Output Current Density Research Articles

A Dual-Functional Triboelectric Nanogenerator Based on the Comprehensive Integration and Synergetic Utilization of Triboelectrification, Electrostatic Induction, and Electrostatic Discharge to Achieve Alternating Current/Direct Current Convertible Outputs.

Traditional alternating current (AC) and direct current (DC) triboelectric nanogenerators (TENGs), which are implemented via the pairwise coupling of triboelectrification, electrostatic induction, and electrostatic discharge, have been widely explored in various fields. In this work, the comprehensive integration and synergetic utilization of triboelectrification, electrostatic induction, and electrostatic discharge in a single device for the first time is realized, achieving a dual-functional TENG (DF-TENG) to produce an AC/DC convertible output. Distinguishing from the conventional TENGs, the coupling of triboelectrification and electrostatic discharge enables charge circulation between the dielectric tribo-layers, while electrostatic induction realizes charge transfer in the external circuit. This novel energy conversion mechanism has been proven to be applicable to a variety of materials, including polymers, fabrics, and semiconductors. The output mode of the DF-TENG can be tuned by adjusting the slider motion state, and its constant output current and power density can reach 1.51 mA m-2 Hz-1 and 398 mW m-2 Hz-1 , respectively, which are the highest records reported for constant DC-TENGs to date. This work not only provides a paradigm shift to achieve AC/DC convertible output, but it also exhibits high potential for extending the TENG design philosophy.

Nafion-mediated barium titanate-polymer composite nanofibers-based triboelectric nanogenerator for self-powered smart street and home control system

Incorporation of inorganic materials into a polymer matrix has drawn significant interest, as the process can improve the mechanical and triboelectric properties of composite products. However, well dispersion and long-term stability of the developed composites remain a challenge. In this paper, we propose a novel Nafion-functionalized barium titanate nanoparticles (BaTiO3 NPs)/polyvinylidene fluoride (PVDF) composite nanofibers based high-performance triboelectric nanogenerator (NBP-TENG), which can serve as a self-powered human-machine interface for a smart control system. Specifically, our method of introducing Nafion provides an excellent dispersion of BaTiO3 into the PVDF matrix. As a result, a highly stable dispersion is maintained for almost 6 months without any noticeable precipitation or agglomeration. Consequently, the excellent dispersion enhances the effective stress transfer at the interface between the BaTiO3 and PVDF, resulting in the remarkably improved negative surface potential in the BaTiO3/PVDF homogeneous composite nanofibers. The NBP-TENG allows the generation of high output voltage, current density, and power density of 307 V, 1.8 µA/cm2, and 1.12 mW/cm2, respectively, which are enhanced by ∼ 6.3, 7.1, and 3.7 times, respectively, compared to pristine PVDF nanofibers. The NBP-TENG is capable of powering dozens of commercial LEDs connected in series by manual tapping and demonstrates stable output performance even after 10,000 cycles of repeated contact separation. Moreover, the NBP-TENG can be utilized as a self-powered human-machine interactive interface for smart street and home control systems, with the advantages of promising reliability, cost-effectiveness, energy efficiency, and practicality.

Numerical investigation of baffle shape effects on performance and mass transfer of proton exchange membrane fuel cell

Flow channels with baffles can enhance the transport of reactants and improve the performance of proton exchange membrane fuel cell (PEMFC). In this study, five different structures of flow channels with baffles are proposed, and the mass transfer and cell performance of PEMFC with different baffled channels are compared by CFD method. The results show that the PEMFC with a cutting cylindrical baffle has the best performance with an output current density of 1.82 A/m2 when the voltage is 0.4 V. Baffle design can promote reaction gas transmission while also increasing reaction gas concentration in the channel. Due to the circular arc surface design of the cylindrical section, the mass transfer enhancement effect of cutting baffles is better. When the fluid passes through the baffles, the velocity magnitude also changes abruptly due to the disturbance effect, and the more effective convection brought about by the reactants being pushed into the catalytic layer can enhance the mass transfer in the PEMFC and obtain better performance. The presence of baffles will increase the accumulation of water, the smaller the cross-sectional area, the better the water removal effect. Vortex generation will result in large parasitic power, which is detrimental to the performance of the PEMFC.

Designing High Interfacial Conduction beyond Bulk via Engineering the Semiconductor-Ionic Heterostructure CeO2-δ/BaZr0.8Y0.2O3 for Superior Proton Conductive Fuel Cell and Water Electrolysis Applications.

