proximate the radiative limit of PNCs. These lifetimes are indeed very close to the reported lifetimes of PNCs with near-unity PLQY [47][48] , implying that after PIC passivation, PNCs in the "bright" subensemble are nearly trap-free.…”

Strong bidentate coordination for surface passivation and ligand-shell engineering of lead halide perovskite nanocrystals in the strongly quantum confined regime

“…, when considering the dielectric screening effect of the radiating field inside the nanoparticles, [65][66] where 𝜀 𝑠 is the optical dielectric constants of solvents and 𝜀 ≈ 4 for CsPbBr3 in the pertained spectral window. 67 Our measurements of the passivated sample show a good linear relationship when plotted against the dielectric factors (Figure 3B), suggesting that exciton lifetimes in the passivated PNC proximate the radiative limit of PNCs. These lifetimes are indeed very close to the reported lifetimes of PNCs with near-unity PLQY [47][48] , implying that after PIC passivation, PNCs in the "bright" subensemble are nearly trap-free.…”