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Concentrated photovoltaic (CPV) systems are one of the few technologies that can provide cost reduction while offering efficiency improvement. In this respect, the resistive losses are some of the main limiting factors, which restrict the efficiency improvement and the cost reduction at ultrahigh concentrations (UHCs). In this work, we propose and investigate new designs consisting of duplicated junction solar cells. The approach can resolve the issues related to the resistive losses. Simulation results, based on Shockley‐Queisser limit, demonstrate that the detrimental effects of series resistance losses in the degradation of efficiency at UHC factor can be mitigated with this strategy. The modeled structures are composed of multiple junctions of materials (GaInP, GaAs, and Ge), which are lattice‐matched to Ge or GaAs. These results illustrate the potential of duplicated junction designs for enhancing efficiency of III‐V solar cells under high concentrations, exceeding 1000 suns (under AM1.5D solar spectrum at 300 K). Finally, a relative cost calculation indicates that more than 30% of cost reduction can be achieved using these designs at UHCs.

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The quality and properties of epitaxial films are strongly determined by the reactor type and the precursor source phase. Such parameters can impose limitations in terms of background doping, interface sharpness, clustering, phase separation, and homogeneity. The authors have implemented a hybrid epitaxy technique that employs, simultaneously, vapor and solid sources as group III precursors. The system combines the high throughput and the versatility of gas sources as well as the high purity of solid sources. Using this technique, the authors successfully demonstrated epitaxial growth of Al 0.48 In 0.52 As and Ga 0.47 In 0.53 As layers on Fe-doped semi-insulating InP (001) substrates with interesting properties, compared with the epilayers grown by more standard techniques (chemical beam epitaxy, metal-organic chemical vapor deposition, and MBE). For AlInAs growth, trimethylindium and solid aluminum were used as In and Al precursors, respectively. In the case of GaInAs, triethylgallium and solid indium were used, respectively, as Ga and In precursors. Thermally cracked arsine (AsH 3) was used as an As (group V) precursor for both alloys. The AlInAs and GaInAs epilayers grown at a temperature of 500°C exhibited featureless surfaces with RMS roughness of 0.2 and 1 nm, respectively. Lattice mismatch is of 134 ppm, for AlInAs, and −96 ppm, for GaInAs, which were determined from high-resolution x-ray diffraction (HR-XRD) patterns and showed a large number of Pendellösung fringes, indicating a high crystalline quality. An FWHM of 18.5 arcs was obtained for GaInAs epilayers, while HR-XRD mapping of a full 2-in. wafer confirmed a viable lattice mismatch homogeneity (standard deviation of 0.026%) for as-grown layers. The authors observed room-temperature background doping values as low as 3 × 10 15 cm −3 , for AlInAs, and 1 × 10 15 cm −3 , for GaInAs. Analysis of the PL spectra at 20 K showed an FWHM of 8 meV, for AlInAs, and 9.7 meV, for GaInAs, demonstrating a very good optical quality of the epilayers. In addition, they have investigated the effects of the growth temperature and of the arsine pressure on epilayer properties. They also discuss the optimum conditions for the growth of high-quality Al 0.48 In 0.52 As and Ga 0.47 In 0.53 As layers on InP (001) substrates using this hybrid epitaxy technique.