Proton ceramic fuel cells (PCFCs) are an emerging clean energy technology; however, a key challenge persists in improving the electrolyte proton conductivity, e.g., around 10-3-10-2 S cm-1 at 600 °C for the well-known BaZr0.8Y0.2O3 (BZY), that is far below the required 0.1 S cm-1. Herein, we report an approach for tuning BZY from low bulk to high interfacial conduction by introducing a semiconductor CeO2-δ forming a semiconductor-ionic heterostructure CeO2-δ/BZY. The interfacial conduction was identified by a significantly higher conductivity obtained from the BZY grain boundary than that of the bulk and a further improvement from the CeO2-δ/BZY which achieved a remarkably high proton conductivity of 0.23 S cm-1. This enabled a high peak power of 845 mW cm-2 at 520 °C from a PCFC using the CeO2-δ/BZY as the electrolyte, in strong contrast to the BZY bulk conduction electrolyte with only 229 mW cm-2. Furthermore, the CeO2-δ/BZY fuel cell was operated under water electrolysis mode, exhibiting a very high current density output of 3.2 A cm-2 corresponding to a high H2 production rate, under 2.0 V at 520 °C. The band structure and a built-in-field-assisted proton transport mechanism have been proposed and explained. This work demonstrates an efficient way of tuning the electrolyte from low bulk to high interfacial proton conduction to attain sufficient conductivity required for PCFCs, electrolyzers, and other advanced electrochemical energy technologies.

Design of novel flow channels of tubular biomass-syngas fueled SOFC towards uniform temperature distribution

The solid oxide fuel cell (SOFC) may suffer structural damage even performance degradation caused by large temperature gradient at high temperature. Therefore, it is necessary to implement thermal management of SOFC to keep temperature gradients within safe limits. In such context, this work designs three novel flow channels and investigates their effects on SOFC temperature distribution characteristics and electrochemical performance. Three novel flow channels with semicircular, rectangular and trapezoidal disturbances are considered. It was found that the temperature gradient and maximum temperature can be decreased to a certain extent by setting the disturbance within the flow channel. Moreover, the rectangular disturbance is better than semicircular disturbance and trapezoidal disturbance in reducing temperature gradient. The maximum temperature and temperature gradient of the cell could be reduced from 880 °C to 840 °C and 24 K/cm to 12 K/cm, respectively by using rectangular disturbance. In the region with a large temperature gradient, increasing the disturbance depth can decrease the temperature gradient more effectively. However, around the region with a small temperature gradient, increasing the disturbance depth results in a large temperature gradient reversely. Moreover, increasing the disturbance depth also reduces the output current density and causes the increase of channel pressure drop. It is suggested to increase the depth of local disturbance where the temperature gradient is large and to reduce the depth of local disturbance where the temperature gradient is already small. By comparison with the decrease of channel thickness, the internal disturbance structure is beneficial to decrease temperature gradient when the air inlet flow rate is kept a constant.

Construction of a high power-density microbial fuel cell based on lipopolysaccharide-lectin interactions and its application for detecting heavy metal toxicity

• A Con A/AuNPs/CC electrode was facilely fabricated and used as novel anode material. • The interactions between Con A and bacterial lipopolysaccharide enable fast bacteria inoculation. • The interactions between Con A and bacterial lipopolysaccharide increase the bacterial loading capacity. • The proposed MFC can produce a maximal power density of 3362 mW cm -2 . • The MFC is used as a self-powered biosensor for heavy metal toxicity detection. Herein, we report the short startup time and high power density of a microbial fuel cell (MFC) based on lipopolysaccharide (LPS)-lectin interactions and its application for the detection of heavy metal toxicity. Concanavalin A (Con A) as a typical lectin is immobilized on a carbon cloth (CC) electrode with Au nanoparticles (AuNPs) as the bridge. The interactions between Con A and bacterial LPS can not only accelerate the inoculation speed of Shewanella putrefaciens but also increase the loading capacity of Shewanella putrefaciens on the anode. In addition, AuNPs on the Con A/AuNPs/CC anode can promote the direct extracellular electron transfer. Using the Con A/AuNPs/CC anode, the MFC produces a maximal power density of 3362 ± 120 mW m 2 , which is an order of magnitude higher than a CC anode based MFC. Taking Hg 2+ as an example, the MFC is used as a self-powered biosensor for toxicity detection in water. The output current density of the MFC decreases linearly with the increase of Hg 2+ concentration from 0.2 to 3 ppm, with a low detection limit of 0.05 ppm.

