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.
Hybrid organic–inorganic halide perovskite solar
cells (PSCs)
have garnered significant attention in the field of photovoltaics.
Despite the rapid advancements in photoelectric conversion efficiency
(PCE), the sensitivity of hybrid perovskites to moisture and heat
poses challenges to device stability. All-inorganic PSCs (AIPSCs)
eliminate the use of traditional organic components, resulting in
significantly extended operational lifetimes. Herein, we report the
doping of indium bromide (InBr3) into the lattice of CsPbI2.5Br0.5-based all-inorganic perovskites, leading
to large crystalline grain sizes and tunable energy band levels by
adjusting the concentration of InBr3 dopants. AIPSCs based
on highly stable In-doped CsPbI2.5Br0.5 absorber
layers can be conveniently fabricated in an ambient air environment.
Moreover, screen-printable nanocarbon counter electrodes with high
stability and low cost are introduced to replace unstable organic
hole-transport materials and expensive noble metal electrodes, thus
further increasing ambient stability and greatly reducing device costs.
As a result, the In-doped CsPbI2.5Br0.5-based
AIPSCs achieve a champion PCE of 12.05% and favorable heat endurance
with a PCE retention of 80% after being continuously heated at 100
°C for over 1632 h. This work provides a feasible strategy of
lattice doping to tackle the intractable issue regarding the intrinsic
thermal instability of inorganic perovskite materials for fabricating
AIPSCs with a wide absorption range and high environmental stability.
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