CHAPTER 12: Ambipolar Inorganic Two-dimensional Materials for Solar Cells

Ambipolar material refers to a class of materials that can transport both types of charged carriers, electrons and holes. This unique property allows the ambipolar materials to be used as either hole transport layers or electron transport layers or both, and as active p- or n-type absorbers for emerging photovoltaics. The work functions of commonly used metals can be matched with a variety of ambipolar two-dimensional (2D) materials, including graphene and graphene derivatives, MoSe₂, MoTe₂, WSe₂, MoSe₂, ReSe₂, phosphorene, etc., to selectively transport either electrons or holes. The role of such 2D materials in solar cells is of interest since future photovoltaic technologies aspire to be low cost, ultralight, flexible, and capable of being realized by roll-to-roll processing, while allowing for high specific power or watt gram⁻¹ utilization. In this chapter, we provide an insight into the role of different ambipolar 2D materials for silicon, organic, perovskite, and 2D/2D heterojunction solar cells.