Zn3P2 thin films grown on graphene for earth abundant solar cells and recyclable substrates

Silicon-based photovoltaics (PV) dominate the market but face limitations due to high production costs and energy-intensive processing. Zinc phosphide (Zn₃P₂) offers a more sustainable alternative, as it is composed of earth-abundant elements and exhibits a direct bandgap (~1.5 eV), high visible light absorption, and long minority carrier diffusion length, making it suitable for thin-film solar cells. However, device efficiencies have remained low (~6%) due to defects arising from lattice mismatch with conventional substrates like GaAs and InP.

To overcome these challenges, quasi-van der Waals epitaxy (Q-VdWe) on 2D materials like graphene presents a promising solution. This technique eliminates the need for lattice matching, reducing strain and defects, and allows high-quality Zn₃P₂ growth on abundant and reusable graphene. Furthermore, Zn₃P₂ films grown on graphene-coated SiC substrates can be peeled off, enabling substrate recyclability, significantly lowering production costs, and enhancing sustainability.

Our research focuses on investigating grain boundaries and defects in Zn₃P₂ films grown via Q-VdWe. Early results reveal strain and localized emissions at grain boundaries, possibly due to strain or vacancies. Further analysis will determine the origin and impact of these defects on performance, with the goal of optimizing Zn₃P₂ as a sustainable and efficient PV material.