Colour emission tunability in flexible carbon dot based ionogels and light emitting devices
Speaker:Prof. Andrey Rogach
Chair Professor
Department of Physics and Materials Science
Centre for Functional Photonics (CFP)
City University of Hong Kong
Date & Time:24 Apr 2014 (Thursday) 11:00 - 12:00
Organized by:Department of Electromechanical Engineering


Multicolour luminescent materials are of immense importance nowadays, while it constitutes a challenge to achieve both luminescence colour tunability, transparency, and flexibility at the same time. Carbon dots (CD) have emerged over the recent few years as a new class of light emitting materials exhibiting bright, excitation wavelength dependent emission We show how sub-nanometer CDs fluorescing strongly across the visible spectrum can be surface functionalized and incorporated into highly flexible hybrid materials by combination with ionic liquids within silica gel networks to form CD-ionogels with properties promising for fabrication of flexible displays and other optical technologies [1]. We demonstrate how the emission from such hybrid materials can be tuned across a large range of the CIE display gamut giving full-colour performance. Furthermore, we introduce CD-based light-emitting devices (LEDs) with driving current controlled color change. [2] These devices consist of a CD emissive layer sandwiched between an organic hole transport layer and an organic or inorganic electron transport layer fabricated by solution processing. By tuning the device structrure and the injecting current density (by changing the applied voltage), multi-color emission of blue, cyan, magenta, and white can be obtained from the same CDs.

  1. Y. Wang, S. Kalytchuk, Y. Zhang, H. C. Shi, S. V. Kershaw, A. L. Rogach. J. Phys. Chem. Lett. 2014, 5, 1412.
  2. X. Zhang, Y. Zhang, Y. Wang, S. Kalytchuk, S. V. Kershaw, Y. Wang, P. Wang, T. Zhang, Y. Zhao, H. Zhang, T. Cui, Y. Wang, J. Zhao, W. W. Yu, A. L. Rogach. ACS Nano, 2013, 7, 11234.

Andrey L. Rogach is a Chair Professor of Photonics Materials at the Department of Physics and Materials Science, City University of Hong Kong, and a Director of the Centre for Functional Photonics at CityU. 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. Since 2008 he is also an Adjunct Professor at Trinity College Dublin (Ireland). 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 biosensing. He has published over 250 papers and book contributions in these areas, which have been cited more than 16,000 times so far (h-index 67). 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.