Betavoltaic Microbattery Research Articles

Betavoltaic battery prepared by using polycrystalline CdTe as absorption layer

Betavoltaic microbattery is the main energy supply unit in MEMS, which has the advantages of stable performance, long service life, high energy density and small scale. The current paper presented a design scheme of betavoltaic microbattery with semiconductor material polycrystalline CdTe and 3H radioactive source. In this paper, the properties of polycrystalline CdTe films with different thicknesses and the performance of corresponding devices were tested. In the proposed design scheme, an average energy of 5.7 keV was deposited in the polycrystalline CdTe. The short circuit current density and open circuit voltage of a single device were 5.53 nA/cm2 and 111.2 mV respectively when the thickness of polycrystalline CdTe film was 400 nm.

Simulation and Optimization Design of SiC-Based PN Betavoltaic Microbattery Using Tritium Source

In this paper, the Monte Carlo method and numerical model are used to build the electrical model of a SiC-based betavoltaic microbattery using a 3H source, and the influences of structural parameters and the surface recombination effect on the output characteristics of the SiC PN battery are simulated. According to Monte Carlo calculations based on the energy spectrum of the 3H source, the ionization energy deposition approaches the exponential distribution along the depth direction, and most of the 22rs are concentrated near the material surface. The ionization energy deposition data is converted into non-equilibrium carrier information for the numerical simulation of the battery’s output characteristics. The simulation results show that the conversion efficiency of the battery rises first, and then decreases with the increase of the doping concentration of the N region. This is because the N region-doping affects the depletion region width and the built-in electrical potential at the same time. After considering the surface recombination effect, the conversion efficiency decreased significantly. Thinning the thickness of or moderately reducing the doping concentration of the P region will weaken the surface recombination effect.

Temperature dependence of 63Ni–Si betavoltaic microbattery

This paper theoretically presented the temperature effects on the 63Ni–Si betavoltaic microbattery irradiated by a source with different thicknesses and activity densities at a temperature range 170–340K. Temperature dependences of the monolayer and interbedded 63Ni–Si betavoltaics at 213.15–333.15K were tested with respect to calculations. Results showed that the higher the thickness, activity density, and average energy of the source, the lower is the betavoltaic performance responds to temperature. With the increase in temperature, the Voc and Pmax of the upper, lower, and interbedded betavoltaics decreased linearly at low temperatures and decreased exponentially at high temperatures in the experiment. As predicted, the measured Voc and Pmax sensitivities of the lower betavoltaic with 4.90mCi/cm2 63Ni, −2.230mV/K and −1.132%, respectively, were lower than those with 1.96mCi/cm2 63Ni, −2.490mV/K and −1.348%, respectively. Compared with the calculated results, the prepared betavoltaics had lower Voc sensitivity and higher Pmax sensitivity. In addition, the measured Voc sensitivity of the interbedded betavoltaic in series is equal to the sum of those of the upper and lower ones as predicted. Moreover, the measured Pmax sensitivity of the interbedded betavoltaic is equal to the average of those of the two monolayers.

Prediction of 4H–SiC betavoltaic microbattery characteristics based on practical Ni-63 sources

We have investigated the performance of 4H–SiC betavoltaic microbatteries under exposure to the practical Ni-63 sources using the Monte Carlo method and Synopsys® Medici device simulator. A typical planar p–n junction betavoltaic device with the Ni-63 source of 20% purity on top is modeled in the simulation. The p–n junction structure includes a p+ layer, a p− layer, an n+ layer, and an n− layer. In order to obtain an accurate and valid predication, our simulations consider several practical factors, including isotope impurities, self-absorption, and full beta energy spectra. By simulating the effects of both the p–n junction configuration and the isotope source thickness on the battery output performance, we have achieved the optimal design of the device and maximum energy conversion efficiency. Our simulation results show that the energy conversion efficiency increases as the doping concentration and thickness of the p− layer increase, whereas it is independent of the total depth of the p–n junction. Furthermore, the energy conversion efficiency decreases as the thickness of the practical Ni-63 source increases, because of self-absorption in the isotope source. Therefore, we propose that a p–n junction betavoltaic cell with a thicker and heavily doped p− layer under exposure to a practical Ni-63 source with an appreciable thickness could produce the optimal energy conversion efficiency.

