Direct Growth of Graphene Nanowalls on Inverted Pyramid Silicon for Schottky Junction Solar Cells

In this work, we develop a radio-frequency plasma-enhanced horizontal tube furnace deposition system to directly grow graphene nanowalls (GNWs) on inverted pyramid (IP) silicon without using catalysts and fabricate GNWs/IP silicon Schottky junction solar cells. The morphology, microstructure, and optical and electrical properties of the synthesized GNWs and IP silicon are investigated. It is shown that GNWs are distributed on the whole surface of the IP silicon and feature an outstanding electrode network. Moreover, in situ optical emission spectroscopy measurement is carried out to investigate the growth process and chemical reaction mechanism of GNWs under the plasma-based process. Due to the excellent light-trapping structure of IP silicon and outstanding electrode network of GNWs, the photovoltaic conversion efficiency (PCE) of the pristine GNWs/IP Si solar cells can reach up to 4.05% via controlling the growth time of GNWs. A PCE of 7.2% can be achieved for the GNWs/IP Si solar cells by combining HNO3 p-doping treatment and spin-coating TiO2 as an antireflective layer. This work plays a vital role in the development of a simple and advanced process for the realization of high-efficiency graphene-based solar cells.