Graphene Transparent Conductive Electrodes for Highly Efficient Silicon Nanostructures-Based Hybrid Heterojunction Solar Cells

Abstract

In comparison to conventional metallic electrodes, graphene possesses superior properties in terms of higher optical transmittance, tunable work function, excellent stability in air, etc. Here, we demonstrate the use of graphene as transparent conductive electrodes for constructing highly efficient hybrid heterojunction solar cells based on nanostructured silicon, including silicon nanowire (SiNW) and silicon nanohole (SiNH) arrays. Poly(3-hexylthiophene) (P3HT) is adopted as hole transport layer in the hybrid heterojunction. It also offers a large offset between lowest unoccupied molecular orbital of the organic and the conduction band minimum of Si to reduce the electron recombination at graphene anode. The roles of graphene layer number, silicon surface modification, as well as P3HT layer thickness are systemically investigated. After sufficient device optimization, the devices based on graphene/P3HT/SiNW array and graphene/P3HT/SiNH array have achieved power conversion efficiencies of 9.94% and 10.34%, respectively. Considering the simple and low-cost solution processed capability for both graphene and P3HT layers, we believed that graphene/organic/silicon is a viable low-temperature technique for highly efficient silicon solar cell.