Zinc and [Zinc, Nickel]: co‑doped SnO2 nanoparticles as prospective electron transport layer materials for efficient lead free-MASnI3 perovskite solar cells

In this study, we explore the potential of both pristine and doped tin oxide (SnO2) as promising materials as the electron transport layer (ETL) for efficient lead free-methylammonium tin iodide (MASnI3) perovskite solar cells (PSCs). The pristine, Zinc (Zn) doped, and Nickel (Ni)-Zn co-doped SnO2 nanoparticles with a constant concentration of Zn while changing the concentration of Ni were synthesized by using the hydrothermal method. The effect of doping and co-doping on optical, structural, and electrical properties of SnO2 nanoparticles was investigated using different microscopic and spectroscopic tools. The X-ray diffractograms showed that pristine, doped, and co-doped SnO2 nanoparticles have better crystallinity and tetragonal rutile crystal structure. The fingerprint functional groups and elemental composition were confirmed by FTIR absorption peaks, EDX, and XPS, respectively. The UV-Vis DRS spectroscopy results revealed that the optical band gap reduced from 2.90 eV for pristine SnO2 to 2.26 eV for co-doped 1 weight (wt) % Ni-Zn-SnO2 nanoparticles and can be tuned with a variation of wt % of Ni. Further, the photoluminescence emissions of all SnO2 nanoparticles in the range of 307 to 494 nm are related to oxygen vacancies or defects. Moreover, BET results confirms larger surface area for 1 wt % Ni-Zn-SnO2, which can help in better electron-hole pair separation. The electrical conductivity studies confirm that the synthesized nanoparticles exhibit excellent ohmic contact behavior and show a notable increase in electrical conductivity for 1 wt% Ni-Zn-SnO2 nanoparticles. Further, the suitability of both pristine and doped SnO2 as ETL material for the MASnI3-based PSCs was simulated using SCAPS-1D software. The best power conversion efficiency of 29.60 % was achieved for FTO/1 wt % Ni-Zn-SnO2/MASnI3/Spiro-OMeTAD/Au. This investigation highlights the potential of co-doped materials as promising candidates for the development of efficient PSCs.