Search

The investigation on the effect of illumination power intensities for a thermophotovoltaic (TPV) system is crucial to enhance the TPV cell performance. To date, the studies on the effect of illumination intensities were limited to solar photovoltaic cells application. Meanwhile, the reported work on the impact of infrared illumination intensities on TPV cells are done at limited temperatures and intensities. The effects of TPV intensities on all performance parameters are not comprehensively studied and fully elucidated. Therefore, this paper investigates the performance of indirect-bandgap Germanium (Ge) and direct-bandgap Indium Gallium Arsenide (InGaAs) cells under various TPV spectral irradiances. Silvaco TCAD simulation software was used to investigate the effect of blackbody temperatures ranging from 800 to 2000 K with different illumination intensities on the TPV cell performances. It was found that higher conversion efficiencies are achieved for both TPV cells under higher illumination intensities due to the increase in open-circuit voltage and fill factor. As the beam intensity increases for temperatures >1600 K, fill factor slowly increases for the Ge cell, but decreases for the InGaAs cell due to the increase in the I2Rs losses associated with the high current. The finding demonstrates that the open-circuit voltage of indirect-bandgap TPV cell is significantly increased with higher illumination intensities. The variations in cells performance are explicitly explained based on factors such as TPV design structure and the physical properties of semiconductor at varying illumination intensities. The performance of both TPV cells were also analyzed at the minimum optical losses. Average efficiencies of Ge and InGaAs TPV cells were increased to 26.05% and 27.92%, respectively, when the optical losses were minimized with anti-reflection coating and thicker absorber layer. The results of this work demonstrate that by detailed consideration of the effect of spectral irradiances, a high-performance TPV system can be developed.

Rapid depletion of fossil fuels due to the growing demand for energy has resulted in a worldwide concern to improve energy conversion efficiency. Yet, the energy conversion of conventional fossil fuel power generation plants remains relatively low (less than 40%) and a huge amount of energy is wasted in the form of heat, leading to global warming issues. Recycling and recuperating even a small portion of energy losses could provide a huge impact on energy saving and minimize the reliance on fossil fuels. Thermophotovoltaic system appears to be a potential candidate to capture, recover, and convert waste heat energy into useful electricity. This paper presents an overview of the recent development of thermophotovoltaic technology for waste heat recovery applications. Each component in the thermophotovoltaic system including thermophotovoltaic generator/heat source, thermal emitter, spectral filter and thermophotovoltaic cells is vital and can be engineered to achieve a better heat-to-electricity conversion efficiency. Recently, researchers have shown great interest in near-field thermophotovoltaic systems where higher power intensity can be captured by the thermophotovoltaic cell, thus improving the overall system performance. Furthermore, the potential locations for energy scavenging in thermal power plants is investigated based on the on-site temperature measurement. In Malaysia, it is estimated that around 3,831 GWh of waste heat energy could be saved in operational thermal power plants. This review will contribute to the knowledge for future development thermophotovoltaic systems in waste heat recovery applications while summarizing the potential locations for energy scavenging in thermal power plants.

The optimization of thermophotovoltaic (TPV) cell efficiency is essential since it leads to a significant increase in the output power. Typically, the optimization of In0.53Ga0.47As TPV cell has been limited to single variable such as the emitter thickness, while the effects of the variation in other design variables are assumed to be negligible. The reported efficiencies of In0.53Ga0.47As TPV cell mostly remain 0.53Ga0.47As TPV cell using the real coded genetic algorithm (RCGA) at various radiation temperatures. RCGA was developed using Visual Basic and it was hybridized with Silvaco TCAD for the electrical characteristics simulation. Under radiation temperatures from 800 to 2000 K, the optimized In0.53Ga0.47As TPV cell efficiency increases by an average percentage of 11.86% (from 8.5 to 20.35%) as compared to the non-optimized structure. It was found that the incorporation of a thicker base layer with the back-barrier layers enhances the separation of charge carriers and increases the collection of photo-generated carriers near the band-edge, producing an optimum output power of 0.55 W/cm2 (cell efficiency of 22.06%, without antireflection coating) at 1400 K radiation spectrum. The results of this work demonstrate the great potential to generate electricity sustainably from industrial waste heat and the multi-dimensional optimization methodology can be adopted to optimize semiconductor devices, such as solar cell, TPV cell and photodetectors.

