Van der Waals Materials for Atomically-Thin Photovoltaics: Promise and Outlook

Two-dimensional (2D) semiconductors provide a unique opportunity for optoelectronics due to their layered atomic structure and electronic and optical properties. To date, a majority of the application oriented research in this field has been focused on field-effect electronics as well as photodetectors and light emitting diodes. Here we present a perspective on the use of 2D semiconductors for photovoltaic applications. We discuss photonic device designs that enable light trapping in nanometer-thickness absorber layers, and we also outline schemes for efficient carrier transport and collection. We further provide theoretical estimates of efficiency indicating that 2D semiconductors can indeed be competitive with and complementary to conventional photovoltaics, based on favorable energy bandgap, absorption, external radiative efficiency, along with recent experimental demonstrations. Photonic and electronic design of 2D semiconductor photovoltaics represents a new direction for realizing ultrathin, efficient solar cells with applications ranging from conventional power generation to portable and ultralight solar power.