PEROVSKITE CsPbBr3 NANOCRYSTALS WITH OLEIC LIGANDS GRAFTED ON ZnO SURFACES: DFT STUDY OF ELECTRONIC PROPERTIES

Semiconductor CsPbBr3 (CPB) perovskite materials exhibit narrow band gap (about 2.5 eV) and possess very fast (hundreds of picoseconds) and strong free exciton luminescence (green at the nanoscale).CPB combination with ZnO microrods can further enhance photoluminescence.In this work the impact of ZnO polar and non-polar surface terminations on the properties of ZnO system with CPB nanocrystals passivated by oleic ligands is investigated.Calculations of structure and electronic properties by density functional theory (DFT) methods are compared on polar surfaces (Zn-face (0001), O-face (0001 )), and non-polar surfaces ((101 0) and (112 0)) before and after grafting CPB crystal with oleic ligands (OA, OAm).We find that on Znface ZnO surface the attachment of CPB with ligands causes increase of the band gap whereas on the other three ZnO surfaces the attachment of CPB with ligands caused the decrease of the band gap.The position of Fermi level with respect to HOMO and LUMO is also changing, indicating possible charge transfer and doping effects.