Investigation of InGaP/Ga(In)As/Ge solar cells characteristics in the temperature range of 300 - 80 K

Abstract

Forward dark and load I - V characteristics of triple-junction GaInP/Ga(In)As/Ge solar cells (SCs) in the temperature range 300 - 80 K have been studied. At temperatures below 200 K, jumps of current and voltage in, respectively, dark and load characteristics were observed experimentally and attributed to the existence of a counter potential barrier formed by isotype heterolayers between the tunnel diode and the Ge p-n junction in the InGaP/Ga(In)As/Ge SC. An analysis of the forward dark characteristics of GaInP/Ga(In)As/Ge SCs, recorded at 80 K, enabled evaluation of the potential and real conversion efficiencies of incident sunlight. The influence exerted by the shape of the side mesa surface of GaInP/Ga(In)As/Ge SCs on the dominant current flow mechanisms was analysed. A method for single-step separate etching was suggested and studied. This method allows one to reduce surface leakage currents and raise the yield of suitable SCs with an efficiency greater than 35% at low sunlight concentrations (C = 10 - 100, T = 300 K). The suggested post-growth technology reduces the number of fabrication operations and the SC production cost and improves the reliability of the SC operation in a wide temperature range.