High performance direct current-generating triboelectric nanogenerators based on tribovoltaic p-n junction with ChCl-passivated CsFAMA perovskite

Herein, we develop direct current-generating triboelectric nanogenerators (DC-TENGs) based on the tribovoltaic p-n junction using n-type perovskite (CsFAMA) and p-type conductive polymer (PEDOT:PSS); CsFAMA based DC-TENG is shown to generate a high DC power output of about 2.1 µA cm−2 (current) and 0.33 V (voltage). We also introduce choline chloride (ChCl) to passivate the defects inside CsFAMA to improve the power-generating performance of DC-TENG by increasing triboelectric charge density, carrier mobility, and built-in potential, which are the key factors that determine device performance. Due to the synergetic effect of reduced defect sites (5.0×1015 cm−3 to 1.0×1015 cm−3), enhanced electron mobilities (1.0×10−2 cm2 V−1 s−1 to 2.3×10−2 cm2 V−1 S−1), and modulated work function, the passivated CsFAMA-based DC-TENG generates an output current density of 11 µA cm−2 and an output voltage of 0.80 V. Our results are expected to contribute to the development of high-performance DC-TENGs by presenting a promising strategy that involves controlling the triboelectric semiconducting interface.

Control of self-organization of drop-casted Nafion film for improving proton conduction in a polymer-electrolyte-membrane fuel cell to raise its output power density

A simple drop-cast method to directly deposit Nafion polymer electrolyte membrane (PEM) on nanostructured thin-film catalyst layer composed of stacked Pt nanoparticles prepared by pulsed laser deposition (PLD) was demonstrated. Through optimization of solvent composition and drying temperature of Nafion solution to control self-organization of Nafion, a uniform PEM with better bulk and interface microstructures could be produced, leading to a significant improvement in the output current density of a PEM fuel cell over that using reference commercial PEMs. The formation of facile proton conduction pathways in the bulk Nafion membrane resulted in a 35% reduction in ohmic resistance compared to that with the commercial membrane. Moreover, the infiltration of Nafion in the catalyst layer formed suitable proton transport network to render more catalyst nanoparticles effective and thus lower charge-transfer resistance. With the optimized PLD, drop-cast, and hot-pressing conditions, the current density of PEMFCs using drop-casted PEM reached 1902 mA cm−2 at 0.6 V at 2 atm H2 and O2 pressures with a cathode Pt loading of 100 μg cm−2, corresponding to a power density of 1.14 W cm−2 and a cathode mass-specific power density of 11.4 kW g−1.

Ru-doped lanthanum ferrite as a stable and versatile electrode for reversible symmetric solid oxide cells (r-SSOCs)

In the current scenario of innovative energy systems, reversible solid oxide cells (r-SOCs) are widely recognized as promising devices, thanks to their high conversion efficiency in both power-to-fuel and fuel-to-power modes. A crucial aspect for their scale-up is the development of multi-functional compounds that can work as either air or fuel electrodes. The most reliable alternative to conventional materials for r-SOCs are perovskite oxides. Sr-substituted lanthanum ferrites (LSF) show large mixed ionic and electronic conductivity (MIEC) and versatile catalytic activity upon B-site doping. Nevertheless, their poor stability in highly reducing environments precludes their widespread application. In this work, 5 mol% Ru-doped lanthanum ferrite La0.6Sr0.4Fe0.95Ru0.05O3-δ (LSFR05) is investigated as a multi-functional electrode for reversible and symmetric solid oxide cells (r-SSOCs). Ru-doping promotes LSF stability, retaining a higher lattice oxygen content. Upon reduction, LSFR05 exhibits exsolution of uniformly dispersed catalytically active Fe–Ru nanoparticles. All-perovskite symmetric cells showed remarkably high power density as H2–SOFC at 850 °C (602 mW cm−2), while in CO2-SOEC mode a current density output of 1.39 A cm−2 at 1.5 V was obtained. With a standard 70:30 CO2:CO gas composition, the cell showed a polarization resistance as low as 165 mΩ cm2. The complete SOFC-SOEC reversibility was successfully assessed for over 200 h.

