Single-photon emitters (SPEs) in hexagonal boron nitride (hBN) have emerged as promising candidates for scalable, room-temperature quantum photonics due to their bright emission, chemical robustness, and ease of integration into on-chip architectures. Despite this potential, the microscopic origin of many hBN emitters remains uncertain, and the influence of postprocessing treatments on their optical performance is not yet fully understood. This thesis addresses these challenges by systematically studying the photophysical properties of hBN point defects and evaluating how selected post-processing treatments (PPTs) modify their emission behavior.

Specifically, the focus in this work are point defects in hBN nanoflakes and the effect of ozone treatment and high-temperature annealing in different atmospheres on the measured characteristics. The characterization is performed in terms of their single-photon capabilities, photon flux, and stability. These characteristics are compared in the treated samples with those observed in the untreated samples. A statistical analysis of the characteristics measured on 577 untreated emitters and 383 emitters from post-processed samples is presented. The results show that, although no improvement in stability is achieved, the single-photon purity improves significantly with the applied treatments, therefore leading to a greater availability of stable single-photon emitters compared to the untreated samples.

To contextualize the experimental results, the extracted emitter properties – such as zerophonon line positions, lifetimes, and Debye–Waller factors – are compared with density func- tional theory (DFT) predictions available in the hBN defect database, enabling the identification of several plausible defect structures, with a focus on carbon-based configurations. In addition, a relative calibration of two single-photon avalanche diode (SPAD) detectors using a selected hBN single-photon emitter is presented. Together, these findings provide new insight into the optical behavior of hBN point defects, the role of post-processing in modifying their quantum emission, and the suitability of hBN emitters as reference sources in detector characterization