High-performance Core/Shell InGaN/GaN Radial Multi-quantum-well Nanowire Solar Cells Non-catalytically Grown on Si Wafers

Abstract

We report photovoltaic properties of solar cells made of core/shell InGaN/GaN multi quantum wells (MQWs)-nanowire (NW) arrays, vertically-grown through oxide-template hole patterns from n-GaN thin films on n-type Si wafers. Detailed structural properties are analyzed for two types of the solar cells containing defect-free or defective active layer (MQWs) by high-resolution transmission electron microscopy. Photocurrent and external quantum efficiency are greatly enhanced in the defect-free solar cells due to better charge collection/transport. Maximum power conversion efficiency (PCE) of ~ 4.22%, highest ever known for the similar structures, is achieved with ~ 1.11 V open-circuit voltage, ~ 6.80 mA/cm2 short-circuit current density, and ~ 0.56 fill factor in the defect-free solar cells. These results suggest that the well-defined active layer in InGaN/GaN MQWs-NWs solar cells is crucial for enhancing their PCE and further explain why the PCE of the solar cells employing similar structures in the previous reports were comparatively low.