Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
Publication date: 4th October 2020
Traditional ligand engineering approaches employed in colloidal nanocrystals (NCs), appear to have a limited functionality in lead halide perovskite NCs, resulting in highly dynamic ligand binding to the NC surface and partial loss of colloidal and structural stability. Among the various surface chemistry approaches employed to circumvent such liability, treatment by didodecyldimethylammonium bromide (DDAB) appears highly beneficial for CsPbBr3 NCs, as it dramatically improves the material chemical durability while efficiently healing surface traps and increasing the NC emission quantum yield[1].
Herein, we present a photophysical study that demonstrates in detail the impact of the DDAB treatment on the energetics and dynamics of photoluminescence (PL) in CsPbBr3 NC films. Temperature-dependent PL experiments analysed by a modified Arrhenius model, provide evidence of exciton trapping at shallow NC traps of the order of 40 meV, while deep traps appear efficiently passivated. As temperature increases, efficient exciton de-trapping from the shallow traps occurs, repopulating the NC core states and resulting in room temperature emission QYs in the excess of 80%. Temperature-dependent transient PL measurements further confirm the findings of the steady-state PL study, providing a quantitative estimation of the radiative lifetime and emission yield across the 10 to 300 K range. The work provides qualitative and quantitative support for the superb surface passivating properties of DDAB ligands on CsPbBr3 perovskite nanocrystals.
Acknowledgements: We acknowledge financial support from the Research Promotion Foundation of Cyprus, under the "NEW STRATEGIC INFRASTRUCTURE UNITS- YOUNG SCIENTISTS" Programme (Grant Agreement No. "INFRASTRUCTURES/1216/0004", Grant "NANOSONICS")
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