Quantitative modeling, optimization, and verification of Ni-63-powered betavoltaic cells based on three-dimensional ZnO nanorod arrays

Betavoltaic cells (BCs) are promising self-generating power cells with long life and high power density. However, the low energy conversion efficiency (ECE) has limitations in practical engineering applications. Wide-bandgap semiconductors (WBGSs) with three-dimensional (3-D) nanostructures are ideal candidates for increasing the ECE of BCs. This paper proposes hydrothermally grown ZnO nanorod arrays (ZNRAs) for Ni-63-powered BCs. A quantitative model was established for simulation using the parameter values of the dark characteristics, which were obtained from the experimental measurements for a simulated BC based on a Ni-incorporated ZNRAs structure. Monte Carlo (MC) modeling and simulation were conducted to obtain the values of the beta energy deposited in ZNRAs with different nanorod spacings and heights. Through the simulation and optimization of the 3-D ZNRAs and 2-D ZnO bulk structures, the performance of the Ni-63-powered BCs based on both structures was evaluated using a quantitative model. The BCs based on the 3-D ZNRAs structure and 2-D ZnO bulk structure achieved a maximum ECE of 10.1% and 4.69%, respectively, which indicates the significant superiority of 3-D nanostructured WBGSs in increasing the ECE of BCs.