Analysis of short-circuit current suppression mediated by strategically optimized buffer layer thickness in heterojunction solar cells

Abstract

The ever-growing global energy crisis and alarming environmental degradation have intensified the search for sustainable energy alternatives, with solar technology standing at the forefront of this revolution. Among cutting-edge photovoltaic (PV) advancements, heterojunction lead-free perovskite solar cells offer remarkable efficiency and environmental compatibility. This study presents a novel TiO₂/SnS/BiFeO₃/spiro-OMeTAD configuration, analysed through COMSOL simulations in 1D to optimize performance. The results demonstrate a maximum efficiency of 23.59% at 1 × 10¹⁹ cm⁻³ donor–acceptor (DA) density, confirming the potential of this structure for high-performance applications. Furthermore, the fill factor peaks at 82.94% near 150 nm electron transport thickness, highlighting enhanced charge collection. The open-circuit voltage reaches a maximum of 1.057 V at an SnS layer thickness of 10 nm and decreases with further thickness increase, attributed to the impact on energy band alignment. The short-circuit current is suppressed as the SnS layer's thickness increases, attributed to the impact on the layer's resistance. Conversely, the short-circuit current density attained a peak of 35.330 mA cm⁻² at a DA density of 1 × 10¹⁶ cm⁻³, due to improved charge carrier concentration at lower densities. These findings establish the feasibility of this heterojunction solar cell structure, providing a strong foundation for future experimental validation and optimization. This research paves the way for the development of next-generation, high-efficiency, and lead-free PV devices, promoting sustainable energy solutions.