Surface Chemistry of Colloidal Cesium Lead Halides Perovskite Nanocrystals and its Impact on the Characteristics of Blue and Green perovskite LEDs
Maryna Bodnarchuk a
a EMPA - Swiss Federal Laboratories for Materials Science and Technology, Überland Strasse, 129, Dübendorf, Switzerland
Invited Speaker, Maryna Bodnarchuk, presentation 115
Publication date: 25th November 2019

Colloidal organic/inorganic lead halide perovskite nanocrystals (NCs) are considered promising blue and green narrow-band emitters for the next-generation light-emitting diodes.  High photoluminescence efficiencies are attained in these materials without epitaxial overcoating of the NC surfaces for electronic passivation of the surface states [1]. The major practical bottleneck of these materials relates to their labile surface chemistry. In particular, typically used ling chain capping ligands are problematic due to their dynamic and loose binding as well as their highly insulating nature. We have recently rationalized the typical observation of a degraded luminescence upon aging or the luminescence recovery upon post-synthesis surface treatments using a simple surface-structure model, supported by DFT calculations [2]. Healing of the surface trap states requires restoration of all damaged PbX6 octahedra and establishing a stable outer ligand shell. Restoration of such a structure, seen as an increase in the luminescence quantum efficiency to 90-100% and improvement in the overall robustness of CsPbBr3 NCs, was attained using a facile post-synthetic treatment with a PbBr2+DDAB (didodecyldimethylammonium bromimde) mixture. In our most recent work [3], we have used DDAB as a sole ligand directly in the synthesis of perovskite NCs. We then used such NCs in LEDs and demonstrate high external quantum efficiencies of up to 3.6% in blue region (460 nm) and 10% in the green region (520 nm).

1.    M. V. Kovalenko, L Protesescu, M. I. Bodnarchuk. Science 2017, 358, 745-750
2.    M. I. Bodnarchuk,S. C. Boehme, S. ten Brinck, C. Bernasconi, Y. Shynkarenko, F. Krieg, R. Widmer, B. Aechlimann, D. Günther, M. V. Kovalenko, I. Infante. ACS Energy Letters 2019, 4, 63–74
3.    Y. Shynkarenko, M. Bodnarchuk et al. ACS Energy Lett, 2019, 4, 11, 2703-2711

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