Research Seminar of Prof. Andrey L. Rogach fromCity University of

Hong Kong

Lecture Time: 10:00 on 31st Aug, 2016

Lecture Room: C501 of National Science Park

Lecture Title:Perovskite nanocrystals: synthesis, hybrid structures and their use in light emitting devices

Andrey L. Rogach

Department of Physics and Materials Science & Centre for Functional Photonics, City University of

Hong Kong, Hong Kong S.A.R.

Abstract

Starting in 2009, perovskite materials in the form of bulk thin films have attracted a lot of attention in the area of solar energy generation. Nanoscale colloidal perovskite nanocrystals are a relatively new subject of research. We demonstrate the size-tunability of the bandgap of narrow size dispersion CH3NH3PbBr3 perovskite quantum dots by using temperature to exert control over the ligand-assisted re-precipitation process [1]. The emission was in the 475-520 nm range, with an outstandingly high quantum yield of 74% to 93%. We further present an approach towards stable solid-state perovskite based luminophores with different emission colors via surface protection of CsPbX3 (X = Br or I) with a polyhedral oligomeric silsesquioxane (POSS) [2]. This treatment results in water resistant perovskite nanocrystal powders, and prevents otherwise easy anion exchange between perovskite nanocrystals of different composition mixed together in the solid state, which allows us to preserve their distinct emission spectra. We subsequently used mixtures of green emitting POSS-CsPbBr3 and red-emitting POSS-CsPb(Br/I)3 nanocrystal powders to fabricate single layer all-perovskite down conversion white light emitting devices (LEDs). High emission quantum yield, easily tuned emission colors, and high color purity of perovskite quantum dots make this class of material attractive for light source or display applications, which has been recently realized for electroluminescent LEDs through the interface engineering with perfluorinated ionomer [3].
1. H. Huang, A. S. Susha, S. V. Kershaw, T. F. Hung, A. L. Rogach. Control of Emission Color of High Quantum Yield CH3NH3PbBr3 Perovskite Quantum Dots by Precipitation Temperature. Adv. Sci. 2015, 2, 1500194.
2. H. Huang, B. Chen, Z. Wang, T. F. Hung, A. S. Susha, H. Zhong, A. L. Rogach. Water Resistant CsPbX3 Nanocrysals Coated by Polyhedral Oligomeric Silsesquioxane and their Use as Solid State Luminophores in All-Perovskite White Light Emitting Devices. Chem. Sci., in press.
3. X. Zhang, H. Lin, H. Huang, C. Reckmeier, Y. Zhang, W. C. H. Choy, A. L. Rogach. Enhancing the Brightness of Cesium Lead Halide Perovskite Nanocrystal Based Green Light-Emitting Devices through the Interface Engineering with Perfluorinated Ionomer. NanoLett. 2016, 16, 1415.

Biography

Andrey L. Rogach is a Chair Professor of Photonics Materials at the Department of Physics and Materials Science, and the Founding Director of the Centre for Functional Photonics at City University of Hong Kong. He received his Ph.D. in chemistry (1995) from the Belarusian State University in Minsk, and worked as a staff scientist at the University of Hamburg (Germany) from 1995 to 2002. From 2002-2009 he was a lead staff scientist at the Ludwig-Maximilians-Universität in Munich (Germany), where he completed his habilitation in experimental physics. His research focuses on synthesis, assembly and optical spectroscopy of colloidal semiconductor and metal nanocrystals and their hybrid structures, and their use for energy transfer, light harvesting and light emission. He has published over 270 papers and book contributions in these areas, which have been cited more than 21,000 times so far (h-index 78). His name is on the list of Top 100 Materials Scientists and on the list of Top 20 Authors publishing on nanocrystals in the past decade by Thomson Reuters, ISI Essential Science Indicators. Andrey Rogach is an Associate Editor of ACS Nano, and holds honorary appointments at Trinity College Dublin (Ireland), Xi'An Jiaotong University, Jilin University and Peking University (China).