Search Results (37)

Raising the efficiency of triple-junction cells such as (GaInP/GaInAs/Ge) is an important goal for designing high-concentration photovoltaic systems. This purpose can be achieved by facing cell obstacles and acting on their configurations to sustain under highly concentrated sunlight and high operating temperatures. In this paper, a prediction performance study of triple-junction solar cells with four types of structures is proposed under variable conditions. The results show that the series structure is well-validated with experimental data under standard test conditions and is presented against those under variable conditions. Then, the triple-junction cells are compared and discussed in terms of photovoltaic cell open circuit voltage, photovoltaic cell electrical efficiency, fill factor, and temperature coefficients. Consequently, the results show that the cells can be separated into two categories that are useful for Low Concentration Systems and High Concentration Systems. The Low Concentration Systems present high efficiency at 20 suns. For the High Concentration Systems, the Hybrid 2 type demonstrates an optimal efficiency of 38.48% at 118 suns with a high FF (0.873) and shows a lower temperature coefficient than the series type. So, Hybrid 2 presents a good candidate for high-concentration systems with a performance better than the conventional triple-junction cells. Full article

This study presents the theoretical design and evaluation of a triple-junction polymer solar cell architecture, incorporating oligomers of PDCBT, PPDT2FBT, and PDPP3T as donor materials and PC₇₁BM as the electron acceptor. Using density functional theory (DFT) simulations and time-dependent DFT (TD-DFT) methods, the investigation covers essential photovoltaic parameters, including molecular geometries, UV-Vis spectra, and charge transport properties. The device is structured to maximize solar energy absorption across the spectrum, featuring front, middle, and back junctions with band gaps of 1.9 eV, 1.63 eV, and 1.33 eV, respectively. Each layer targets different regions of the solar spectrum, optimizing light harvesting and charge separation. This innovative multi-junction design offers a promising pathway to enhanced power conversion efficiencies in polymer solar cells, advancing the integration of renewable energy technologies. Full article

A novel prototype based on the combination of a multi-junction, high-efficiency photovoltaic (PV) module and a supercapacitor (SC) able to self-power a wireless sensor node (WSN) for outdoor air quality monitoring has been developed and tested. A PV module with about an 8 cm² active area made of eight GaAs-based triple-junction solar cells with a nominal 29% efficiency was assembled and characterized under terrestrial clear-sky conditions. Energy is stored in a 4000 F/4.2 V supercapacitor with high energy capacity and a virtually infinite lifetime (10⁴ cycles). The node power consumption was tailored to the typical power consumption of miniaturized, low-consumption NDIR CO₂ sensors relying on an LED as the IR source. The charge/discharge cycles of the supercapacitor connected to the triple-junction PV module were measured under illumination with a Sun Simulator device at selected radiation intensities and different node duty cycles. Tests of the miniaturized prototype in different illumination conditions outdoors were carried out. A model was developed from the test outcomes to predict the maximum number of sensor samplings and data transmissions tolerated by the node, thus optimizing the WSN operating conditions to ensure its self-powering for years of outdoor deployment. The results show the self-powering ability of the WSN node over different insolation periods throughout the year, demonstrating its operation for a virtually unlimited lifetime without the need for battery substitution. Full article

To study the physical property effects of the laser on GaInP/GaAs/Ge solar cells and their sub-cell layers, a pulsed laser with a wavelength of 532 nm was used to irradiate the solar cells under various energy conditions. The working performance of the cell was measured with a source meter. The electroluminescence (EL) characteristics were assessed using an ordinary and an infrared camera. Based on the detailed balance theory, in the voltage characteristics of an ideal pristine cell, the GaInP layer made the most significant voltage contribution, followed by the GaAs layer, with the Ge layer contributing the least. When a bias voltage was applied to the pristine cell, the top GaInP cell emitted red light at 670 nm, the middle GaAs cell emitted near-infrared light at 926 nm, and the bottom Ge cell emitted infrared light at 1852 nm. In the experiment, the 532 nm laser wavelength within the response spectrum bands of the GaInP layer and the laser passed through the glass cover slip and directly interacted with the GaInP layer. The experimental results indicated that the GaInP layer first exhibited different degrees of damage under laser irradiation, and the cell voltage was substantially attenuated. The GaInP/GaAs/Ge solar cell showed a decrease in electrical and light emission characteristics. As the laser energy increased, the cell’s damage intensified, gradually leading to a loss of photoelectric conversion capability, the near-complete disappearance of red light emission, and a gradual degradation of near-infrared emission properties. The EL imaging revealed varying damage states across the triple-junction gallium arsenide solar cell’s sub-cells. Full article

