Optimizing lead-free Cs₃Bi₂I₉ perovskite solar cells: exploring absorber and charge transport layers parameters for improved efficiency

Lead-free perovskite materials continue to attain extensive consideration in the field of solar cell applications due to their promising performances and non-toxicity. However, little information is available considering the detailed optimization of the device performance of lead-free perovskite solar cells. In this regard, a device made of ITO/WS₂/Cs₃Bi₂I₉/Cu₂O/Au was first optimized with ten (10) different back metal contacts, replacing Au. Besides, a comprehensive investigation was conducted considering the effect of absorber thickness, absorber acceptor density, and defect density on the performance of the device. The Cs₃Bi₂I₉ (absorber) layer, WS₂ (ETL), and Cu₂O (HTL) are optimized to ensure the optimum performance of the ITO/WS₂/Cs₃Bi₂I₉/Cu₂O/Ni architecture. After all possible optimizations, the PSC with ITO/WS₂/Cs₃Bi₂I9/Cu₂O/Ni structure offers much promising results with V_OC of 1.384 V, J_SC of 13.93 mA/cm², FF of 86.03%, PCE of 18.36%: opening new avenues for further research. In addition, the impact of working temperature, current density–voltage (J–V), and quantum efficiency are concurrently assessed for the best possible design. The champion cell configuration is also compared with earlier published experimental and theoretical studies available in the literature. In this study, a new lead-free PSC model has been developed, which demonstrates improved environmental friendliness, stability, and efficiency compared to previous models. Overall, the suggested methodology enables the realization of high-efficiency, eco-friendly solar cells, thereby offering a promising solution for the development of sustainable energy systems.