Zinc Oxide Co-Doped with Aluminium and Boron (Al:B:ZnO) Thin Films via Sol–Gel Process for Solar Cell Window Layers: A Review

Solar energy is the most economical and plentiful long-term natural resource currently accessible. The rate of global economic growth and technical advancement is increasingly dependent on the need for cost-effective, high-performance optoelectronic devices. Zinc oxide (ZnO) films have garnered significant interest as viable substitutes for traditional transparent conductive oxides (TCOs) in solar systems. Zinc oxide nanoparticles (ZnONPs) are among the most extensively used metal oxide nanoparticles, garnering international scientific attention owing to their distinctive optical and chemical properties, biocompatibility, low toxicity, sustainability, and cost-effectiveness. The adaptability of ZnO enables doping with transition metals to improve its structural, electrical, optical, and magnetic properties. Doping with aluminium (Al) enhances electrical conductivity and optical clarity, while boron (B) doping reduces electrical resistivity and optical bandwidth while augmenting carrier concentration. Doping with a single element often improves just one specific optical or electrical characteristic. Simultaneous doping with both Al and B mitigates this constraint, resulting in a synergistic action that improves optical and electrical characteristics. After receiving Al-B co-doping treatment, the resistivity of ZnO film dropped from 6.12 × 102 Ωcm to 2.07 × 10–4 Ωcm. Furthermore, the ZnO film's transmittance values, surface homogeneity, and figure of merit value significantly increased due to the presence of Al and B components. Every investigation shown that the advantageous physical features of Al–B co-incorporated ZnO films make them a viable substitute for ITO films in TCO applications. The simultaneous enhancement renders co-doped ZnO very appropriate for transparent conductive electrodes and window layers in solar cell applications.