Optimization of Cs ₂ SnBr ₆ /Cs ₂ TeI ₆ bilayer absorber for enhanced performance in perovskite solar cell

Abstract This study presents a novel multi-absorber-layer perovskite solar cell (PSC) design addressing single-layer absorber limitations by integrating Cs 2 SnBr 6 and Cs 2 TeI 6 . These materials were chosen for their complementary absorption properties, with Cs 2 SnBr 6 covering the UV-visible range and Cs 2 TeI 6 capturing light in the visible spectrum, ensuring broad-spectrum absorption. The device is meticulously configured with PCBM ([6,6]-Phenyl-C61-butyric acid methyl ester) as the electron transport layer and Cu 2 O as the hole transport layer, selected for their exceptional carrier mobility and compatibility with the absorbers based on conduction and valence band alignment. The transparent front contact comprises indium tin oxide (ITO) to ensure optimal light transmission and effective charge collection, while the back contact is made of Au for its superior conductivity and stability. Under optimized conditions, the solar cell (ITO/PCBM/Cs 2 SnBr 6 /Cs 2 TeI 6 /Cu 2 O/Au) demonstrates remarkable performance metrics, including a short-circuit current density of 33.32 mA.cm −2 , an open-circuit voltage of 1.29 V, fill factor of 90.07%, and power conversion efficiency of 38.62%. Furthermore, a machine learning-based analysis was employed to study the effect of relative humidity, on device performance. The ML model helps identify degradation trends and predict stability under varying environmental conditions, supporting the development of more robust and moisture-resistant PSCs.