Efficiency enhancement of graphene/silicon-pillar-array solar cells by HNO3 and PEDOT-PSS

A single-layer graphene film was grown on copper foil by chemical vapor deposition and transferred onto a silicon-pillar-array (SPA) substrate to make a Schottky junction solar cell. The SPA substrate was specifically designed to suppress reflectance and enhance light absorption. The energy conversion efficiency of the prepared graphene/SPA solar cells achieved a maximum of 2.90% with a junction area of 0.09 cm(2). HNO3 was employed to dope the graphene in the solar cells, and the time dependence of HNO3 treatment on the cell performance was studied. Poly(3,4-ethylenedioxythiophene) polystyrenesulfonic acid (PEDOT-PSS) was also introduced in graphene/SPA solar cells by spin coating on top of the graphene film, and its modification on the cell performance was characterized. The results show that both HNO3 and the PEDOT-PSS film could enhance the energy conversion efficiency of graphene/SPA solar cells.