High entropy perovskite oxide materials are a highly promising class of materials with a wide range of potential applications. They offer a unique combination of perovskite oxides and high entropy oxides, making them suitable for various fields, particularly in electrochemical energy storage systems and hydrogen production. Given the growing demand for clean energy and efficient energy storage solutions, the development of high entropy materials holds great significance. In this study, a cost-effective and rapid fabrication method was employed to produce several single-phase high entropy perovskite oxides by altering the B-site cations. The results demonstrated that these high entropy perovskite oxides could be synthesized with the same crystal structure, despite having significantly different elemental compositions. These variations in elemental composition led to differences in lattice parameters, metal-oxygen bond strengths, and oxygen vacancy content within the materials. Understanding and manipulating these factors can have important implications for the design of high entropy materials for energy storage and other applications.

In this work, a sustainable solution-based route was employed to synthesize a ZnONPs/PEI N-GQDs nanocomposite by integrating zinc oxide nanoparticles into polyethylenimine-functionalized nitrogen-doped graphene quantum dots. The primary optoelectronic properties of the synthesized material in liquid phase were evaluated by UV–Vis spectroscopy, and Tauc analysis indicated a direct optical band gap of approximately 3.0 eV. Photoluminescence (PL) spectroscopy further revealed a red-shifted visible emission centered at ∼518 nm, attributed to defect- and interface-mediated radiative recombination between ZnONPs and PEI-functionalized N-GQDs. Complementary structural characterization using FTIR, XPS, and TEM confirmed the successful formation of the hybrid nanocomposite, evidencing the coexistence of ZnO nanoparticles and PEI-functionalized N-GQDs. Ultraviolet photoelectron spectroscopy (UPS) was employed to elucidate the interfacial energy-level alignment, yielding a work function of ∼3.17 eV and indicating the formation of a Schottky contact at the metal/nanocomposite interface together with a type-II-like band alignment at the ZnONPs/PEI N-GQDs/n-Si junction. Two diode configurations were fabricated: a conventional Au/n-type Si Schottky diode and a heterojunction diode based on Au/ZnONPs/PEI N-GQDs/n-type Si. Their semilogarithmic current–voltage characteristics were systematically investigated under dark and illuminated conditions at room temperature. Compared with the Au/n-type Si reference, the heterojunction diode exhibited pronounced rectification and a significantly enhanced photoresponse. Illumination induced a substantial increase in reverse current due to photogenerated carriers, resulting in a decrease in the rectification ratio from 3.25 × 103 (dark) to 6.64 × 101 (light) at ±5 V, reflecting a trade-off between rectification and photosensitivity. While the Au/n-type Si diode showed a higher rectification ratio in the dark (2.17 × 104 at ±5 V) and a lower ideality factor (n = 5.06), the heterojunction device demonstrated improved illuminated performance with a reduced ideality factor of 3.17 and an increased barrier height of 0.76 eV, underscoring its potential for silicon-based optoelectronic applications.

High-entropy perovskite oxides (HEPOs) combine the compositional flexibility of perovskite oxides with the structural stability of high-entropy oxides, which enables tunable physicochemical properties and robust electronic structures. These attributes make HEPOs particularly attractive as bifunctional air cathode catalysts for alkaline rechargeable zinc−air batteries (ZABs). In this work, we synthesized a series of HEPOs with different A-site cation compositions, (LaX)(FeCoCrMnZn)O₃ (X = Sr, Nd, Ca), referred to as LaSr, LaNd, and LaCa. We effectively tailored the work function and oxygen vacancy concentrations by employing an A-site doping strategy, which significantly impact HEPOs electrocatalytic performance. Among the samples, LaNd displayed the lowest oxygen evolution reaction (OER) overpotential and fastest reaction kinetics, resulting from its reduced work function and enhanced oxygen vacancy density. Both mass and specific activity analyses confirmed LaNd’s superior OER performance compared to the other A-site variants. When incorporated as a cathode in ZABs, LaNd also exhibited excellent cycling stability and a prolonged operational lifetime, while maintaining competitive oxygen reduction reaction (ORR) activity, underscoring its capability as a reliable bifunctional catalyst. These findings demonstrate that precise A-site cation tuning, while maintaining a stable crystal structure, allows for controlled electronic structure and oxygen vacancy engineering, offering a practical route to optimize HEPO-based air cathodes and enhance the performance and durability of rechargeable ZABs.