Proceedings of September Meeting 2016 (NFM16)
Publication date: 14th June 2016
Perovskite materials such as lead halides (PbX3) have become a popular research topic in the recent years as their optoelectronic properties make these materials great candidates for various photovoltaic applications. Their relatively easy synthesis and potential to be used in various commercial applications have attracted the attention of many researchers, and an increasing amount of work is done to increase the understanding of these materials. A reliable synthesis method was not published until the beginning of 2015 and, as of yet, the knowledge about perovskite nanocrystals is still limited. [1] Especially the support of computational tools still needs to be developed, as models of these materials were not available.
In this work, we present realistic cubic perovskite nanocrystal models that have been assembled based on experimental results. We show with the density of states of CsPbBr3 nanocrystals, calculated using density functional theory, that any excessive bromide ions on the surface can serve as localized trap states, leading to a loss of photoluminescence quantum yield. Moreover, we show that the experimentally determined Cs:Pb ratio does not match the Cs:Pb ratio of an ideal cubic perovskite model. [2] Our models have a Cs:Pb ratio that matches experimental results while also achieving a clean band gap, demonstrating that they represent realistic perovskite nanocrystals well. These models allow for a better understanding of the surface chemistry and give more insight on the properties of perovskite nanocrystals.
[1] L. Protesescu, S. Yakunin, M. I. Bodnarchuk M, F. Krieg, R. Caputo, C. H. Hendon, R. X. Yang, A. Walsh, M. V. Kovalenko, Nanocrystals of Cesium Lead Halide Perovskites (CsPbX(3), X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut. Nano Lett. 2015, 15 (6), 3692-3696
[2] J. De Roo, M. Ibáñez, P. Geiregat, G. Nedelcu, W. Walravens, J. Maes, J. C. Martins, I. Van Driessche, M. V. Kovalenko, Z. Hens, Highly Dynamic Ligand Binding and Light Absorption Coefficient of Cesium Lead Bromide Perovskite Nanocrystals. ACS Nano. 2016, 10 (2), 2071-2081
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