Thermophotovoltaic (TPV) system harvests heat from thermal radiation where the photons are absorbed by a photovoltaic (PV) cell device and generates electrical energy. InGaAs is one of the popular III-V semiconductors material and has a great potential to be an efficient TPV cell if further optimization and improvements are made. In this paper, In 0.68 Ga 0.32 As with bandgap energy of 0.6 eV and cut-off wavelength at 2.1 $\mu \mathrm{m}$ is modeled and optimized using TCAD simulation software. InAsP buffer layers were incorporated to reduce 1.1% lattice-matched effect between the device layer and lnP substrate. The cell’s base and emitter layers were optimized by varying the thickness and the doping concentration of the cell layer individually under 1400 K blackbody spectrum. The optimization of emitter thickness and base doping concentration significantly contribute to a higher cell performance. An emitter thickness of 0.06 $\mu \mathrm{m}$ contributes to an efficiency ($\eta$) of 25.55% while a base doping concentration of 1 × 1016 cm−3 recorded 23.08% of $\eta$.

Narrow bandgap (NB) materials provide better potential for infrared radiation conversion to electricity from solar or various thermophotovoltaic (TPV) spectrums. Different NB materials generate diverse output performance depending on the properties of materials crystal and cell configuration. Decreasing the bandgap of the materials will improve the collection of longer wavelength photons, but that tends to increase the recombination rate and reduce cell efficiency $(\eta)$ . This paper investigates the performance of NB cells. Silvaco TCAD software was used to simulate the output performance of germanium (Ge), indium arsenide (InAs), gallium antimonide (GaSb), and indium gallium arsenide (InGaAs) cells under solar spectrum AM1.5 and 1000 K illumination spectrums. It was found that InGaAs is the most outstanding material for photovoltaic (PV) application and TPV application at 1000 K radiation temperature. The comparative study and conclusion drawn in this work highlight several limitations in NB cells configuration, such as the high surface recombination rate in GaSb and InAs TPV cell, which reduces photocurrent collection.

Copper-based cables have limitation of distributing power safely and efficiently for Internet of Things (IoTs) application as well as during emergency conditions. This research paper aims to demonstrate the power over fiber (PoF) distribution system network in the short-haul distance, as an alternative to copper-based cable. The maximum efficiency obtained for the full system was 12% at 450 mA of laser driving current. The obtained results clearly demonstrated that as the laser driving current increases from 50 mA to 450 mA, overall efficiency of the system increases. The prototype was designed with a low power output where the main parameter that affects the overall efficiency system is the optical to electrical conversion module. Prototype results demonstrated the potential of PoF for low power distribution system.

Gallium Antimonide (GaSb) Thermophotovoltaic (TPV) cell is a well-known device for waste-heat harvesting technology. To date, the conversion efficiency of the GaSb TPV cell remains low due to the presence of electrical and spectral losses. In this study, a GaSb TPV cell model is developed using the Silvaco TCAD simulation software. Validation on the simulation model was performed under atmospheric (AM) 1.5 standard test condition (STC) and TPV illumination conditions. Through the validation processes, a set of GaSb physical parameters that are reliable to be used for GaSb TPV cell simulation was established. Under AM1.5 testing condition, the electrical characteristic and performance of GaSb TPV of the reference cell were obtained from an experimental characterization on commercialized devices. A deviation in fill factor and cell efficiency was found between the cell sample and simulation model under AM1.5 illumination. This is due to the presence of resistance losses in the device. Nevertheless, a percentage error of below 3% was achieved under 1200 ° C TPV spectrum. Besides, it was found that a spectral filter that cuts at 2 μm increases the cell efficiency from 11.51% to 19.10% with a power output of 1.33 W/cm2. The finding in this study demonstrates the importance of minimizing the electrical losses and the determination of an optimal filtered spectrum wavelength for developing highperformance GaSb TPV cell.

