Enhancing betavoltaic nuclear battery performance with 3D P⁺PNN⁺ multi-groove structure via carrier evolution

Betavoltaic nuclear batteries offer a promising alternative energy source that harnesses the power of beta particles emitted by radioisotopes. To satisfy the power demands of microelectromechanical systems (MEMS), 3D structures have been proposed as a potential solution. Accordingly, this paper introduces a novel 3D ⁶³Ni–SiC-based P⁺PNN⁺ structure with a multi-groove design, avoiding the need for PN junctions on the inner surface, and thus reducing leakage current and power losses. Monte Carlo simulations were performed considering the fully coupled physical model to extend the electron–hole pair generation rate to a 3D structure, enabling the efficient design and development of betavoltaic batteries with complex 3D structures. As a result, the proposed model produces the significantly higher maximum output power density of 19.74 µW/cm² and corresponding short-circuit current, open-circuit voltage, and conversion efficiency of 8.57 µA/cm², 2.45 V, and 4.58%, respectively, compared with conventional planar batteries. From analysis of the carrier transport and collection characteristics using the COMSOL Multiphysics code, we provide deep insights regarding power increase, and elucidate the discrepancies between the ideal and simulated performances of betavoltaic batteries. Our work offers a promising approach for the design and optimization of high-output betavoltaic nuclear batteries with a unique 3D design, and serves as a valuable reference for future device fabrication.