Temperature dependence of luminescence coupling effect in InGaP/GaAs/Ge triple junction solar cells

Abstract

Optimizing the luminescence coupling (LC) effect can reduce the current mismatch in multijunction solar cells (MJSCs), thereby enhancing their performance. In a previous work, the LC current collection was measured at room temperature. The temperature dependence of LC effect in InGaP/GaAs/Ge triple junction solar cells was observed by light J–V characteristics measurements and by laser beam-induced current mapping at operating temperatures between 18°C and 72°C. Results were analyzed using quasi-two-dimensional electro-optical model. At low operating temperatures, the photocurrent collection by LC effect has been found to be more dominant than the current collection due to bandgap reduction and thermal excitation of carriers. At 18°C and 72°C, when Ge bottom cell was made current limiting, the conversion efficiencies calculated were 6.68% and 0.01%, respectively. These findings show that the LC effect can contribute best to the MJSC performance when operated at the lowest temperature possible.