Low-intensity low-temperature (LILT) solar cells for deep space missions

The performance of low-intensity low-temperature (LILT) GaInP/GaInAs/Ge triple junction (TJ) solar cells grown by metal-organic vapor phase epitaxy (MOVPE) is investigated. Metamorphic (MM) epitaxy is achieved by varying the lattice constant between Ge and Ga0.94In0.06As in a compositionally graded buffer (CGB) layer. The relaxation of strain was measured to be about 96% by high-resolution X-ray diffraction (HRXRD). Threading dislocation density (TDD) estimated from cathodoluminescence (CL) images was about 6 x 10(4) /cm(2). The majority carrier barrier (MCB) height is reduced by reducing the doping concentration in the p-type base layer, resulting in an increase in the distance from the valence band to the Fermi energy level. The trends of temperature coefficient of Voc and Isc after radiation are opposite. Meanwhile, the degradation factor of power increases with temperature, which suggests increase of minority carrier lifetime caused by low temperature.

Automated summary

This study investigates the performance of low-intensity low-temperature (LILT) GaInP/GaInAs/Ge triple junction (TJ) solar cells grown by metal-organic vapor phase epitaxy (MOVPE). It is found that metamorphic (MM) epitaxy achieved by compositionally graded buffer (CGB) layer helps to reduce strain and improve the performance of solar cells.