16.8%-Efficient n+/p GaAs Solar Cells on Si With High Short-Circuit Current Density
IEEE Journal of Photovoltaics(2019)
摘要
The highest efficiency heteroepitaxial GaAs solar cells on Si have historically been grown in the p
+
/n polarity, which was preferred due to the decreased sensitivity of open-circuit voltage in such cells to threading dislocations. The n
+
/p polarity also has potential advantages due to the higher mobility of electrons than holes in GaAs, and most multi-junction solar cells in the literature are grown in this polarity. Here, we demonstrate n
+
/p GaAs solar cells on Si with a certified AM1.5G efficiency of 16.8%, approaching the best certified efficiency of 18.1% for p
+
/n cells in the literature. The high efficiency of our n
+
/p cells is primarily due to the short-circuit current density of 26.5 mA/cm
2
, which is significantly higher than prior p
+
/n record cells. The strong carrier collection results from the use of a highly transparent AlInP window layer, thin n
+
emitter, and a relatively high minority electron diffusion length in the p
-
type base. The high quantum efficiency of these n
+
/p cells at wavelengths of 700–880 nm makes them promising for future triple-junction devices on Si, where the GaAs will serve as a middle sub-cell.
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关键词
Gallium arsenide,Silicon,Photovoltaic cells,Molecular beam epitaxial growth,Fans,Metals,Short-circuit currents
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