Kinetic study on ZnO nanorod-Cu ₂ O quantum dot heterojunctions in high-efficiency betavoltaic cells

To improve the energy-conversion efficiency of betavoltaic cells, we design an energy-conversion unit that couples zinc oxide (ZnO) nanorod arrays (ZNRAs) with cuprous-oxide (Cu 2 O) quantum dots (QDs) and evaluate it under a [Formula: see text]Ni source. Monte Carlo particle transport, combined with carrier-transport theory, is used to elucidate how material choices, structural parameters and device geometry govern beta ([Formula: see text]-particle energy collection, conversion and electrical output. For the ZNRAs-Cu 2 O architecture, a QD layer thickness of 200[Formula: see text]nm maximizes the [Formula: see text]-particle energy-transfer depth ([Formula: see text]1300[Formula: see text]nm), while a 25[Formula: see text]nm nanorod spacing provides a practical structural optimization threshold. Owing to its high molecular number density ([Formula: see text][Formula: see text]cm[Formula: see text]), ZnO acts as the principal energy-deposition region (total energy loss [Formula: see text]5670[Formula: see text]eV). Although the Cu 2 O QDs have a lower molecular number density ([Formula: see text][Formula: see text]cm[Formula: see text]) and a small thickness, they enhance carrier separation through quantum confinement and heterojunction synergy; the built-in field at the Cu 2 O/ZnO interface promotes drift transport. In the optimized structure, reduced defect impact extends carrier lifetime and improves collection efficiency, yielding a short-circuit current density of 0.0287[Formula: see text]mA cm[Formula: see text] and an open-circuit voltage of 0.447 V. These results reveal the synergistic-gain mechanism across the chain of “energy deposition[Formula: see text]carrier transport[Formula: see text]electrical conversion,“ providing a quantitative basis for analyzing and optimizing betavoltaic devices.