Nanocomposites and nanomaterials

Blue and yellow light electroluminescence in a multilayer WOLED using Ir complexes.
Ivaniuk K.B.1, Kutsiy S.A. 1, Helzhynskyy I.I.1, Tan X.2, Stakhira P.Y.1, Grazulevicius J.V. 2
1 Lviv Polytechnic National University, Bandera str., 12, Lviv 79013, Ukraine.
2 Kaunas University of Technology, K. Baršausko g. 59, 51423 Kaunas, Lithuania

WHITE organic light-emitting diode (WOLED) was studied by a lot of scientists because of interests in terms of eco-friendly lighting sources, since no mercury has been involved and in terms of OLED display for a large-sized and flexible substrate [1,2]. Typically, two methods were excited to realize white color, one is 4-subpixel color filter of RGBW, [2] and the other is tandem structure in which a charge generation layer connects two independent OLED units. Some groups reported white luminance efficiency, using 3-independent stack WOLED in which each OLED unit emitted one of three main RGB color [3]. Although multi-stack structure has been better with higher luminance efficiency, there are demerits that the voltage is increased and the technologicaly part was very complicated. 
Thus, to our mind, one WOLED with double emittion is an optimal structure, considering luminance efficiency and facility investment. The strategy of forming the WOLED structure was to combine a high-efficiency exciplex that emits long-wave light and an organometallic complex of blue phosphorescent emission. On the prepared substrates, the WOLED structure ITO / CuI / mMTDATA / Ir (ppz) 3 / m-MTDATA / P6 / Ir (ppz) 3 / mCP: FIrpic / TPBi / Ca: Al was formed by thermal vacuum deposition. The CIE (x, y) color coordinates for the developed WOLED structure are (0.38, 0.4), which are in the white color range. Іn addition, at increased current densities up to 160 mA/cm2, the electroluminescence spectrum does not change, indicating good WOLED stability.

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2.	Hong Seok Choi., et al. // Journal of Display Tech..- 2009.-5.-546-551.
3.	Ramon Springer, et al. // Optics Express- 2016.-24.- 28131-28142