Betavoltaic nuclear batteries, leveraging beta-emitting radioisotopes, offer inherent advantages such as long-term reliability, high energy density, compact form factors, and robust resistance to interference, positioning them as promising power sources for self-powered portable or embedded microdevices.

This study aims to enhance the conversion efficiency and output power of betavoltaic batteries with comprehensive consideration of the effects of backscattering, depletion region width, diffusion length, and electrode structure on charge collection efficiency, conversion efficiency, and output power.

By optimizing the device and electrode structure, i.e., introducing a PIN structure with "concentration gradient I- layer", optimizing the depletion region width, doping concentration and electrode materials, and increasing the spacing between electrode grid lines, ⁶³Ni-SiC-based PIN junction betavoltaic batteries were successfully fabricated with higher overall conversion efficiency and output power. Both the Monte Carlo simulations and numerical computations were employed to obtain characteristic parameters of these developed batteries, and their performances were measured by experiments.

The fabricated batteries exhibit short-circuit currents, open-circuit voltages, output powers, and total conversion efficiencies ranging from 10.29 nA·cm^-2 to 13.43 nA·cm^-2, 1.32 V to 1.44 V, 11.66 nW·cm^-2 to 14.69 nW·cm^-2, and 2.24% to 2.82%, respectively. Compared with previous reported work, the open-circuit voltage, fill factor, and overall conversion efficiency increase by an average of 127.50%, 114.47%, and 512.10%, respectively. Moreover, the overall conversion efficiency is higher than those reported in the literature (0.5% to 1.99%).

These results indicate that the conversion efficiency and output power of betavoltaic batteries can be significantly improved by taking above-mentioned optimization measures, providing important theoretical guidance and experimental evidence for the design and fabrication of betavoltaic batteries.