Modulating Mn-doped NiO nanoparticles: structural, optical, and electrical property tailoring for enhanced hole transport layers

Mn-doped NiO nanoparticles (NPs), denoted as Ni_1-<i>x</i> Mn _<i>x</i> O with <i>x</i> values of 0.00, 0.02, 0.04, 0.06, and 0.08, were synthesized using a chemical precipitation process. These NPs were comprehensively analyzed for their structural, optical, and electrical properties, along with their surface morphology and elemental composition. X-ray Diffraction (XRD) confirmed the single-phase cubic crystal structure and revealed a reduction in crystallite size from 15.26 nm to 10.38 nm as Mn doping increased. Field Emission Scanning Electron microscopy (FE-SEM) determined the average particle sizes ranging from 26.03 nm to 23.30 nm. The optical properties, assessed by UV-visible spectroscopy (UV-vis), revealed a widening of the bandgap from 3.49 eV to 4.10 eV with increasing Mn doping, suggesting tunable optical characteristics. X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of nickel (Ni), oxygen (O), and manganese (Mn) within the NPs. The highest mobility, 1.31 ± 0.03 × 10³ cm² V^-1 s^-1, was observed in the 6 wt% Mn-doped NiO NPs thin film, as determined by Hall measurements. To assess their practical utility, SCAPS-1D simulation was employed, demonstrating the potential of Mn-doped NiO NPs as a hole transport layer (HTL) in perovskite solar cells (PSCs). The enhanced electrical and optical properties, combined with structural tunability, highlight Mn-doped NiO as a promising material for advanced optoelectronic applications. This study provides valuable insights into the development of efficient and stable solar cells, offering a pathway to optimize material design for improved performance in photovoltaic applications.