Exploring RbGeI₃ based perovskite solar cells: a comprehensive DFT study and SCAPS analysis with copper-based hole transport layers

• Published in: Optical and quantum electronics Vol. 57; no. 8
• Main Authors: Raj, Manasvi, Aggarwal, Anshul, Kushwaha, Aditya, Goel, Neeraj
• Format: Journal Article
• Language: English
• Published: New York Springer US 18.07.2025; Springer Nature B.V
• Subjects: Absorbers; Characterization and Evaluation of Materials; Charge transport; Computer Communication Networks; Copper; Cost effectiveness; Density functional theory; Electrical Engineering; Electromagnetic absorption; Electron transport; Energy conversion efficiency; Interfacial properties; Lasers; Lead free; Open circuit voltage; Optical Devices; Optical properties; Optics; Optimization; Perovskites; Photonics; Photovoltaic cells; Physics; Physics and Astronomy; Short circuit currents; Solar cells; Stability; Tin oxides; Titanium dioxide; Solar cell; Perovskite; RbGeI; Hole transport layers
• ISSN: 1572-817X; 0306-8919; 1572-817X
• DOI: 10.1007/s11082-025-08373-z

This study investigates the structural, electronic, and optical properties of RbGeI₃ as a lead-free perovskite absorber using Density Functional Theory (DFT) calculations and SCAPS-1D simulations. DFT analysis confirms its stable orthorhombic structure, suitable bandgap, high dielectric constant, and strong visible-light absorption, making it a promising material for photovoltaic applications. To optimize device performance, we designed RbGeI₃-based perovskite solar cells (PSCs) with fluoride-doped tin oxide (FTO) as the front electrode, titanium dioxide (TiO₂) as the electron transport layer (ETL), and five different copper-based hole transport layers (HTLs), including CuO, CuSbS₂, Cu₂O, CuSCN, and CuI. Copper-based HTLs were chosen for their high conductivity, stability, cost-effectiveness, and ease of fabrication compared to conventional organic HTLs. Our optimization of absorber thickness, doping concentrations, and interfacial properties identified CuI as the most efficient HTL, achieving a power conversion efficiency of 18.97%, an open-circuit voltage of 0.777 V, a short-circuit current density of 33.969 mA/cm², and a fill factor of 71.93%. This study presents the first systematic evaluation of copper-based HTLs in RbGeI₃ PSCs, demonstrating their advantages in charge transport and stability. By integrating a lead-free absorber with low-cost, scalable inorganic HTLs, our work contributes to the development of high-efficiency and environmentally sustainable PSCs.