Organic Light-Emitting Devices

Organic Light-Emitting Devices (OLEDs) can be fabricated with low-cost and low-temperature methods on a wide variety of substrates, such as flexible and ultra-thin substrates, via solution-based processes, such as spin-coating, ink-jet printing, doctor blade and spray coating.

Adapted from: https://doi.org/10.1038/s41566-021-00855-2

Our contribution to the OLED development has focused mainly on 2 approaches:

a) Photochemical patterning and colour tuning in single-layer OLEDs

We investigated the changes in emission colour of thin films based on fluorescent dyes and phosphorescent (organometallic) compounds, blended with a conjugated polymer host, upon photochemical protonation of their basic sites. This enabled patterning of the three basic colours (RGB) in a single polymer layer, facilitating fabrication of multi-colour and white light OLEDs.

b) Interface engineering of organic/hybrid light-emitting devices

Thin films of inorganic materials, such as metal oxides (WOx, MoOx, HyMoOx) and polyoxometalates (H3PW12O40), and organic materials, such as porphyrins and triphenylsulfonium salts, were employed as electron/hole injecting layers in organic/hybrid OLEDs . Control over stoichiometry of the metal oxides and over film forming properties via solution deposition methods of the other materials – some of them employed for the first time as interfacial layers – resulted in dramatic increase in device efficiencies and overall performance.

  • 1)      Advances in solution-processed near-infrared light-emitting diodes. Vasilopoulou, M., Fakharuddin, A., García de Arquer, F. P., Georgiadou, D. G., Kim, H., Mohd Yusoff, A. R. b., Gao, F., Nazeeruddin, M. K., Bolink, H. J. & Sargent, E. H. Nature Photonics 15, 656-669, doi: https://doi.org/10.1038/s41566-021-00855-2(2021).

    2)      Flexible nanogap polymer light-emitting diodes fabricated via adhesion lithography (a-Lith). Wyatt-Moon, G., Georgiadou, D. G., Zoladek-Lemanczyk, A., Castro, F. A. & Anthopoulos, T. D. Journal of Physics: Materials 1, 01LT01, doi:https://doi.org/10.1088/2515-7639/aadd57 (2018).

    3)      Vasilopoulou, M., Georgiadou, D. G., Davazoglou, D., Savaidis, S. P. & Stathopoulos, N. A. in Physica Status Solidi C: Current Topics in Solid State Physics Vol. 14 Physica Status Solidi C-Current Topics in Solid State Physics (ed S. Hildebrandt)  (2017).

    4)      Efficient electron injecting layer for PLEDs based on (PLAGH)(2)[ZnCl4]. Jelic, M. G., Georgiadou, D. G., Radanovic, M. M., Romcevic, N. Z., Giannakopoulos, K. P., Leovac, V. M., Nad, L. F. & Vojinovic-Jesic, L. S. Optical and Quantum Electronics 48, doi: https://doi.org/10.1007/s11082-016-0547-5 (2016).

    5)      Solution processed multi-color organic light emitting diodes for application in telecommunications. Vasilopoulou, M., Georgiadou, D. G., Soultati, A., Douvas, A. M., Papadimitropoulos, G., Davazoglou, D., Pistolis, G., Stathopoulos, N. A., Kamalakis, T., Alexandropoulos, D., Vainos, N., Politi, C. T., Palilis, L. C., Couris, S., Coutsolelos, A. G. & Argitis, P. Microelectronic Engineering 145, 21-28, doi: https://doi.org/10.1016/j.mee.2015.02.005 (2015).

    6)      Reflection and transmission calculations in a multilayer structure with coherent, incoherent, and partially coherent interference, using the transmission line method. Stathopoulos, N. A., Savaidis, S. P., Botsialas, A., Ioannidis, Z. C., Georgiadou, D. G., Vasilopoulou, M. & Pagiatakis, G. Applied Optics 54, 1492-1504, doi: https://doi.org/10.1364/ao.54.001492 (2015).

    7)      Theoretical study on the electronic structure of triphenyl sulfonium salts: Electronic excitation and electron transfer processes. Petsalakis, I. D., Theodorakopoulos, G., Lathiotakis, N. N., Georgiadou, D. G., Vasilopoulou, M. & Argitis, P. Chemical Physics Letters 601, 63-68, doi: https://doi.org/10.1016/j.cplett.2014.03.086 (2014).

    8)      All-Organic Sulfonium Salts Acting as Efficient Solution Processed Electron Injection Layer for PLEDs. Georgiadou, D. G., Vasilopoulou, M., Palilis, L. C., Petsalakis, I. D., Theodorakopoulos, G., Constantoudis, V., Kennou, S., Karantonis, A., Dimotikali, D. & Argitis, P. ACS Applied Materials & Interfaces 5, 12346-12354, doi: https://doi.org/10.1021/am402991b (2013).

    9)      Influence of the anion on the optoelectronic characteristics of triphenylsulfonium salts modified polymer light emitting devices. Georgiadou, D. G., Palilis, L. C., Vasilopoulou, M., Pistolis, G., Dimotikali, D. & Argitis, P. Synthetic Metals 181, 37-44, doi: https://doi.org/10.1016/j.synthmet.2013.08.002 (2013).

    10)  High performance organic light emitting diodes using substoichiometric tungsten oxide as efficient hole injection layer. Vasilopoulou, M., Papadimitropoulos, G., Palilis, L. C., Georgiadou, D. G., Argitis, P., Kennou, S., Kostis, I., Vourdas, N., Stathopoulos, N. A. & Davazoglou, D. Organic Electronics 13, 796-806, doi: https://doi.org/10.1016/j.orgel.2012.01.008 (2012).

