Defect-minimized directly grown graphene-based solar cells

Using plasma-enhanced chemical vapor deposition (PECVD) to directly grow graphene nanowalls (GNWs) on silicon to preparate the solar cells is compatible with current industrial production. However, many defects in the GNWs hinder improvement of the power conversion efficiency (PCE) of solar cells. In this work, we found that the defects in GNWs can be reduced under the condition of keeping the appropriate sheet resistance of GNWs by simultaneously reducing the growth temperature and increasing the growth time. Then, a PCE of 3.83% was achieved by minimizing the defects in the GNWs under the condition of ensuring adequate coverage of GNWs on bare planar silicon. The defects in GNWs were further reduced by adding a poly(3,4-ethylenedioxythiophene) (PEDOT):Nafion passivation coating, and the PCE was significantly improved to 10.55%. Our work provides an innovative path and a simple approach to minimize the defects in graphene grown directly on silicon for high-efficiency solar cells.