All-inorganic cesium lead halide perovskite nanocrystals (CsPbX3 NCs, X = Cl, Br, I) have attracted much attention recently due to their high photoluminescence quantum yields (50-90%) and narrow emission bands with wide tunability. They combine the advantages of perovskites and quantum dots creating an exceptional material for low-cost optoelectronic and photovoltaic devices. Conducting low-voltage electron energy loss spectroscopy (EELS) on individual NCs, we provide novel insights regarding three important aspects of their microscopic behavior: (i) we explicitly demonstrate the relation between NC size and shape with their bandgap, and that the effective coupling between proximal NCs causes band structure modifications [1]; (ii) the synthesis of CsPbX3 NCs inevitably yields simultaneous formation of other nanostructures, insulating Cs4PbBr6 nanohexagons and hybrid nanospheres [2]; and (iii) drop-casted NCs merge spontaneously at room conditions by seamless stitching of aligned NCs, it can be accelerated by humidity and mild-temperature treatments, while arrested with electron beam irradiation [3]. Further, by using high-resolution induced absorption and emission spectroscopies, we obtain detailed information on carrier dynamics in perovskite NCs [4], their water-resistant encapsulation [5], and on energy exchange within their ensembles [6]. Finally, we will also report on the on-going quest of carrier multiplication in these materials.

[1] J. Lin et al. Nano Lett. 2016, 16, 7198.
[2] C. de Weerd et al. C 2017, 121, 19490.
[3] L. Gomez et al. Adv. Energy Mater. 2017, under consideration.
[4] E. M. L. D. de Jong et al. J. Phys. Chem. C 2017, 121, 1941.
[5] L. Gomez et al. Nanoscale 2017, 9, 631.
[6] C. de Weerd et al. J. Phys. Chem. C 2016, 120, 13310.