Superior dimethyl disulfide degradation in a microbial fuel cell: Extracellular electron transfer and hybrid metabolism pathways

To enhance the biological degradation of volatile organic sulfur compounds, a microbial fuel cell (MFC) system with superior activity is developed for dimethyl disulfide (DMDS) degradation. The MFC achieves a removal efficiency near 100% within 6 h (initial concentration: 90 mg L−1) and a maximum biodegradation rate constant of 0.743 mM h−1. The DMDS removal load attains 2.684 mmol h−1 L−1, which is 6.18–2440 times the loads of conventional biodegradation processes reported. Meanwhile, the maximum power density output and corresponding current density output are 5.40 W m−3 and 40.6 A m−3, respectively. The main mechanism of extracellular electron transfer is classified as mediated electron transfer, supplemented by direct transfer. Furthermore, the mass balance analysis indicates that methanethiol, S0, S2−, SO42−, HCHO, and CO2 are the main intermediate and end products involved in the hybrid metabolism pathway of DMDS. Overall, these findings may offer basic information for bioelectrochemical degradation of DMDS and facilitate the application of MFC in waste gas treatment. Environmental implicationDimethyl disulfide (DMDS), which features poor solubility, odorous smell, and refractory property, is a typical pollutant emitted from the petrochemical industry. For the first time, we develop an MFC system for DMDS degradation. The superior DMDS removal load per unit reactor volume is 6.18–2440 times those of conventional biodegradation processes in literature. Both the electron transfer route and the hybrid metabolism pathway of DMDS are cleared in this work. Overall, these findings give an in-depth understanding of the bioelectrochemical DMDS degradation mechanism and provide an efficient alternative for DMDS removal.

Multi-objective optimization of graded catalyst layer to improve performance and current density uniformity of a PEMFC

The optimal use of compositions (platinum and ionomer) in cathode catalyst layers (CCLs) is essential to enhance the performance and improve the current density uniformity of proton exchange membrane fuel cells (PEMFCs). This paper presents a numerical study of graded CCL for a PEMFC. A one-dimensional, two-phase, non-isothermal model is developed, and the concept of the high power range (HPR) is defined. The effects of operating voltage and composition gradients across the catalyst layer thickness on output performance and current density distribution are investigated within the HPR. The results show an intense conflict between the output performance and current density uniformity, and only when biasing ionomer toward the membrane and operating in the higher spectrum of the HPR could improve them simultaneously. Otherwise, the improvement of one indicator means the deterioration of another. Finally, with the consideration of the interaction between the operating voltage and the gradients of platinum and ionomer, a multi-objective optimization is conducted to improve the aforementioned two indicators. Compared to the base case, the current density uniformity and the output performance were improved by 71.4% and 5.26%, respectively, which provides a solution to achieve higher performance and more uniform current density.

Evaluation and optimization of the Zn-based microfluidic microbial fuel cells to power various electronic devices

As an actual application, Zn-based microfluidic microbial fuel cells (MFCs) were investigated based on microchannel length and substrate flow rate in a straight geometry to power a variety of electronic devices. According to the statistical analysis based on response surface methodology (RSM), these parameters and their interactions are significant contributors to the system power generation. Based on the RSM, the optimum condition was determined to maximize the generated power density. A single optimized microfluidic MFC cell produced an open circuit potential (OCP) of 1.295 V and an output power density and current density of 21111 W m-3 and 140000 A m-3, respectively. In terms of bioelectrical characteristics, these are the highest values yet achieved by microfluidic MFCs. Several series and parallel configurations of the optimized cells were tested to demonstrate that they can provide sufficient power to a mechanical desktop clock, a digital alarm clock thermometer, and a coreless motor without using voltage or current boosters.

Construction of anodic electron transfer chain based on CuCl2/TiOSO4 synergetic mediators for highly efficient conversion of biomass wastes into electricity at low temperature

Biomass flow fuel cells (BFFCs) are promising alternatives for large-scale conversion of biomass into electricity at low temperature. However, most of them are based on single redox-active materials in anolyte which have limited capacity density and electron transfer rate, resulting in many natural biomass residues can’t generate electricity rapidly and efficiently. Herein, we develop a new anodic electron transfer chain based on CuCl2/TiOSO4 synergetic mediators for BFFCs. The density functional theory (DFT) simulation and experiment results show that TiO2+/Ti3+ redox couple works as an intermediate medium to construct a CuCl2/TiOSO4 synergetic electron transfer chain, which strengthens the electron transfer rate between anolyte and graphite felt (GF) electrode. The CuCl2/TiOSO4 synergetic mediators can efficiently and rapidly degrade glucose, industrial lignin and other natural biomasses at low temperature, and extract electrons simultaneously for generating electricity. The maximum power density (Pmax) of CuCl2/TiOSO4-based BFFC is 146.7 mw·cm−2 when the anolyte is pre-reacted at 90 ℃ for 1 h with glucose as fuel and paired with VO2+/VO2+ catholyte. And the fuel cell can discharge electricity continuously and stably for more than 6 h at 400 mA·cm−2. Furthermore, it can stably power LED pattern with 92 bulbs. Besides, when the CuCl2/TiOSO4-based BFFC utilizes sodium lignosulfonate as fuel, its Pmax is 55.1 mW·cm−2, and the BFFC can discharge electricity stably for more than 1 h at high output current density of 1.3 A·cm−2. This work provides a promising approach for application in direct biomass wastes power generation.

