TUTCRIS - Tampereen teknillinen yliopisto


Lattice‐matched four‐junction tandem solar cell including two dilute nitride bottom junctions



JulkaisuProgress in Photovoltaics: Research and Applications
DOI - pysyväislinkit
TilaJulkaistu - 10 joulukuuta 2018
OKM-julkaisutyyppiA1 Alkuperäisartikkeli


Monolithic four‐junction solar cells incorporating two dilute nitride (GaInNAsSb) bottom junctions are reported. The dilute nitride junctions have band gaps of 0.9 and 1.2 eV, while the top junctions have band gaps of 1.4 and 1.9 eV. By using experimental‐based parametrization, it was estimated that the four‐junction solar cell could theoretically exhibit efficiency levels of 34.7% at one sun, 43.2% at 100 suns, and 46.4% at 1000 suns for AM1.5D illumination. The most challenging subcell in terms of fabrication is the GaInNAsSb bottom junction with 0.9 eV band gap. For this subcell, a background doping level down to 5 × 1014 cm−3 and a high charge carrier lifetime up to 2 to 4 nanoseconds are reported, which reflects high values for current and voltage. An experimental AlGaAs/GaAs/GaInNAsSb/GaInNAsSb solar cell structure was fabricated by molecular beam epitaxy. At one‐sun AM1.5D illumination, the experimental cell exhibited an efficiency of 25%, an average quantum efficiency of 91%, and an open circuit voltage, which is about 87% of the estimated potential. The cell exhibited maximum efficiency of 37% at 100‐sun concentration.



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