Institute of Materials Science and Nanotechnology (UNAM)

Permanent URI for this communityhttps://hdl.handle.net/11693/115649

Browse

Browsing Institute of Materials Science and Nanotechnology (UNAM) by Author "Abiyasa, A. P."

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    On the triplet distribution and its effect on an improved phosphorescent organic light-emitting diode
    (AIP Publishing, 2012-08-28) Liu, S. W.; Divayana, Y.; Abiyasa, A. P.; Tan S.T.; Demir, Hilmi Volkan; Sun, X. W.
    We reported phosphorescent organic light-emitting diodes with internal quantum efficiency near 100% with significantly reduced efficiency roll-off. It was found that the use of different hole transporting layer (HTL) affects the exciton distribution in the emission region significantly. Our best device reaches external quantum efficiency (EQE), current, and power efficiency of 22.8% +/- 0.1%, 78.6 +/- 0.2 cd/A, 85 +/- 2 lm/W, respectively, with half current of 158.2 mA/cm(2). This considerably outperforms the control device with N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB) (HTL) and 4,4'-N,N'-dicarbazole-biphenyl (host) with maximum EQE, current and power efficiency of 19.1% +/- 0.1%, 65.6 +/- 0.3 cd/A, 67 +/- 2 lm/W, respectively, with half current of only 8.1 mA/cm(2).
  • Thumbnail Image
    ItemOpen Access
    Quantum dot light-emitting diode with quantum dots inside the hole transporting layers
    (American Chemical Society, 2013) Leck K.S.; Divayana, Y.; Zhao, D.; Young, X.; Abiyasa, A. P.; Mutlugun, E.; Gao, Y.; Liu, S.; Tan S.T.; Sun, X. W.; Demir, Hilmi Volkan
    We report a hybrid, quantum dot (QD)-based, organic light-emitting diode architecture using a noninverted structure with the QDs sandwiched between hole transporting layers (HTLs) outperforming the reference device structure implemented in conventional noninverted architecture by over five folds and suppressing the blue emission that is otherwise observed in the conventional structure because of the excess electrons leaking towards the HTL. It is predicted in the new device structure that 97.44% of the exciton formation takes place in the QD layer, while 2.56% of the excitons form in the HTL. It is found that the enhancement in the external quantum efficiency is mainly due to the stronger confinement of exciton formation to the QDs.
  • Thumbnail Image
    ItemOpen Access
    Transition metal oxides on organic semiconductors
    (Elsevier BV, 2014-04) Zhao Y.; Zhang, J.; Liu, S.; Gao, Y.; Yang, X.; Leck K.S.; Abiyasa, A. P.; Divayana, Y.; Mutlugun, E.; Tan S.T.; Xiong, Q.; Demir, Hilmi Volkan; Sun, X. W.
    Transition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices. (C) 2014 Elsevier B.V. All rights reserved.