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Six-junction IIIa??V solar cells with 47.1% conversion efficiency under 143a??Suns concentration
摘要： Single-junction flat-plate terrestrial solar cells are fundamentally limited to about 30% solar-to-electricity conversion efficiency, but multiple junctions and concentrated light make much higher efficiencies practically achievable. Until now, four-junction III–V concentrator solar cells have demonstrated the highest solar conversion efficiencies. Here, we demonstrate 47.1% solar conversion efficiency using a monolithic, series-connected, six-junction inverted metamorphic structure operated under the direct spectrum at 143 Suns concentration. When tuned to the global spectrum, a variation of this structure achieves a 1-Sun global efficiency of 39.2%. Nearly optimal bandgaps for six junctions were fabricated using alloys of III–V semiconductors. To develop these junctions, it was necessary to minimize threading dislocations in lattice-mismatched III–V alloys, prevent phase segregation in metastable quaternary III–V alloys and understand dopant diffusion in complex structures. Further reduction of the series resistance within this structure could realistically enable efficiencies over 50%.
关键词： III–V solar cells,multijunction solar cells,concentrator solar cells,solar conversion efficiency
更新于2025-09-19 17:13:59
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1.73 eV AlGaAs/InGaP heterojunction solar cell grown by MBE with 18.7% efficiency
摘要： We report on AlGaAs-based heterojunction solar cells grown by solid source molecular beam epitaxy (MBE). We investigate InGaP and AlGaAs material quality and we demonstrate significant efficiency improvements by combining the best of each alloy: a thick p-AlGaAs base with tunable bandgap, and a thin 50 nm n-InGaP emitter separated by a thin intrinsic AlGaAs layer. We report a certified solar cell conversion efficiency of 18.7% with a 2-μm-thick AlGaAs layer and a bandgap of 1.73 eV, suitable for high efficiency Si-based tandem devices.
关键词： AlGaAs,MBE,InGaP,III-V solar cells,heterostructure
更新于2025-09-19 17:13:59
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Design and Demonstration of High-Efficiency Quantum Well Solar Cells Employing Thin Strained Superlattices
摘要： Nanostructured quantum well and quantum dot III–V solar cells provide a pathway to implement advanced single-junction photovoltaic device designs that can capture energy typically lost in traditional solar cells. To realize such high-efficiency single-junction devices, nanostructured device designs must be developed that maximize the open circuit voltage by minimizing both non-radiative and radiative components of the diode dark current. In this work, a study of the impact of barrier thickness in strained multiple quantum well solar cell structures suggests that apparent radiative efficiency is suppressed, and the collection efficiency is enhanced, at a quantum well barrier thickness of 4 nm or less. The observed changes in measured infrared external quantum efficiency and relative luminescence intensity in these thin barrier structures is attributed to increased wavefunction coupling and enhanced carrier transport across the quantum well region typically associated with the formation of a superlattice under a built-in field. In describing these effects, a high efficiency (>26% AM1.5) single-junction quantum well solar cell is demonstrated in a device structure employing both a strained superlattice and a heterojunction emitter.
关键词： quantum well solar cells,III–V solar cells,strained superlattices,photovoltaic devices,high-efficiency
更新于2025-09-16 10:30:52
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On the use of graphene to improve the performance of concentrator III‐V multijunction solar cells
摘要： Graphene has been intensively studied in photovoltaics focusing on emerging solar cells based on thin films, dye‐sensitized solar cells, quantum dots, nanowires, and so forth. However, the typical efficiency of these solar cells incorporating graphene is below 16%. Therefore, the photovoltaic potential of graphene has not yet been shown. In this work, the use of graphene for concentration applications on III‐V multijunction solar cells, which indeed are the solar cells with the highest efficiency, is demonstrated. First, a wide optoelectronic characterization of graphene layers is carried out. Then, the graphene layer is incorporated onto triple‐junction solar cells, which decreases their series resistance by 35% (relative), leading to an increase in fill factor of 4% (absolute) at concentrations of 1000 suns. Simultaneously, the optical absorption of graphene produces a relative short‐circuit current density decrease in the range of 0% to 1.8%. As a result, an absolute efficiency improvement close to 1% at concentrations of 1000 suns was achieved with respect to triple‐junction solar cells without graphene. The impact of incorporating one and two graphene monolayers is also evaluated.
