Invited
How dimensionality and shape anisotropy in perovskite nanocrystals can promote next generation energy materials?

New materials pose new challenges. Lead-halide perovskites have emerged as important optoelectronic materials with excellent efficiencies in photovoltaic and light-emitting applications. These physical properties stand in contrast with recent experimental observations of high dynamic disorder, room temperature structural transformation, and questionable material stability.

I study halide perovskites at the limit of the smallest crystals we can make.

I will show how through synthetic control of cesium lead halide nanocrystal’s shape; we control quantum confinement of excitons with atomic precision (in 2D nanoplates) and achieve anisotropic emission (in 1D nanowires). By control of composition and structural phase transformations we can learn of the thermodynamic nature of this nano-crystal system and improve perovskites infamous stability reputation.

In the case of 2D plates we observe increased excitonic interaction and increased absorption coefficient. In the case of nanowires, we show that the broken symmetry manifests in polarized emission which enables fabrication of highly functional films through 3D printing. In addition, by changing the anion composition facile band gap tunability at room temperature throughout the visible spectrum is achieved.

If time permits, I will discuss exciting opportunities of lead-free perovskites, which we recently learned how to synthesize at the nanoscale.

1. Bekenstein, Y., Koscher, B. A., Eaton, S. W., Yang, P. & Alivisatos, A. P. Highly Luminescent Colloidal Nanoplates of Perovskite Cesium Lead Halide and Their Oriented Assemblies. J. Am. Chem. Soc. 137, 16008–16011 (2015).
2. Bekenstein, Y. et al. The Making and Breaking of Lead-Free Double Perovskite Nanocrystals of Cesium Silver–Bismuth Halide Compositions. Nano Lett. 18, 3502–3508 (2018).
3. Khalfin, S. & Bekenstein, Y. Advances in lead-free double perovskite nanocrystals, engineering band-gaps and enhancing stability through composition tunability. Nanoscale (2019).