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 (CsPbBr3) thin films and determining their complex optical constants, which is a key requirement for photovoltaic device design. CsPbBr3 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 CsPbBr3 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 CsPbBr3 solar cells are conducted via the finite-difference time-domain method to investigate the properties of light absorption and photocurrent density.
Highlights
Since the first perovskite solar cell (PSC) was reported in 2009 [1], a massive research effort has been underway
CsPbBr3 thin film is deposited on the rear of fluorine-doped tin oxide (FTO) thin film coated glass substrates and as a result, the sample structure consists of CsPbBr3 thin film/glass substrate/FTO thin film
The measured X-ray diffraction (XRD) pattern of the as-prepared CsPbBr3 thin film on the bare glass substrate is shown in Fig. 1(a), where the inset is a photo of the sample and a standard XRD pattern of a cubic CsPbBr3 is cited from Ref. [25]
Summary
Since the first perovskite solar cell (PSC) was reported in 2009 [1], a massive research effort has been underway. The power conversion efficiency (PCE) of the organic-inorganic hybrid PSCs based on lead halides progressed rapidly from 3.8% to a certificated record efficiency of 24.2% [1,2]. A key challenge confronting PSCs is their poor stability against humidity, heat, and UV light, which is delaying their appearance in the marketplace [3]. All-inorganic cesium lead bromide (CsPbBr3) PSCs have attracted significant attention due to their greatly improved stability [4,5,6]. Several groups have demonstrated excellent stability of CsPbBr3 PSCs against humidity and heat when compared with conventional organicinorganic hybrid PSCs [7,8,9]. Optical simulations are definitely helpful to physical understandings on light interaction with the material, and for investigating different solar cell architectures
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