关键词： III‐V solar cells,graphene,concentrator photovoltaics
更新于2025-09-12 10:27:22
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Pathways towards a 50% efficiency spectrum-splitting photovoltaic system: Application of built-in filters and generalization of concept
摘要： A UNSW team led by Martin Green achieved a landmark result in photovoltaics in 2014 when it demonstrated the first conversion of sunlight to electricity with efficiency above 40%. Besides this being one of the highest efficiencies ever reported, the work used a method readily accessible to the industry in that an external filter directed a portion of light normally wasted by commercial triple-junction solar cells to an additional silicon cell. Here, we propose two further developments that can make 50% conversion efficiency a realistic target. One potential development is to build filters into the rear of the cells themselves. Compared with the external filter, such internal filters can lead to an even higher efficiency because these internal filters can not only divide sunlight properly for individual cells as an external filter does, but also reflect the cells’ rear-emitted light back for reabsorption additionally. The other potential development is a generalisation of concept, where, for instance, the detached silicon cell may be replaced by another tandem cell that can better utilise the directed light unabsorbed by the first triple junction cell. This may also offer some flexibility in the filter design, since the spectrum shape of the directed light will no longer need to be rectangular. Detailed design principles will be discussed as is the potential for further efficiency improvement.
关键词： III-V solar cells,spectrum-splitting,luminescent coupling,filters,photovoltaics
更新于2025-09-12 10:27:22
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A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching
摘要： Thinning down the absorber layer of GaAs solar cells can reduce their cost and improve their radiation hardness, which is important for space applications. However, the lighttrapping schemes necessary to achieve high absorptance in these cells can be experimentally challenging or introduce various parasitic losses. In this work, a facile lighttrapping approach based on wet chemical etching is demonstrated. The rear‐side contact layer of ultrathin GaAs solar cells is wet‐chemically textured in between local Ohmic contact points using an NaOH‐based etchant. The resulting contact layer morphology is characterized using atomic force microscopy and scanning electron miscroscopy. High broadband diffuse reflectance and haze factors are measured on bare and Ag‐coated textured contact layers. The textured contact layer is successfully integrated as a diffusive rear mirror in thin‐film solar cells comprising a 300‐nm GaAs absorber and Ag rear contact. Consistent increases in short‐circuit current density (JSC) of approximately 3 mA cm?2 (15%) are achieved in the textured cells, while the open‐circuit voltages and fill factors do not suffer from the textured rear mirror. The best cell achieves a JSC of 24.8 mA cm?2 and a power conversion efficiency of 21.4%. The textured rear mirror enhances outcoupling of luminescence at open circuit, leading to a strong increase in the external luminescent efficiency.
关键词： ultra‐thin GaAs,wet etching,textured III‐V solar cells,light trapping,luminescence outcoupling
更新于2025-09-12 10:27:22
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Optical Characterization of III-V Multijunction Solar Cells for Temperature-Independent Band Gap Features
摘要： A recently developed method to characterize the band gap energies of III-V optosemiconductors was utilized to determine temperature-invariant band gap features of multijunction solar cells. The method is based on measuring electroluminescent spectra of the solar cells at different temperatures. The normalized spectra reveal temperature-invariant energy values of the different junctions which are further converted to band gap energies. The method utilization requires a calibrated spectroradiometer and a temperature controlled mounting base for the solar cell under test, however, no knowledge about the absolute temperature of the cell under measurement. The method was tested on GaAs and GaInP solar cells that consist of single and dual junctions. The band gap energies were also derived from spectral response measurements. The differences of the determined band gap energies from the literature values were smaller than 1.1%. Compared with other band gap determination methods, the developed method yields temperature-invariant band gap characteristics; with a known uncertainty, that separated the different junctions in a multijunction device without individual biasing for the different junctions. In addition, a temperature-independent characterization parameter ensures that the operating conditions of the device under test do not affect the results.
关键词： III-V solar cells,light-emitting diode (LED),spectral response,temperature,Band gap
更新于2025-09-12 10:27:22
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III‐V//Si multijunction solar cells with 30% efficiency using smart stack technology with Pd nanoparticle array
摘要： Multijunction (MJ) solar cells achieve very high efficiencies by effectively utilizing the entire solar spectrum. Previously, we constructed a III‐V//Si MJ solar cell using the smart stack technology, a unique mechanical stacking technology with Pd nanoparticle array. In this study, we fabricated an InGaP/AlGaAs//Si three‐junction solar cell with an efficiency of 30.8% under AM 1.5G solar spectrum illumination. This efficiency is considerably higher than our previous result (25.1%). The superior performance was achieved by optimizing the structure of the upper GaAs‐based cell and employing a tunnel oxide passivated contact Si cell. Furthermore, we examined the low solar concentration performance of the device and obtained a maximum efficiency of 32.6% at 5.5 suns. This performance is sufficient for realistic low concentration photovoltaic applications (below 10 suns). In addition, we characterize the reliability of the InGaP/AlGaAs//Si three‐junction solar cell with a damp heat test (85 °C and 85% humidity for 1000 h). It was confirmed that our solar cells have high long‐term stability under severe conditions. The results demonstrate the potential of GaAs//Si MJ solar cells as next‐generation photovoltaic cells and the effectiveness of smart stack technology in fabricating multijunction cells.
关键词： III‐V solar cells,photovoltaic concentrator,mechanical stack,multijunction solar cells,silicon solar cells
更新于2025-09-11 14:15:04