Towards controlled synthesis and better understanding of blue shift of the CaS crystals
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For the first time, the calcium sulfide (CaS) photoluminescent (PL) emission blue shift synthesized by the microwave-assisted solvothermal (MAS) method was examined to understand its key role in the PL activity. PL emission in the visible region showed a blue shift with synthesis time variations. In addition, we also investigated the electronic structure using first-principles calculations based on density functional theory (DFT) which was applied to periodic models at the B3LYP level. Two models were selected to simulate the effects of structural deformation on the electronic structure: (1) the ordered model (o-CaS) and (2) the disordered model (d-CaS). This PL emission shift is linked to distortions and defects which generate modifications in the electronic states and facilitate the possibility of numerous decay transactions to the valence band (VB).