van der Waals Epitaxy of Earth-Abundant Zn3P2 on Graphene for Photovoltaics

Earth-abundant semiconducting materials are a potential solution for large-scale deployment of solar cells at a lower cost. Zinc phosphide (Zn3P2) is one such Earth-abundant material with optoelectronic properties suitable for photovoltaics. Herein, we report the van der Waals epitaxy of tetragonal Zn3P2 (α-Zn3P2) on graphene using molecular beam epitaxy. The growth on graphene progresses by the formation of Zn3P2 triangular flakes, which merge to form a thin film with a strong (101) crystallographic texture. Photoluminescence from the Zn3P2 thin films is consistent with previously reported Zn3P2. This work demonstrates that the need for a lattice-matched substrate can be circumvented by the use of graphene as a substrate. Moreover, the synthesis of highquality Zn3P2 flakes and films on graphene brings new material choices for low-cost photovoltaic applications.