Optical wireless power transmission systems are attracting attention as a new power transmission technology because they can supply power wirelessly over long distances. In this study, we investigated InGaP/InGaAs/Ge triple-junction solar cells simultaneously irradiated with three laser beams with wavelengths of 635 nm, 850 nm, and 1550 nm to improve photoelectric conversion efficiency. As a result, a photoelectric conversion efficiency of 45.0% was obtained under three laser irradiations with a total incident laser power of 1.77 W/cm². The results showed the possibility of a high-efficiency optical wireless power transmission system by simultaneously irradiating laser beams with different wavelengths onto multi-junction solar cells, which could be installed in automobiles as a new system that complements solar power generation for daylighting. Full article

The solar energy market is predicted to be shared between Si solar cells and third-generation photovoltaics in the future. Perovskite solar cells (PSCs) show the greatest potential to capture a share there as a single junction or in tandem with silicon. Researchers worldwide are looking to optimize the composition of the perovskite film to achieve an optimal bandgap, performance, and stability. Traditional perovskites have a mixture of formamidinium and methyl ammonium as the A-site cation in their ABX₃ structure. However, in recent times, the use of cesium and rubidium has become popular for making highly efficient PSCs. A thorough analysis of the performance and stability of double-, triple-, and quadruple-cation PSCs under different environmental conditions was performed in this study. The performance of the device and the films was analyzed by electrical measurements (J–V, dark J–V, EQE), scanning electron microscopy, atomic force microscopy, photoluminescence, and X-ray diffraction. The quadruple-cation device with the formula Cs_0.07Rb_0.03FA_0.77MA_0.13PbI_2.8Br_0.2 showed the highest power conversion efficiency (PCE) of 21.7%. However, this device had the least stability under all conditions. The triple-cation device with the formula Cs_0.1FA_0.6MA_0.3PbI_2.8Br_0.2, with a slightly lower PCE (21.2%), was considerably more stable, resulting in about 30% more energy harvested than that using the other two devices during their life cycle. Full article

Improvement of triple-junction (3J) III-V/Ge solar cells efficiency is hindered by the low current produced by the top and middle cells relative to the bottom cell (Ge). This can be explained by the difficulty of characterizing, on an individual basis, the subcells. We investigate the fabrication process of multi-terminal multi-junction solar cells (MTMJSC) and its potential as a promising architecture to independently characterize subcells of multi-junction solar cells. Here, we study monolithic triple-junction solar cells, with an InGaP top cell, an InGaAs middle cell and a Ge bottom cell interconnected by tunnel junctions. We demonstrate a fabrication process for MTMJSC on commercial wafers for characterization applications purposes. I-V measurements, under illumination, of two-terminals and MTMJSC were compared to validate that the MTMJSC fabrication process does not degrade the cells’ performance. The dark current of each subcell was also measured and an ideal-diode model used to determine the subcells electrical parameters. The results suggest a method to measure the relative absorption and the opto-electrical couplings between the subcells unambiguously, through EQE and electroluminescence measurements, based on basic micro-fabrication processes. Full article

The optics is the component that most affects the concentrating photovoltaic (CPV) system performance, depending above all on the concentration factor and optical efficiency. Hence, a basic aspect is the concentrated solar flux measure on the receiving area, the evaluation of which is principally realized by indirect measurement methods. First, a literature review on indirect and direct methods used for the evaluation of concentrated solar flux and optical parameters is presented in this paper. The experimental measurement procedure, which is able to evaluate the optical parameters and concentrated solar flux in CPV systems, is also presented. The main steps of this procedure are represented by experimental system setup, sensor selection for concentrated solar flux estimation, identification of all the factors affecting optical performances, and development of an experimental campaign and output analysis. In particular, the optical characterization results of a CPV system are obtained by means of in-depth experimental analysis using Triple-Junction (TJ) solar cells with areas of 5.5 × 5.5 mm² and 10 × 10 mm². Three different setups have been analyzed related to primary and secondary optics composition. The main aim of this paper is the determination of a direct measuring technique, rarely adopted in literature in comparison to the established techniques, that is able to evaluate experimentally the optical parameter values and that can be standardized for other CPV systems. In particular, equations that link the optical concentration factor (C) and efficiency (η_opt) with focal distance (h) represent the fundamental results. They can be used for similar point-focus configurations presenting the same TJ cell size and ranges of C, η_opt and h. Finally, the experimental results of the direct method are compared with those of an indirect method adopting the same CPV system and operational conditions. Full article

