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

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 (Jpeak) 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/Al0.3Ga0.7As 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%.