Triple-junction GaInP/GaAs/Ge Solar cells with an AZO transparent electrode and ZnO nanowires

In this paper, the fabrication of GaInP/GaAs/Ge triple-junction (TJ) solar cells with an Al-doped ZnO (AZO) transparent electrode and a ZnO nanowire (NW) antireflection (AR) layer is reported. It was found that ZnO NWs/AZO could provide a smaller reflectance, as compared with AZO and MgF₂/Ta ₂O₅. By inserting a 4-nm-thick AuGeNi between AZO and n⁺-AlInP, it was found that the rectifying contact could be transformed into an ohmic contact with a specific contact resistance of 1.02 × 10^-5 Ω·cm². Furthermore, it was found that the ZnO NWs/ZnO used in this study could enhance the conversion efficiency of TJ solar cells from 21.91% to 28.16%, which corresponds to a 25.4% relative enhancement in the conversion efficiency.