    11)  Barrierless hole injection through sub-bandgap occupied states in organic light emitting diodes using substoichiometric MoO(x) anode interfacial layer. Vasilopoulou, M., Palilis, L. C., Georgiadou, D. G., Kennou, S., Kostis, I., Davazoglou, D. & Argitis, P. Applied Physics Letters 100, doi: https://doi.org/10.1063/1.3673283 (2012).

    12)  Reduced transition metal oxides as electron injection layers in hybrid-PLEDs. Vasilopoulou, M., Georgiadou, D. G., Palilis, L. C., Argitis, P., Kennou, S., Sygellou, L., Konofaos, N., Iliadis, A., Kostis, I., Papadimitropoulos, G. & Davazoglou, D. Microelectronic Engineering 90, 59-61, doi: https://doi.org/10.1016/j.mee.2011.05.017 (2012).

    13)  Effect of triphenylsulfonium triflate addition in wide band-gap polymer light-emitting diodes: improved charge injection, transport and electroplex-induced emission tuning. Georgiadou, D. G., Palilis, L. C., Vasilopoulou, M., Pistolis, G., Dimotikali, D. & Argitis, P. RSC Advances 2, 11786-11792, doi: https://doi.org/10.1039/c2ra21709k (2012).

    14)  Reduction of tungsten oxide: A path towards dual functionality utilization for efficient anode and cathode interfacial layers in organic light-emitting diodes. Vasilopoulou, M., Palilis, L. C., Georgiadou, D. G., Douvas, A. M., Argitis, P., Kennou, S., Sygellou, L., Papadimitropoulos, G., Kostis, I., Stathopoulos, N. A. & Davazoglou, D. Advanced Functional Materials 21, 1489-1497, doi: https://doi.org/10.1002/adfm.201002171 (2011).

    15)  Reduced molybdenum oxide as an efficient electron injection layer in polymer light-emitting diodes. Vasilopoulou, M., Palilis, L. C., Georgiadou, D. G., Argitis, P., Kennou, S., Sygellou, L., Kostis, I., Papadimitropoulos, G., Konofaos, N., Iliadis, A. A. & Davazoglou, D. Applied Physics Letters 98, doi: https://doi.org/10.1063/1.3557502 (2011).

    16)  Incorporating triphenyl sulfonium salts in polyfluorene PLEDs: an all-organic approach to improved charge injection. Georgiadou, D. G., Palilis, L. C., Vasilopoulou, M., Pistolis, G., Dimotikali, D. & Argitis, P. Journal of Materials Chemistry 21, 9296-9301, doi: https://doi.org/10.1039/c0jm04567e (2011).

    17)  Theoretical investigation on the effect of protonation on the absorption and emission spectra of two amine-group-bearing, red push'pull emitters, 4-dimethylamino-4′-nitrostilbene and 4-(dicyanomethylene)-2-methyl-6- p -(dimethylamino) styryl-4H-pyran, by DFT and TDDFT Calculations. Petsalakis, I. D., Georgiadou, D. G., Vasilopoulou, M., Pistolis, G., Dimotikali, D., Argitis, P. & Theodorakopoulos, G. Journal of Physical Chemistry A 114, 5580-5587, doi: https://doi.org/10.1021/jp100338d (2010).

    18)  A water soluble inorganic molecular oxide as a novel efficient electron injection layer for hybrid light-emitting diodes (HyLEDs). Palilis, L. C., Vasilopoulou, M., Georgiadou, D. G. & Argitis, P. Organic Electronics 11, 887-894, doi: https://doi.org/10.1016/j.orgel.2010.02.004 (2010).

    19)  Photopatterned PLED arrays for biosensing applications. Vasilopoulou, M., Georgiadou, D. G., Palilis, L. C., Botsialas, A., Petrou, P. S., Kakabakos, S. E. & Argitis, P. Microelectronic Engineering 86, 1511-1514, doi: https://doi.org/10.1016/j.mee.2009.01.063 (2009).

    20)  Flexible organic light emitting diodes (OLEDs) based on a blue emitting polyfluorene. Vasilopoulou, M., Palilis, L. C., Botsialas, A., Georgiadou, D. G., Bayiati, P., Vourdas, N., Petrou, P. S., Pistolis, G., Stathopoulos, N. A. & Argitis, P. Physica Status Solidi (C) Current Topics in Solid State Physics 5, 3658-3662, doi: https://doi.org/10.1002/pssc.200780214 (2008).

    21)  A combined experimental and simulation study on thickness dependence of the emission characteristics in multicolor single layer organic light-emitting diodes. Stathopoulos, N. A., Vasilopoulou, M., Palilis, L. C., Georgiadou, D. G. & Argitis, P. Applied Physics Letters 93, 83310, doi: https://doi.org/10.1063/1.2977479 (2008).

    22)  Energy transfer processes among emitters dispersed in a single polymer layer for colour tuning in OLEDs. Georgiadou, D. G., Vasilopoulou, M., Pistolis, G., Palilis, L., Dimotikali, D. & Argitis, P. Physica Status Solidi (A) Applications and Materials 205, 2526-2531, doi: https://doi.org/10.1002/pssa.200780204 (2008).

    23)  Tuning the emitting color of organic light-emitting diodes through photochemically induced transformations: Towards single-layer, patterned, full-color displays and white-lighting applications. Vasilopoulou, M., Georgiadou, D., Pistolis, G. & Argitis, P. Advanced Functional Materials 17, 3477-3485, doi: https://doi.org/10.1002/adfm.200700231 (2007).

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