Enhancing the efficiency of earth-abundant Zn3P2 SCs by in-depth numerical analyses on various hole transport layers

A heterojunction solar cell (SC) utilizing earth-abundant, cost-effective, and stable zinc phosphide (Zn₃P₂) as the absorber layer, alongside with highly transparent and high-band-gap magnesium-doped zinc oxide (MZO) as the junction partner, was investigated by utilizing SCAPS-1D simulator. This innovative device architecture allowed for an in-depth evaluation of crucial parameters such as layer thickness, carrier density, and defect densities, facilitating the identification of the optimal conditions for the SCs. Following the optimization of the Zn3P₂ layer, as a hole transporting materials, additional materials—specifically NiO, Cu₂O, nitrogen-doped copper oxide (NCO), and copper gallium selenide (CGSe) were systematically integrated with MZO/Zn₃P₂ configuration to further enhance the overall cell performance. Comprehensive analyses were conducted to assess various aspects of the solar cell performance, including energy band structure, work function of the back contact metal, operating temperature ranges, quantum efficiency (QE) analysis at different wavelengths of light. Additionally, recombination analysis at both interfaces of the device with different configuration such as MZO/Zn₃P₂/NiO, MZO/Zn₃P₂/Cu₂O, MZO/Zn₃P₂/CGSe, and MZO/Zn₃P₂/NCO were investigated systemetically. Among the configurations explored, the MZO/Zn₃P₂/NCO structure emerged as the most effective, demonstrating stable operation over a wide temperature range. This configuration exhibited a significantly higher built-in potential compared to other designs, coupled with low recombination rates and a reduced surface recombination velocity (SRV) at the rear side. Such enhancements culminated in an impressive photoconversion efficiency of 20.5 %, with a short-circuit current density of 21.15 mA/cm², an open-circuit voltage of 1.15 V, and a fill factor of 81.9 %. These promising results not only highlight the potential of the Al/FTO/MZO/Zn₃P₂/NCO/Ni solar cell as an efficient solar energy harvester but also underscore its viability as a sustainable alternative in the pursuit of renewable energy solution.