Simultaneously Enhancing Direct‐Current Density and Lifetime of Tribovotaic Nanogenerator via Interface Lubrication

AbstractTribovoltaic nanogenerators (TVNGs) present great properties such as high direct‐current density and continuous output performance, which has great potential to solve the power supply problem for miniaturized electronic devices. However, the severe wear problem of TVNG causes rapid attenuation of current density, which is difficult to realize long‐term operation with high output. In this work, an effective strategy via interface lubrication is proposed to enhance the direct‐current density and lifetime of TVNGs simultaneously. The water‐based graphene oxide solution is utilized as a lubricant, which can increase the sliding surface carriers to enhance current density, and reduce the wear between the copper and the silicon wafer surface due to its excellent lubrication performance. Hence, the TVNG can generate peak current density output ≈775 mA m−2, accompanied with 31 mC m−2 transfer charges density. The TVNG via interface lubrication can maintain high current output after 30 000 cycles. In addition, it can combine with triboelectric nanogenerator to constitute a dual‐type signal sensor, which can be used to monitor bridge vibration and goods’ weight. This study provides an effective method to solve the wear problem of TVNG and improve direct‐current density simultaneously, which will accelerate the practical application of TVNGs in the future.

Theoretical prediction of output performance of 63NiO-Si heterojunction betavoltaic cell

For the 63NiO-Si heterojunction betavoltaic nuclear battery, the energy deposition of the energy conversion material itself was simulated by Monte Carlo simulation, and the structure of the 63NiO-Si heterojunction was optimized based on the theoretical calculation results. When the thickness of 63NiO is 4 μm and the doping concentration of Si is 1 × 1015 cm−3, the short-circuit current density, open-circuit voltage, fill factor, and maximum output power density of the nuclear battery are 1.22 μA · cm−2, 3.17 V, 0.95, 3.67 μW · cm−2. In addition, the output performance of 63Ni/NiO-Si heterojunction betavoltaic nuclear cell was calculated in this study. Under the condition that the activity of the radioactive source and the thickness of NiO(63NiO) are the same in the two structures, the proposed structure (63NiO-Si) has greatly improved the output performance of the nuclear battery by reducing the energy lost from radioactive source self-absorption.

Ferroelectric LaxFe0.1–x Codoped ZnO Nanorod Triboelectric Nanogenerators for Electrochemical Rhodamine B Degradation

LaxFe0.1–x codoped ZnO nanorod arrays have been successfully prepared by the simple hydrothermal method, and the concentration ratio of 1:1 of Fe and La endows the codoped ZnO arrays with optimal ferroelectric properties. Then the ferroelectric La0.05Fe0.05 codoped ZnO nonoarrays and polydimethylsiloxane (PDMS) are used as positive and negative friction materials, respectively, to assemble the triboelectric nanogenerators (TENGs). Compared with Fe- or La-doped ZnO positive friction materials, the La0.05Fe0.05 codoped ZnO positive friction layer increases the output current density of TENGs by nearly 10 times, and the TENGs have excellent output stability. Lastly, the La0.05Fe0.05 codoped ZnO/PDMS TENGs have been successfully used for the high-efficient electrocatalytic degradation of RhB in simulated seawater. The work is very beneficial to the development of self-powered electrochemical degradation of organic pollutants in wastewater.

Ink‐printed metal/graphene aerogel for glucose electro‐oxidation

AbstractThree‐dimensional (3D) printing has become one of the promising technologies for the development of bulk‐sized nanomaterial composites for electrocatalysis. However, traditional methods such as field deposition modeling and stereolithography are not suitable for the development of functionalized materials for practical use. A large number of studies have focused on the development of the direct ink writing (DIW) printing technique for the fabrication of graphene aerogel (GA)‐based electrodes with binders for electrocatalysis. Only a few studies have focused on the synthesis of GA materials from binder‐free graphene oxide (GO) using the DIW 3D printing method. Here, we describe the preparation of GA‐based electrodes (without size contraction) with different Pd–Pt loadings using the DIW printing method with a commercial 3D food printer. The electron microscopy results showed that a Pd–Pt/GA monolith with a high Pd–Pt loading (59.43 wt%) could be obtained. The DIW‐printed Pd–Pt/GA‐2 electrode showed good electrochemical performance in glucose electrooxidation (GOR), with a high output current density of 0.94 A g−1 in 0.3 M glucose/1 M NaOH solution at the 3000th cycle operation (60 h). This study shows the potential of DIW‐printed binder‐free Pd–Pt/GA electrodes for use in fuel cell applications.

