Ing. Matúš Kaintz

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.

Dopant-dopant and dopant-vacancy complexes in diamond can be exploited for the development of quantum computers, single-photon emitters, high-precision magnetic field sensing, and nanophotonic devices. While some dopant-vacancy complexes such as nitrogen- and silicon-vacancy centers are well studied, studies of other dopant and/or vacancy clusters are focused mainly on defect detection, with minimal investigation into their electronic features or how to tune their electronic and optical properties for specific applications. To this aim, we perform a thorough analysis of the coupled structural and electronic features of different dopant-dopant and dopant-vacancy cluster defects in diamond by means of first-principles calculations. We find that doping with 𝑝-type (𝑛-type) dopant does not always lead to the creation of 𝑝-type (𝑛-type) diamond structures, depending on the kind of cluster defect. We also identify the quantum mechanical descriptors that are most suitable to tune the electronic band gap about the Fermi level for each defect type. Finally, we propose how to choose suitable dopant atomic types, concentrations, and geometric environments to fabricate diamond-based materials for several technological applications such as electrodes, transparent conductive materials, intermediate-band photovoltaics, and multicolor emitters, among others.

Diamond-based compounds are ideal materials to build nanoengineered devices with wide applicability in nanophotonics, optomechanics, photovoltaics and electronics, where tuning the width and the character of the electronic band gap is paramount. While the available information is focused on specific aspects of the material preparation and response, a general understanding of how the entangled geometric and electronic properties determine the characteristics of the band gap is missing. The present work aims to tackle this challenge by means of first principle simulations. We show that specific charge distributions in the ion environment determine the width of the band gap; in order to control it, we suggest how to select suitable dopant atomic types and how to impose specific structural deformations. We also propose different routes to switch the character of the band gap from indirect to direct. The results pave new avenues aimed to design diamond-based nanostructured materials with targeted optical and electronic properties. The outcomes of the present work are general and can therefore be promptly applied to the study of optical and electronic materials irrespective of their chemical composition and atomic topology.