SCAPS-1D simulation of lead-free Cs₂TiBr₆ based perovskite solar cells: the impact of electron and hole transport layers

Perovskite solar cells (PSCs) have garnered significant attention due to their remarkable power conversion efficiency, yet concerns surrounding the stability and toxicity of lead halide perovskites have hindered their full-scale commercialization. In addressing this dilemma which arise in part from energy band misalignment, this study employs computational modeling to investigate Cs 2 TiBr 6 PSCs connected through various hole transport layers (HTLs) and electron transport layers (ETLs). Furthermore, a comprehensive investigation of parameters such as the absorber layer thickness, defect density, operating temperature, and rear metal electrode configuration has been conducted to optimize the photovoltaic performance. Through systematic optimization, a promising configuration comprising the layer sequence Glass/FTO/ZnO/Cs 2 TiBr 6 /CZTSe/Au has been identified, yielding a potential power conversion efficiency of 20.40%. Additionally, an alternative configuration, Glass/FTO/ZnO/Cs 2 TiBr 6 /CZTSe/Pt, has suggested a further enhancement in power conversion efficiency up to 30.37%. Notably, this configuration yields the highest V oc of 1.21 V, Jsc of 28.24 mA/cm², and FF of 89.12%, resulting in an impressive PCE of 30.61% when selenium (Se) is used instead of Platinum (Pt) as the back contact material. The exceptional performance of the CZTSe HTL is attributed to the quantum efficiency (QE) of the device, which indicates a proper alignment of its energy bands with those of the double perovskite absorber layer. This synergetic alignment is deemed responsible for improved efficiency.