Effect of different tunnel diodes on the efficiency of multi-junction III-V solar cells

Abstract

InGaP/GaAs dual-junction solar cells with different tunnel diodes (TDs) grown on misoriented GaAs substrates are investigated. It is found that the solar cells with P⁺⁺-AlGaAs/N⁺⁺-GaAs TDs grown on 10° off GaAs substrates show a higher external quantum efficiency (EQE) but also generate a higher peak current density (J_peak) than the solar cells with P⁺⁺-GaAs/N⁺⁺-InGaP TDs grown on 10°off GaAs substrates. Furthermore, smooth surface (rms roughness: 1.54 Å) and sharp interface for the GaAs/Al_0.3Ga_0.7As TDs were obtained when the (100) tilted 10° off toward [111] GaAs substrate was used. The conversion efficiency of InGaP/GaAs dual-junction solar cell with N⁺⁺-GaAs/P⁺⁺-AlGaAs TD grown on the (100) tilted 10° off toward (111) GaAs substrate is close to 20%.