Experimental and theoretical study of 90Sr/90Y-n-Si/ZnO betavoltaic battery and theoretical prediction of homojunction betavoltaic cells performance

Abstract

Today, betavoltaic batteries has been considered due to their high energy density and long life for operating electrical systems in inaccessible and hostile environments. Conventional electrochemical batteries, despite their widespread use in electronic devices, have a limited lifetime and tend to degrade in extreme environmental conditions. The current paper pursues three goals. The first goal is to the experimental and theoretical investigation of a n-Si/ZnO heterojunction betavoltaic battery based on ⁹⁰Sr/⁹⁰Y source. The second goal is to optimize ZnO, SnO₂, BN, and diamond homojunction betavoltaic cells in two planar and cubical models by Monte Carlo simulation (MCNP code). The third goal is to present a new approach for estimating the standard error in calculating the parameters of betavoltaic batteries. In order to fabrication of a n-Si/ZnO heterojunction, the ZnO nanospheres were placed on the n-Si (100) substrate using chemical bath deposition (CBD) technology. The Al and Au electrodes were deposited on the formed sample. Then this sample was exposed to the radiation of an external ⁹⁰Sr/⁹⁰Y source with an activity of 12.8 mCi. The experimental values obtained for the short circuit current (I_sc), open circuit voltage (V_oc), efficiency (η), and maximum output power (P_max) were 0.047 μA, 0.015 V, 3.4 × 10⁻⁴ percent, and 0.141 nW, respectively. To compare with the experiment, we investigated the n-Si/ZnO betavoltaic cell by MCNP code. In the simulation, the beta spectrum of the ⁹⁰Sr/⁹⁰Y source was considered. The calculated theoretical values for I_sc, V_oc, η, and P_max were 0.063 μA, 0.020 V, 6.4 × 10⁻⁴ percent, and 0.265 nW, respectively. The experimental results show that the simulation results can be valid. In the optimization of ZnO, SnO₂, BN, and diamond homojunction betavoltaic cells in two planar and cubical models by MCNP code, it was found that the I_sc, V_oc, η, and P_max of the cubical model are better compared to the planar model. In the cubical model, P_max of ZnO, SnO₂, BN, and diamond betavoltaic batteries is 2633.34 nW ± 0.16 %, 1670.49 nW ± 0.15 %, 198.20 nW ± 0.17 %, and 1315.24 nW ± 0.15 %, respectively. In other words, P_max of the ZnO betavoltaic battery is about 58 %, 1229 %, and 100 % more than P_max of SnO₂, BN, and diamond betavoltaic batteries, respectively. P_max of the SnO₂ betavoltaic battery is about 743 % and 27 % more than P_max of BN and diamond betavoltaic batteries, respectively. The results show that ZnO and SnO₂ betavoltaic batteries can perform better compared to BN and diamond betavoltaic batteries. Also, their growth process is less expensive compared to BN and diamond.