Earth-abundant semiconductors are attracting increasing attention as candidates for sustainable and scalable photovoltaic technologies. Among them, zinc phosphide (Zn₃P₂) remains relatively underexplored despite its highly favorable optoelectronic properties, including a direct band gap of ~1.5 eV, a high absorption coefficient in the visible (>10⁴ cm⁻¹), carrier diffusion length in the range of 5−10 μm and intrinsic p-type.[1] In addition, its tolerance to stoichiometric variations enables a wide tunability of carrier concentration, making it a versatile platform for device design. However, the development of efficient Zn₃P₂-based solar cells has historically been hindered by limitations in both material quality and device architecture. For decades, device performance remained largely stagnant, with Schottky and heterojunction solar cells constrained by resistive losses, interface recombination, and incomplete carrier collection, even when improvements in crystallinity were achieved. [2]

Here, we present a device-focused approach to Zn₃P₂ photovoltaics, enabled by recent advances in thin-film growth at mild temperatures. Using molecular beam epitaxy (MBE) and selective area epitaxy (SAE), we achieve improved control over morphology, defect formation, and interfaces.[1,3] In particular, SAE enables nanoscale strain relaxation, leading to high-quality coalesced thin films with enhanced transport properties, including hole mobilities exceeding 500 cm²/V·s.[3,4] Building on this materials platform, we demonstrate the progression of Zn₃P₂-based photovoltaic devices from early heterojunction designs toward more optimized architectures.[4] Through combined electrical, optical, and nanoscale characterization, we identify the dominant loss mechanisms, including recombination at the front interface and limited carrier extraction. Leveraging these insights, we have recently achieved record device performance for Zn₃P₂-based solar cells, highlighting the impact of improved material quality coupled with refined device design.

Finally, we discuss ongoing strategies toward next-generation architectures based on selective contacts, aimed at enhancing carrier selectivity and suppressing interfacial recombination.[5] These approaches provide a clear pathway to further improve efficiency and establish Zn₃P₂ as a competitive, earth-abundant absorber for future photovoltaic technologies.