Impact of defects on the opto-electronic properties of monolayer GeSe; a many-body perturbation theory perspective

An accurate and detailed knowledge of the influence of defects will be central to the design of promising new 2D materials. Due to their reduced dimensionality and screening, these materials are even more likely to be impacted by defects than their 3D counterparts. We employ first-principles many-body perturbation theory within the GW/BSE approximation to investigate the influence of point defects on the opto-electronic properties of a monolayer semiconductor composed of GeSe. We systematically study a series of charged vacancies, their trap state energies, and their impact on optical absorption. We determine that the excitonic properties of the material are significantly affected by the presence of defects, with implications for devices fabricated using this material system.