Published by the AIP PublishingArticles you may be interested in Luminescence based series resistance mapping of III-V multijunction solar cells

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A number of important but little-investigated problems connected with III-V/Ge heterostructure in the GaInP/GaInAs/Ge multijunction solar cells grown by MOVPE are considered in the paper. The opportunity for successfully applying the combination of reflectance and reflectance anisotropy spectroscopy in situ methods for investigating III-V structure growth on a Ge substrate has been demonstrated. Photovoltaic properties of the III-V/Ge narrow-band subcell of the triple-junction solar cells have been investigated. It has been shown that there are excess currents in the Ge photovoltaic p-n junctions, and they have the tunneling or thermotunneling character. The values of the diode parameters for these current flow mechanisms have been determined. The potential barrier at the III-V/Ge interface was determined and the origin of this barrier formation during MOVPE heterogrowth was suggested.

Temperature photovoltaic dependencies have been measured at 90–350 K for a single-junction GaAs-based p-i-n solar cell and for a similar solar cell with imbedded in i-region In0.4Ga0.6As quantum objects. A theoretical approach for analyzing temperature dependencies of open circuit voltage has been proposed. A dethermalization of quantum objects has been observed at temperatures below 170 K, and the temperature of full dethermalization is estimated to be 80 K. It has been shown that dethermalized quantum objects are not involved in the photovoltaic process and may cause photocurrent losses, while, when thermalized, quantum objects give a photocurrent increment. It has been found that the energy difference between optic transitions in GaAs and in quantum objects is independent on temperature. Analysis of the temperature dependencies has allowed for the estimation of effective band gap energy of quantum objects which, at room temperature, was found to be 1.2 eV.