We report chemically tunable n-type titanium oxides using ethanolamine as a nitrogen dopant source. As the amount of ethanolamine added to the titanium oxide precursor during synthesis increases, the Fermi level of the resulting titanium oxides (ethanolamine-incorporated titanium oxides) significantly changes from −4.9 eV to −4.3 eV, and their free charge carrier densities are enhanced by two orders of magnitudes, reaching up to 5 × 10¹⁸ cm⁻³. Unexpectedly, a basic ethanolamine reinforces not only the n-type properties of titanium oxides, but also their basicity, which facilitates acid–base ionic junctions in contact with acidic materials. The enhanced charge carrier density and basicity of the chemically tuned titanium oxides enable multi-junction solar cells to have interconnecting junctions consisting of basic n-type titanium oxides and acidic p-type PEDOT:PSS to gain high open-circuit voltages of 1.44 V and 2.25 V from tandem and triple architectures, respectively. Full article

Improving the performances and reducing costs of III-V multijunction solar cells are crucial in aerospatial energy systems and in terrestrial concentrator modules. We attempted to achieve both objectives by implementing non-ohmic metal/semiconductor interface contacts on the front surface of III-V/Ge triple-junction solar cells. We demonstrate the feasibility of this concept for this type of solar cell by a simple evaporation of Al only either on the GaAs contact layer or the AlInP window. The best results were obtained when sulfur passivation by (NH₄)2S_x was conducted on the GaAs contact layer. This allowed for a reduction in reverse saturation dark current density by one order of magnitude and a slight increase in V${}_{oc}$ of almost 20 mV under 1 sun illumination relative to a reference device with Pd/Ge/Ti/Pd ohmic contacts. However, poor performances were observed at first under concentrated sunlight. Further annealing the solar cells with Al front metallization resulted in the reduction of V${}_{oc}$ to the same level as the reference solar cell but allowed for good performances under high illumination. Indeed, an efficiency over 34% was observed at 500 suns light intensity both for Al and Pd/Ge/Ti/Pd contacted solar cells. Full article

Based on the new high-modulus carbon fiber CCM40J-6k, which is the critical raw material of a solar panel, the molding process of a mesh face sheet combined with epoxy resin, the overall mechanical performance of a mesh face sheet combined with aluminum honeycomb, the compatibility with polyimide insulation film + solar cell circuit, and the space environment adaptability must pass a test verification and assessment as the premise for large-scale orbit applications. Therefore, based on the traditional carbon fiber M40JB-6k as a reference, a systematic verification project was conducted to apply the CCM40J-6k carbon fiber composite at the process, component, and assembly levels. Six aspects of testing and verifying items were conducted, including mechanical properties under room temperature and thermal shock conditions, bonding force of mesh nodes, comparison of the adaptability of domestic and imported carbon fiber substrates to high–low temperature alternation, the ability of domestic carbon fiber substrates to adapt to the thermal environment after laying solar cell circuits, and in-orbit lifespan of solar panels. Based on the verification results, the mechanical properties of the substrate are the same as those of the imported M40JB-6k, and the actual molding process for M40JB-6k can be utilized. Sample pieces of the substrates can withstand the thermal shock and thermal cycling tests. The bending stiffness of the sample pieces before and after the tests is 3.5%~9.6% higher, and the bending strength is 4.2%~7.2% lower. The tensile strength of mesh nodes made of domestic carbon fiber is 18.9% higher than that of mesh nodes made of imported carbon fiber. The CCM40J-6k substrate is similar to triple-junction GaAs solar cells. The change rates of the open-circuit voltage and the short-circuit current of solar panels based on domestic carbon fiber after fatigue thermal cycling with 2070 cycles are 0.55% and 0.24%, respectively. The above results indicate that the comprehensive performance of the domestic carbon fiber CCM40J-6k meets the requirements and can be applied to solar panels for solar arrays. Full article

A lattice matched triple junction solar cell (TJSC) structure with a GaAs_0.58 P_0.42 top cell and bandgap tunable GaN_xAs_1-x-zP_z middle and bottom cells on virtual SiGe substrate is proposed in this study. SiGe/Si substrate is preferred as it is a low-cost substrate and because it provides a lattice constant at which bandgap tunable dilute nitride materials that are appropriate for highly efficient multijunction solar cells can be obtained. By changing the nitrogen content in GaN_xAs_1-x-zP_z, the bandgap of the middle and bottom subcells is adjusted to the optimum values. The bandgap of the top cell is constant at 1.95 eV. Three models with different values of surface recombination velocities and Shockley–Read–Hall recombination lifetimes are applied to the presented TJSC structure. Peak efficiencies of 48.9%, 40.6% and 33.7% are achieved at E_G2 = 1.45 eV and E_G3 = 1.04 eV for Model 1, E_G2 = 1.45 eV and E_G3 = 1.15 eV for Model 2, and E_G2 = 1.5 eV and E_G3 = 1.17 eV for Model 3, respectively. A fourth bandgap adjustable GaN_xAs_1-x-zP_z junction is inserted into the system and a significant improvement is obtained under high sun concentration for Models 1 and 2. The presented original results are very promising because the variable bandgaps provide very efficient absorption of incoming spectrum. Full article