Single-walled carbon nanotube film-silicon heterojunction radioisotope betavoltaic microbatteries

Ever since the appearance of nanomaterials and nanotechnologies, they have been used in almost every type of microbattery except for nuclear ones. Here we present a radioisotope betavoltaic (BV) microbattery based on a single-walled carbon nanotube (SWCNT) film that acts as a carrier separator. SWCNT film also provides a shortcut for carrier transportation. The energy conversion efficiency of a BV microbattery can reach up to 0.15% after the subtraction of the energy loss of beta particles in air and SWCNT film, proving that the SWCNT film-silicon heterojunction presents a promising configuration suitable for use in radioisotope BV microbatteries. Tracing the particle route, we achieved a charge collection rate of 59.9%, indicating that our device could potentially achieve higher performance. Primary strategies to improve the performance of the BV microbattery are discussed.

Optimization and temperature effects on sandwich betavoltaic microbattery

The design scheme of a sandwich-structure betavoltaic microbattery based on silicon using 63Ni is presented in this paper. This structure differs from a monolayer energy conversion unit. The optimization of various physical parameters and the effects of temperature on the microbattery were studied through MCNP. For the proposed optimization design, P-type silicon was used as the substrate for the betavoltaic microbattery. Based on the proposed theory, a sandwich microbattery with a shallow junction was fabricated. The temperature dependence of the device was also measured. The open-circuit voltaic (Voc) temperature dependence of the optimized sandwich betavoltaic microbattery was linear. However, the Voc of the betavoltaic microbattery with a high-resistance substrate exponentially decreased over the range of room temperature in the experiment and simulation. In addition, the sandwich betavoltaic microbattery offered higher power than the monolayer betavoltaic one. The results of this paper provide a significant technical reference for optimizing the design and studying temperature effects on betavoltaics of the same type.

Design and simulation of GaN based Schottky betavoltaic nuclear micro-battery

The current paper presents a theoretical analysis of Ni-63 nuclear micro-battery based on a wide-band gap semiconductor GaN thin-film covered with thin Ni/Au films to form Schottky barrier for carrier separation. The total energy deposition in GaN was calculated using Monte Carlo methods by taking into account the full beta spectral energy, which provided an optimal design on Schottky barrier width. The calculated results show that an 8μm thick Schottky barrier can collect about 95% of the incident beta particle energy. Considering the actual limitations of current GaN growth technique, a Fe-doped compensation technique by MOCVD method can be used to realize the n-type GaN with a carrier concentration of 1×1015cm−3, by which a GaN based Schottky betavoltaic micro-battery can achieve an energy conversion efficiency of 2.25% based on the theoretical calculations of semiconductor device physics.

A high open-circuit voltage gallium nitride betavoltaic microbattery

A high open-circuit voltage betavoltaic microbattery based on a gallium nitride (GaN) p–i–n homojunction is demonstrated. As a beta-absorbing layer, the low electron concentration of the n-type GaN layer is achieved by the process of Fe compensation doping. Under the irradiation of a planar solid 63Ni source with activity of 0.5 mCi, the open-circuit voltage of the fabricated microbattery with 2 × 2 mm2 area reaches as much as 1.64 V, which is the record value reported for betavoltaic batteries with 63Ni source, the short-circuit current was measured as 568 pA and the conversion effective of 0.98% was obtained. The experimental results suggest that GaN is a high-potential candidate for developing the betavoltaic microbattery.

Optimization design of GaN betavoltaic microbattery

Betavoltaic radioisotope microbatteries have gradually become the research direction of micro-power sources because of their several advantages, including small scale, stable output performance, long service life, high energy density, strong anti-jamming capability, and so on. Based on the theory of semiconductor physics, the current paper presented a design scheme of isotope microbattery with wide-gap semiconductor material GaN and isotope 147Pm. In consideration of the isotope’s self-absorption effect, the current paper studied and analyzed the optimization thickness of semiconductor and isotope source, junction depth, depletion region thickness, doping concentration, and the generation and collection of electron hole pairs with simulation of transport process of beta particles in semiconductor material using Monte Carlo simulation program MCNP. In the proposed design scheme, for a single decay, an average energy of 28.2 keV was deposited in the GaN, and the short circuit current density, open circuit voltage, and efficiency of a single device were 1.636 μA/cm2, 3.16 V, and 13.4%, respectively.

Demonstration of a High Open-Circuit Voltage GaN Betavoltaic Microbattery

A high open-circuit voltage betavoltaic microbattery based on a GaN p-i-n diode is demonstrated. Under the irradiation of a 4×4 mm2 planar solid 63Ni source with an activity of 2 mCi, the open-circuit voltage Voc of the fabricated single 2×2mm2 cell reaches as high as 1.62 V, the short-circuit current density Jsc is measured to be 16nA/cm2. The microbattery has a fill factor of 55%, and the energy conversion efficiency of beta radiation into electricity reaches to 1.13%. The results suggest that GaN is a highly promising potential candidate for long-life betavoltaic microbatteries used as power supplies for microelectromechanical system devices.