HTL-Free 2D/3D Hybrid Perovskite Solar Cells: ETL Engineering and Simulation Insights

Abstract

The commercialization of PSCs is hindered by instability under heat, moisture, and UV, which is mitigated by 2D/3D hybrids that combine the stability of 2D and the efficiency of 3D perovskites. Despite improvements in intrinsic material stability, conventional device architectures using hole transport layers (HTLs) still face challenges in long-term durability. In this study, we numerically investigate HTL-free carbon electrode-based 2D/3D hybrid PSCs, focusing on optimizing the 3D perovskite layer properties and evaluating different electron transport layer (ETL) materials. Devices using TiO₂, SnO₂, WS₂, and C60 as ETLs achieved maximum PCEs of 19.15%, 20.25%, 20.00%, and 22.26%, respectively, at optimal 3D layer thicknesses of 0.9 μm, 1.3 μm, 1.4 μm, and 1.2 μm, respectively. The performance of all devices was maximized at a bulk defect density of 1012 cm-3. The results reveal that ETL has a significant impact on device performance in HTL-free 2D/3D hybrid PSCs. The study also highlights the critical role of the electrode work function, identifying 5.4 eV as the minimum threshold for efficient charge extraction in HTL-free 2D/3D hybrid PSCs.