Highly concentrated triple-junction solar cells (HCTJSCs) are cells that have diverse applications for power generation. Their electrical efficiency is almost 45%, which may be increased to 50% by the end of the year 2030. Despite their overwhelming ability to generate power, their efficiency is lower when utilized in a concentrated manner, which introduces a high-temperature surge, leading to a sudden drop in output power. In this study, the efficiency of a 10 mm × 10 mm multijunction solar cell (MJSC) was increased to almost 42% under the climatic conditions in Lahore, Pakistan. Active cooling was selected, where SiO₂–water- and Al₂O₃–water-based nanofluids with varying volume fractions, ranging from 5% to 15% by volume, were used with a 0.001 kg/s mass flow rate. In addition, two- and three-layer microchannel heat sinks (MCHSs) with squared microchannels were designed to perform thermal management. Regarding the concentration ratio, 1500 suns were considered for 15 August at noon, with 805 W/m² and 110 W/m² direct and indirect radiation, respectively. A complete model including a triple-junction solar cell and allied assemblies was modeled in Solidworks software, followed by temperature profile generation in steady-state thermal analyses (SSTA). Thereafter, a coupling of SSTA and Ansys Fluent was made, in combination with the thermal management of the entire model, where the temperature of the TJSC was found to be 991 °C without active cooling, resulting in a decrease in electrical output. At 0.001 kg/s, the optimum average surface temperature (44.5 °C), electrical efficiency (41.97%), and temperature uniformity (16.47 °C) were achieved in the of MJSC with SiO₂–water nanofluid with three layers of MCHS at a 15% volume fraction. Furthermore, the average outlet temperature of the Al₂O₃–water nanofluid at all volume fractions was high, between 29.53 °C and 31.83 °C, using the two-layer configuration. For the three-layer arrangement, the input and output temperatures of the working fluid were found to be the same at 25 °C. Full article

The shortening of the minority carrier lifetime is the main reason for the degradation of the electrical performance of solar cells; therefore, it is particularly important to evaluate the minority carrier lifetime of inverted metamorphic triple junction (IMM3J) GaInP/GaAs/InGaAs solar cells. We evaluate the minority carrier lifetime of each subcell of IMM3J solar cells before and after 2 MeV proton irradiation by the electroluminescence (EL) method. Before proton irradiation, the minority carrier lifetimes of the GaInP, GaAs, and InGaAs subcells were 6.99 × 10⁻⁹ s, 3.09 × 10⁻⁸ s, and 2.31 × 10⁻⁸ s, respectively. After proton irradiation, the minority carrier lifetime of GaInP, GaAs, and InGaAs subcells degraded significantly. When the proton fluence was 2 × 10¹² cm⁻², the minority carrier lifetimes of the GaInP, GaAs, and InGaAs subcells degraded to 1.63 × 10⁻¹⁰ s, 1.56 × 10⁻¹¹ s, and 1.65 × 10⁻¹⁰ s, respectively. These results provide a reference for predicting the degradation of the short-circuit current and open-circuit voltage of each subcell. Full article

Epitaxial growth of III–V materials on Si is a promising approach for large-scale, relatively low-cost, and high-efficiency Si-based multi-junction solar cells. Several micron-thick III–V compositionally graded buffers are typically grown to reduce the high threading dislocation density that arises due to the lattice mismatch between III–V and Si. Here, we show that optically transparent n-In_0.1Al_0.9As/n-GaAs strained layer superlattice dislocation filter layers can be used to reduce the threading dislocation density in the GaAs buffer on Si while maintaining the GaAs buffer thickness below 2 μm. Electron channeling contrast imaging measurements on the 2 μm n-GaAs/Si template revealed a threading dislocation density of 6 × 10⁷ cm⁻² owing to the effective n-In_0.1Al_0.9As/n-GaAs superlattice filter layers. Our GaAs/Si tandem cell showed an open-circuit voltage of 1.28 V, Si bottom cell limited short-circuit current of 7.2 mA/cm², and an efficiency of 7.5%. This result paves the way toward monolithically integrated triple-junction solar cells on Si substrates. Full article