Axial p-n junction design and characterization for InP nanowire array solar cells

In this work, InP nanowire (NW) array solar cells with different axial p-i-n junction designs were investigated. The optical properties of the different NW structures were characterized through a series of microphotoluminescence measurements to extract important material parameters such as minority carrier lifetimes and internal quantum efficiencies. A glancing angle sputtering deposition technique has been developed to enable a direct visualization of the p-n junctions in the vertical array of InP NW solar cells (NWSCs) using electron beam-induced current (EBIC) technique. Based on EBIC and electrical simulation, it is found that the background doping in NWSC significantly affects the junction position. By modifying the junction design, the width and position of the p-n junction can be varied effectively. By employing a p-p ⁻ -n structure, a high junction position (>1 μm from the substrate) and wide depletion width have been achieved as confirmed by EBIC measurement. Moreover, the NW growth substrate does not show any influence on the device behavior due to the fully decoupled junction position, indicating a promising structural design for future development of high-performance, low-cost flexible NW devices.