Durum wheat semolina-modified ceramic membranes as novel porous separators for enhanced power generation and wastewater remediation using microbial fuel cell

This proof-of-concept study describes the enhanced performance efficiency of the dual-chambered microbial fuel cell equipped with the fabricated unmodified ceramic membranes and ceramic membranes modified with 5 % and 10 % (w/w) durum wheat semolina in comparison with the commercially available NafionTM 117 membranes. The chemical oxygen demand removal efficiencies were determined to be 85.6 ± 0.1, 72.1 ± 0.2 and 68.6 ± 0.1 % for microbial fuel cell equipped with 10 % (w/w) semolina-modified, 5 % (w/w) semolina-modified and unmodified ceramic membrane, respectively, which indicated the improved wastewater treatment efficiency with increasing content of semolina. Preliminary studies showed that the 10 % (w/w) semolina-modified ceramic was cost-effective (64 USD/m2) with improved water uptake, good proton mobility, low oxygen diffusion in addition to the enhanced power and current density output. The semolina-modified ceramic membranes have the potential to become a cost-effective alternative for the high-efficiency production of bioelectricity using microbial fuel cells.

First demonstration of hetero-epitaxial ε-Ga2O3 MOSFETs by MOCVD and a F-plasma surface doping

This letter reports on the demonstration of ε-phase gallium oxide (ε-Ga2O3) based metal-oxidesemiconductor field effect transistors (MOSFETs) for the first time. Phase-pure ε-Ga2O3 film was hetero-epitaxially grown on a sapphire substrate by metal organic chemical vapor deposition (MOCVD) using a two-step growth method. The high crystalline quality of the epilayer was confirmed with the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations. Through a proper surface cleaning and CF4-plasma treatment process, fluorine (F) atoms were incorporated and acted as donors in the ε-Ga2O3 film, by which the sheet resistance (Rsh) of the epilayer was decreased by 105. Based on this F-plasma doped ε-Ga2O3 film, MOSFETs with a maximum output current density exceeding 3 mA/mm were successfully demonstrated. The doping profile extracted from the capacitance-voltage (C-V) measurement showed a significant carrier accumulation near the ε-Ga2O3 film surface with a peak concentration of 5 × 1017 cm−3 and an integrated carrier density of ∼6.4 × 1011 cm−2. The peak electron effective mobility (μeff) within the MOSFET channel was extracted to be as high as 19 cm2/Vs, indicating a great potential of ε-Ga2O3 based electronics for future high-speed and high-power applications.

Modeling and optimization of GaN-based betavoltaic batteries: Comparison of p–n and p–i–n junctions

Nuclear battery is a promising long-life power source. Selecting semiconductors with high limit efficiency and appropriate device structures effectively improves their output performance. In this work, a GaN-based (hexagonal) betavoltaic battery with Ni63 source was simulated by Monte Carlo codes and COMSOL Multiphysics, and the energy converters, including p–n junction and p–i–n junction, were compared and optimized. We analyzed the effects of thickness and doping concentration of each region on the battery performances. The p-region and n-region thickness and doping concentration of the p–n junction-based battery are 0.5, 9.5 µm, 1017 cm−3, and Nd = 1016 cm−3, which can achieve 3.77% conversion efficiency, and the short-circuit current density, open-circuit voltage, and maximum output power density are 0.074 µA/cm2, 2.01 V, and 0.125 µW/cm2, respectively. For the p–i–n junction-based battery, when the thickness and the doping concentration of p-region, i-region, and n-region are 0.5, 3, 6.5 µm, 1017, 1014, and 1016 cm−3, respectively, the conversion efficiency, short-circuit current density, open-circuit voltage, and maximum output power density are 5.03%, 0.099 µA/cm2, 2.0 V, and 0.167 µW/cm2, respectively. By comparing the output parameters of the two types of batteries, the results indicate that the p–i–n junction has a wider depletion region and better output performance compared with the p–n junction.