Thermophotovoltaic (TPV) devices are known for capturing infrared radiation from a high temperature heat source and converting them into electricity. While InAs TPV cells have the ability to harvest radiation heat from temperature source below 1000 K, the best-reported homojunction InAs efficiency is only 0.6 % under 1000 K. This is due to the lack of an optimize structure for TPV application. This research work investigates on optimizing the emitter thickness for Indium Arsenide (InAs) based TPV cells. The electrical characteristics of the InAs TPV cell were simulated using the SILVACO TCAD software. The thickness of p-type emitter ranging from 0.1 to $2.3\ \boldsymbol{\mu} \mathbf{m}$ were investigated. As the emitter thickness increases, the open circuit voltage ( $\boldsymbol{V_{oc}}$ ) increases, while the short-circuit current density ( $\boldsymbol{J_{sc}}$ ) decreases. With the increase rate of $\boldsymbol{V_{oc}}$ which is faster than the decreasing rate of $\boldsymbol{J_{sc}}$ , the maximum power efficiency was achieved at an optimum thickness of $1.5\ \boldsymbol{\mu} \mathbf{m}$ . At 800 °C blackbody temperature, the highest power efficiency was acquired as 0.61 % at the optimum emitter thickness.

GaAs structures are commonly used in concentrated solar cell application, whereas the active region of the cell requires front surface field (FSF) and back surface field (BSF) to complete the band diagram and to improve the conversion efficiency up to 22 % under AM 1.5 illumination condition. However, the integration of different FSF and BSF materials such as AlGaAs, InGaP and InAlP contribute to diverse performance. A fair comparison between these materials will help to optimize the performance of GaAs devices. In this work, Silvaco TCAD software was used to simulate GaAs PV cell with different FSF and BSF materials under 1-sun and 100-sun AM 1.5 illumination condition. A conversion efficiency of 24.08 % and 27.22 % was achieved with InAlP FSF layer under 1-sun and 100-sun AM 1.5 spectrum, respectively. The results obtained from this study will contribute to a better understanding on the effect of FSF and BSF layers while obtaining the optimum FSF and BSF material for the GaAs-based photovoltaic cell.

Generally, waste heat is redundantly released into the surrounding by anthropogenic activities without strategized planning. Consequently, urban heat islands and global warming chronically increases over time. Thermophotovoltaic (TPV) systems can be potentially deployed to harvest waste heat and recuperate energy to tackle this global issue with supplementary generation of electrical energy. This paper presents a critical review on two dominant types of semiconductor materials, namely gallium antimonide (GaSb) and indium gallium arsenide (InGaAs), as the potential candidates for TPV cells. The advantages and drawbacks of non-epitaxy and epitaxy growth methods are well-discussed based on different semiconductor materials. In addition, this paper critically examines and summarizes the electrical cell performance of TPV cells made of GaSb, InGaAs and other narrow bandgap semiconductor materials. The cell conversion efficiency improvement in terms of structural design and architectural optimization are also comprehensively analyzed and discussed. Lastly, the practical applications, current issues and challenges of TPV cells are critically reviewed and concluded with recommendations for future research. The highlighted insights of this review will contribute to the increase in effort towards development of future TPV systems with improved cell conversion efficiency.

The significance of optimizing power intensity in a thermophotovoltaic system had spurred the efforts on exploiting thermophotovoltaic cells which are typically installed near to the heat source. Germanium with 0.66 eV bandgap is recommended and extensively employed to harvest infrared radiation up to $1.8\ \boldsymbol{\mu} \mathbf{m}$ . The integration of this material contributes to a cost-effective thermophotovoltaic system by capturing long wavelength under low blackbody temperature. Contrarily, the atmospheric perturbation between the heat source and the germanium thermophotovoltaic cells affects the intensity of incoming illumination, which alters the electrical performance of the cells. Nonetheless, the investigation of this issue is remained at the infancy stage and more characterization works are required to understand the influence of illumination intensity on the cell conversion efficiency. In this work, Silvaco TCAD software was used to characterize single Ge thermophotovoltaic cell under 2000 K blackbody radiation temperature by manipulating the illumination intensity. A conversion efficiency of 11.8% was achieved under higher illumination intensity of 2000 K due to the increase in the maximum voltage from 0.19 V to 0.42 V when compared to AM 1.5 illumination condition. The success of this work will contribute to the incorporation of understanding the effect of incident illumination intensity on the performance of Ge cell.