Dual-layer perovskite architectures for improved all-inorganic photovoltaic performance

Abstract

This study employs a one-dimensional solar cell capacitance simulator (SCAPS-1D) to investigate all-inorganic perovskite solar cells (PSCs) featuring single and bilayer absorbers, along with various electron transport layers (ETLs). We compared two devices, including a cesium lead triiodide (CsPbI₃) single absorber and CsPbI₃/cesium lead tribromide (CsPbBr₃) dual absorber. The bilayer absorber increases short-circuit current density (J_SC), open-circuit voltage (V_OC), fill factor (FF), and power conversion efficiency (PCE) to 19.48 mA cm⁻², 1.17 V, 79.4%, and 18.1%, respectively. This is because the energy bands are better aligned, the built-in potential is stronger, and the light absorption is higher. The optimization of absorber layer thickness reveals that 300 nm is optimum for CsPbI₃ and 700 nm thickness is the best for CsPbBr₃. Higher defect densities make all metrics degrade by increasing non-radiative recombination. Moreover, multiple ETLs were applied to further enhance and compare the photovoltaic (PV) performance of dual PSCs. Among all, strontium titanate (SrTiO₃) showed the highest PCE of 23.09% with a J_SC of 19.45 mA cm⁻², a V_OC of 1.36 V, and a FF of 87.06%. The obtained results confirm that the bilayer of CsPbI₃ and CsPbBr₃ synergistically enhances light absorption, band alignment, and carrier dynamics in PSCs.