Improving perovskite solar cell efficiency with Yb-Doped ZnO nanostructures through structural, optical and electrical investigations

This study investigates the structural, morphological, optical, and electrical properties of ytterbium (Yb)-doped zinc oxide (ZnO) nanostructures synthesized via the hydrothermal method, with the aim of enhancing their performance as electron transport layers (ETLs) in perovskite solar cells (PSCs). X-ray diffraction (XRD) confirmed the hexagonal wurtzite phase of ZnO and the emergence of Yb₂O₃ cubic phases at higher doping concentrations (3–7 %), accompanied by reduced crystallite size, increased lattice strain, and dislocation density. Scanning and transmission electron microscopy revealed a morphological transition from hexagonal to spherical nanoparticles, with agglomeration at elevated Yb levels. Optical analyses indicated a slight blue shift in the absorption edge and photoluminescence quenching with increasing dopant concentration, attributed to defect-induced non-radiative recombination. Electrical characterisation demonstrated reduced carrier concentration and improved electron mobility upon Yb doping, which enhanced charge transport. When integrated into PSCs, Yb-doped ZnO significantly improved photovoltaic performance, achieving a power conversion efficiency of 4.70 % at 7 % doping—an 81 % increase compared to the undoped ZnO-based device. These findings highlight the potential of Yb-doped ZnO nanostructures in optimizing ETLs for next-generation perovskite solar cells.