Single junction InGaP/GaAs solar cells displaying high efficiency and record high open‐circuit voltage values have been grown by metal–organic chemical vapor deposition on Ge/graded SiGe/Si substrates. Open‐circuit voltages of 980 mV under AM0 conditions have been verified to result from a single GaAs junction, with no evidence of Ge‐related sub‐cell photoresponse. AM0 efficiencies close to 16% have been measured for a large number of small‐area cells, the performance of which is limited by non‐fundamental current losses due to significant surface reflection resulting from> 10% front‐surface metal coverage and wafer handling during the growth sequence for these prototype cells. It is shown that at the material quality currently achieved for GaAs grown on Ge/SiGe/Si substrates, namely a 10 ns minority‐carrier lifetime that results from complete elimination of anti‐phase domains, and maintaining a threading dislocation density of ∼8 × 105 cm−2, 19–20% AM0 single‐junction GaAs cells are imminent. Experiments show that the high performance is not degraded for larger‐area cells, with identical open‐circuit voltages and higher short‐circuit current (due to reduced front metal coverage) values being demonstrated, indicating that large‐area scaling is possible in the near term. Comparison with a simple model indicates that the voltage output of these GaAs‐on‐Si cells follows the ideal behavior expected for lattice‐mismatched devices, demonstrating that unaccounted‐for defects and issues that have plagued other methods to epitaxially integrate III–V cells with Si are resolved by using SiGe buffers and proper GaAs nucleation methods. These early results already show the enormous and realistic potential of the virtual SiGe substrate approach for generating high‐efficiency, lightweight and strong III–V solar cells. Copyright © 2002 John Wiley & Sons, Ltd.

Autonomous systems are increasingly used to provide situational awareness and long-term environment monitoring. Photovoltaics (PV) are favored as a long-endurance power source for many of these applications. To date, the use of PV is limited to space and terrestrial (dry-land) installations. The need for a persistent power source also exists for underwater (UW) systems, which currently rely on surface PV arrays or batteries. In this paper, we demonstrate that high-bandgap-InGaP solar cells can provide useful power UW.

Metal halide perovskite solar cells have progressed rapidly over the past decade, providing an exceptional opportunity for space photovoltaic (PV) power applications. However, the solar cells to be used for space power have to demonstrate a stable operation under extreme conditions, particularly concerning harsh radiations. In contrast to previously reported superior stability of low PV performance perovskite solar cells against high-energy radiation, we investigate the effects of high-energy electron beam irradiation on the degradation of perovskite solar cells with a high-power conversion efficiency exceeding 20%. We find very high remaining factors of >87.7% in the open-circuit voltage (V OC ) and >93.5% in the fill factor (FF) and a significantly decreased short-circuit current density (J SC ) after the exposure to high-fluence electron irradiations of 10 15 e/cm 2 . The pronounced loss of J SC is due to the decreasing transmittance of the soda-lime glass substrate and the partial decomposition of the perovskite absorber layers. The irradiated cells retained superior remaining factors in both V OC and FF, demonstrating a superior tolerance of perovskite solar cells after the exposure to the electron irradiation. These results show that perovskite solar cells hold great potential for space PV power applications if stable perovskite compositions and space-suitable substrates are employed.

conversion efficiency. Devices comprising these alloys (and, in some cases, the group IV element, germanium) have held the world record for conversion efficiency under concentrated sunlight for more than the last thirty years with steady increases in efficiency year-on-year. [2] Efficiency improvements result from many aspects of MJSC design, but among the most important of these are improving the distribution of light between the subcells of the MJSC, increasing the number of subcells, and increasing the fraction of the solar spectrum being captured.The ideal MJSC would harvest the entire solar spectrum extending into the midinfrared wavelength range using a very large number of closely spaced bandgaps, and the theoretical upper-limit of conversion efficiency is ≈86%, assuming full solar concentration of 45900 suns. [3] The Earth's atmosphere filters the solar spectrum, such that ≈99% of the power contained in the direct-beam airmass 1.5 (AM1.5D) reference spectrum is contained within the spectral band covering 300-2500 nm. This filtering impacts the optimal bandgaps for MJSCs, and recent calculations showed that the optimum lowest energy bandgap for practical MJSC solutions with 4-7 junctions is ≈0.5 eV (2500 nm). [4] These calculations assume more realistic device performance than the idealized, detailed-balance models, [5] and a more practical solar concentration of 1000X, which yields an efficiency projection of 54.6% for a 7 junction (7J) device. Therefore, to achieve virtually full spectrum energy harvesting of the direct-beam component of the terrestrial spectrum, 0.5 eV is the best practical target for the lowest bandgap absorber in an advanced MJSCs with four or more junctions. It should be noted that concentrator photovoltaic (CPV) solutions are typically unable to capture the diffuse portion of the irradiation, which can be a significant fraction of the global irradiation in terrestrial applications. However, recent advancements in hybrid approaches which combine CPV cells with larger area solar cells on the module back-plane to capture diffuse light [6] offer a potential route to even higher efficiency with respect to the total global irradiation incident on a photovoltaic module.No single III-V or group IV substrate offers direct-bandgap, lattice-matched (LM) III-V alloys which span the entire spectral range at favorable bandgap intervals for producing MJSCs In this work, a multijunction solar cell is developed on a GaSb substrate that can efficiently convert the long-wavelength photons typically lost in a multijunction solar cell into electricity. A combination of modeling and experimental device development is used to optimize the performance of a dual junction GaSb/InGaAsSb concentrator solar cell. Using transfer printing, a commercially available GaAs-based triple junction cell is stacked mechanically with the GaSb-based materials to create a four-terminal, five junction cell with a spectral response range covering the region containing >99% of the available direct-beam power from the Sun reachi...

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