From defects to devices: Design guidelines for high-performance diamond-based solar cells and single-dopant diodes

This work establishes key technological guidelines for designing diamond-based optoelectronic devices, derived from a first-principles investigation of two architectures: a PIN junction with a boron-vacancy-boron (BVB) intermediate-band absorber, and a PN junction based on phosphorus-vacancy (PV) defects. For the PIN solar cell, practical design principles include: (i ) aligning incident light in the xz -plane to exploit anisotropic absorption; (ii ) using graded junctions to mitigate tunnelling losses at abrupt interfaces; (iii ) targeting an absorber thickness of ∼ 500 nm to balance absorption and carrier extraction; and (iv ) leveraging the high transparency of both contact layers for bifacial device configurations. For the PN diode, the PV-doped diamond operates via impurity-band conduction, making it suitable for degenerate p-type applications such as tunnel diodes or asymmetric junctions, while its temperature-dependent Seebeck anisotropy and sign-reversal offer opportunities for thermal management applications. When paired with phosphorus-doped n-type regions, these defects enable single-dopant junctions that significantly simplify device manufacturing. Using density functional theory with GW corrections, Bethe–Salpeter equation calculations and carrier transport modelling coupled to device electrostatics via a Poisson solver, we show that the BVB defect introduces intermediate bands without degrading diamond’s high carrier mobility or thermal conductivity, while PV-doping provides high conductivity at room temperature through impurity-band transport. Overall, both defect-engineered systems preserve diamond’s superior transport and thermal properties even after doping, offering viable pathways for high-performance diamond optoelectronics. These guidelines provide a practical foundation for fabricating efficient diamond-based photovoltaic and diode devices.