Publication date: 2nd November 2020
Insights into the interparticle mixing of CsPbBr3 and CsPbI3 nanocubes: halide ion migration and kinetics
Anamul Haque, Trupthi Devaiah C, Pralay K. Santra*
Centre for Nano and Soft Matter Sciences, Jalahalli, Bengaluru, India-560013
Email ID: anamul@cens.res.in, psantra@cens.res.in*
The all-inorganic halide perovskite nanocrystals (NCs) forms a highly dynamic crystal lattice due to its ionic bonding properties, which easily leads to fast ion exchange at solid−gas, solid−liquid, and liquid−liquid interface. Therefore, the mixing of pre-synthesized CsPbBr3 and CsPbI3 NCs at room temperature leads to the formation of heterostructured mixed halide CsPbBr3−xIx NCs1,2 which prevents to make a white light emitting diode (w-LED) using the red-green combination CsPbX3 NCs on blue LED.
Understanding the reaction mechanism particularly the effect of the relative concentration of the nanocrystals and the kinetics of interparticle mixing is essential for fundamental aspects and device applications.
Here, we probed the kinetics of ion migration through time-dependent steady-state photoluminescence (PL) spectroscopy. We found three primary PL peaks after the mixing of NCs – bromide side peak, iodide side peak, and a new peak that emerges during the reaction. The reaction follows first-order kinetics with activation energy of 0.75 ± 0.05 eV. We propose that the free oleylammonium halides which are in dynamic equilibrium with the NCs, eventually promote interparticle mixing that follows the anion migration from the surface to the core of the nanocrystal, which is the rate-limiting step. Overall, the inherent reaction rate between the halide anions and the nanocrystals governs the reaction kinetics.3
Reference:
1. V. K. Ravi, P. K. Santra, N. Joshi, J. Chugh, S. K. Singh, H. Rensmo, P. Ghosh, A. Nag, J. Phys. Chem. Lett. 2017, 8, 4988-4994.
2. A. Haque, V. K. Ravi, G. S. Shanker, I. Sarkar, A. Nag, P. K. Santra, J. Phys. Chem. C, 2018, 122, 13399-13406.
3. A. Haque, T. Devaiah C, A. B. Dey, P. K. Santra, Nanoscale, 2020, 12, 20840-20848.
Department of Science and Technology, Govt. of India, TPF Nanomission, Centre for Nano and Soft Matter Sciences.
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