Strain-balanced quantum well concentrator cells from multiwafer production

Strain-balanced quantum well solar cells with 50 quantum well layers of In 0.11 GaAs in the intrinsic region of a GaAs p-i-n solar cell have been studied. Devices have been taken from different positions across 4” wafers from two manufacturing runs on a multi-wafer production reactor. Growth has been compared for devices with and without distributed Bragg reflectors (DBRs), and for devices with and without stepped p-region emitters. Device quantum efficiencies and dark currents have been modeled and compared to experimental data in order to predict efficiencies at 500 suns in an AM1.5D spectrum. Suppression of the radiative recombination component of the dark current has been observed in devices with DBRs, indicating the occurrence of photon recycling. A decrease in the Shockley injection component of the dark current has been found in devices with stepped p-region emitters, as minority carriers are deflected from the surface of the device. Good uniformity of performance has been observed in devices from across the wafer despite varying DBR position, and high device yields are to be expected during manufacture.