Flexible graphene/silicon heterojunction solar cells

Graphene/silicon heterojunction solar cells have attracted intensive research interest owing to their simple device structure as well as their low-cost process capability at room temperature. However, the use of thick silicon substrates hampers their application in flexible solar cells, despite the high flexibility of graphene. Here, we report the construction of flexible graphene/silicon solar cells by taking advantage of the high flexibility of ultrathin Si substrates. By systemically optimizing the device structures, including performing surface passivation on Si, inserting a layer of poly(3-hexylthiophene) (P3HT) as an electron blocking layer, and controlling the layer number and doping of graphene, a power conversion efficiency of 8.42% was successfully achieved. The photovoltaic characteristics of the graphene/ultrathin silicon heterojunctions were further evaluated under bending conditions, revealing their excellent flexibility and durability. Our work paves the way for low-cost, high-performance, flexible graphene/silicon heterojunction solar cells.