Connecting wire-based solar cells without any transparent conducting electrode

In order to reduce substrate costs and increase light absorption, solar cells based on semiconductor wire arrays are currently being actively studied. Whether built with Si, InP or other semiconductor materials, wire-based cells invariably use a transparent conductive coating for one of the electrodes, which complicates the processing and does not contribute to the reduction of the overall cost of the cell. Here, we propose a totally novel connection process, where the transparent conductive electrode is replaced with an array of in situ grown metallic nanowires. During their growth, these metallic nanowires randomly connect to core-shell p-i-n Si wires previously synthesized by chemical vapor deposition. We demonstrate the feasibility of this new random connection concept by using a coplanar solar cell design with interdigitated base and emitter contacts. We obtain a high fill factor of similar to 74% and efficiencies of 4.5% with only 33% of the surface covered by p-i-n Si wires.