Unveiling the dual role of silver-associated defects: the manipulators of luminescence and carrier dynamics in eco-friendly AgIn0.5Ga0.5S2

AgIn0.5Ga0.5S2 has attracted extensive attention in many fields owing to environmental friendliness, low synthetic cost, flexible and adjustable components. Appropriate direct bandgap, no forbidden transition, and high exciton binding energy make it a promising luminescent material. The evolution of the multicomponent system enriches the photoelectric properties and makes its intrinsic defects more complex. Conversely, these defects have an important effect on the photoelectric properties, thus affecting its luminescent performance. However, the microscopic mechanism of point defects corresponding to luminescence observed in experiments is mostly unknown or inferred indirectly for such semiconductors. Here, the mechanism between the microscopic defects and luminescence of AgIn0.5Ga0.5S2 is systematically revealed. Thermodynamic stability shows that AgIn0.5Ga0.5S2 is metastable and has significant competition between the secondary phases. Furthermore, the calculated defect results demonstrate that Ag-associated defects are the behind-the-scenes manipulators. Two shallow-level defects (VAg and Agi) serve as carrier providers, while four deep-level antisite defects (AgIn, AgGa, InAg, and GaAg) act as carrier annihilators. Ultimately, the study of carrier dynamics reveals the adverse effects of four deep-level antisite defects on carriers’ radiative processes. These are intended to provide important guidance for the functional application of AgIn0.5Ga0.5S2 in the field of luminescence.