2-TERMINAL MONOLITHIC IN0.5GA0.5P GAAS TANDEM SOLAR-CELLS WITH A HIGHCONVERSION EFFICIENCY OF OVER 30-PERCENT/

A world-record efficiency of 30.28% has been attained for two-terminal monolithic In0.5Ga0.5P/GaAs tandem solar cells under one-sun air-mass 1.5 global illumination. The cell area has a practical size of a cm(2 ). At first, high efficiency In0.5Ga0.5P single junction cells had bee n developed by improving tile minority carrier lifetime. Second, the G alls single junction cells had been investigated to obtain higher open -circuit voltage, Third; the tandem cell performance had been improved by using an InGaP tunnel junction with AlInP barriers which constitut e a double-hetero structure and increase the peak current of the tunne l junction. in addition, the AlInP barrier located beneath the InGaP t op cell have been found to be effective for reflecting minority carrie rs in the top cell and for suppressing the diffusion of zinc from the highly doped tunnel junction toward the top cell during epitaxial grow th.