Energetic, Electronic, and Optical Properties of Intrinsic Charge Carrier-Trapping Defects in KTaO₃: Insights from a Hybrid DFT Study

Potassium tantalate (KTaO₃) has emerged as a leading material for various industrial and technological applications owing to its excellent stability and electronic properties. In spite of extensive research conducted in the past decades, key defects in KTaO₃ are still being investigated. In this study, a detailed systematic calculation using hybrid density functional theory has been carried out to investigate geometry, defect formation energies, and electronic properties of all possible neutral and charged intrinsic vacancy defects in KTaO₃ under various growth conditions. We also extensively examine the role of a vacancy defect cluster in tuning the electronic properties of KTaO₃. Furthermore, we elucidate the role of self-trapped electrons and holes and antisite defects in the optical properties of KTaO₃, and thus a new perspective on the process of different intrinsic point defects in KTaO₃ has been proposed. The formation energy calculation indicates that K-vacancy and its clusters will be readily formed in KTaO₃ in all growth conditions, except under a K-rich environment. We find that O-vacancy, Ta-antisite, and K–O divacancy clusters are deep donors in KTaO₃, while Ta-vacancy, K-antisite, and Ta–O divacancy clusters are deep acceptors. On the other hand, K-vacancy is a shallow acceptor in KTaO₃, and K–O–K trivacancy clusters can act as both acceptors and donors. Based on analysis of formation energies and charge transition level, the present study reveals that O-vacancy, Ta–O, and K–O vacancy clusters mainly contribute to the prominent emission behavior of KTaO₃ in the red–blue–green region. The present study provides critical insights into the microscopic picture of the optical behavior of KTaO₃ perovskites. Thus, this study provides important guidelines for tuning the synthesis conditions to optimize functionalities based on different intrinsic vacancies.