Analysis and design of 25.3% efficient Sb2Se3 solar cells by numerical simulation

Sb₂Se₃ has a high absorption coefficient of 10⁵ cm⁻¹ in the visible light range, which is an excellent absorber layer material. Currently, a better band alignment between conventional CdS and Sb₂Se₃ has led to the widespread adoption of CdS as the electron transport layer (ETL) in Sb₂Se₃ solar cells. However, CdS is toxic, necessitating the exploration of alternative ETL materials that are eco-friendly and possess an appropriate energy band with Sb₂Se₃. In this study, we endeavor to pioneer an all-inorganic, green solar cell structure of Au/MoS₂/Sb₂Se₃/WS₂/ITO by employing MoS₂ as the hole transport layer (HTL) and WS₂ as the ETL. We primarily optimized Sb₂Se₃ thickness and its hole doping concentration (N_A) by SCAPS-1D numerical simulation. Based on the analysis of built-in electric field and carrier recombination rate along Sb₂Se₃, the optimal thickness and N_A ranges of Sb₂Se₃ are determined, which are 0.9–1.1 μm and 10¹⁶-10¹⁸ cm⁻³ respectively. Through a series of optimization, the structure achieves the highest power conversion efficiency (PCE) of about 25.3 % in the current simulation of Sb₂Se₃ solar cells. After comparing the novel WS₂ ETL with the conventional CdS ETL, we find that WS₂ has a larger built-in potential (V_bi) and charge recombination resistance (R_rec). In addition, from the analysis of energy band structure, the spike-like band at Sb₂Se₃/WS₂ interface can effectively inhibit the carrier recombination, which makes the device obtain a larger open circuit voltage (V_OC) of 0.69 V. This study can provide theoretical reference for the development of non-toxic and efficient Sb₂Se₃ solar cells.