Browsing by Author "Shih, Hsi-Kang"

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A cross-linkable triphenylamine derivative as a hole injection/transporting material in organic light-emitting diodes
(2015-01-01)
Shih, Hsi-Kang
;
Chu, Yu-Lin
;
Chang, Feng-Chih
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
We have synthesized TPABZ, a new thermally cross-linkable triphenylamine derivative containing a benzoxazine functional group, for application in organic light-emitting diodes (OLEDs). We used differential scanning calorimetry, thermogravimetric analysis, UV-Vis spectroscopy, and cyclic voltammetry to investigate the thermal, physical, and electrochemical properties of TPABZ, which is readily polymerized, through ring-opening polymerization of its benzoxazine unit, upon heating at 220 degrees C for 30 min. The cured TPABZ (P-TPABZ) is suitable for use as a hole injection/transport material in OLEDs because it has an appropriate HOMO energy level (-5.16 eV) to form a stepwise energy ladder and a high LUMO energy level (-1.68 eV) with great potential for electron blocking. We fabricated multilayered OLEDs (ITO/TPABZ or P-TPABZ/NPB/Alq(3)/LiF/Al) through successive spin-coating and vacuum deposition processes; the device incorporating P-TPABZ exhibited good performance (EQE: 2.44%; LEmax: 8.42 cd A(-1); PEmax: 4.34 lm W-1).
Photo-Crosslinking of Pendent Uracil Units Provides Supramolecular Hole Injection/Transport Conducting Polymers for Highly Efficient Light-Emitting Diodes
(2015-05-01)
Shih, Hsi-Kang
;
Chen, Yi-Han
;
Chu, Yu-Lin
;
Cheng, Chih-Chia
;
Chang, Feng-Chih
A new process for modifying a polymeric material for use as a hole injection transport layer in organic light-emitting diodes has been studied, which is through 2 + 2 photodimerization of a DNA-mimetic -conjugated poly(triphenylamine-carbazole) presenting pendent uracil groups (PTC-U) under 1 h of UV irradiation. Multilayer florescence OLED (Organic light-emitting diodes) device with the PTC-U-1hr as a hole injection/transport layer (ITO (Indium tin oxide)/HITL (hole-injection/transport layer) (15 nm)/N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) (15 nm)/Tris-(8-hydroxyquinoline)aluminum (Alq(3)) (60 nm)/LiF (1 nm)/Al (100 nm)) is fabricated, a remarkable improvement in performance (Q(max) (external quantum efficiency) = 2.65%, B-max (maximum brightness) = 56,704 cd/m(2), and LE (luminance efficiency)(max) = 8.9 cd/A) relative to the control PTC-U (Q(max) = 2.40%, B-max = 40,490 cd/m(2), and LEmax = 8.0 cd/A). Multilayer phosphorescence OLED device with the PTC-U-1hr as a hole injection/transport layer (ITO/HITL (15 nm)/Ir(ppy)(3):PVK (40 nm)/BCP (10nm)/Alq(3) (40 nm)/LiF (1 nm)/Al (100 nm)) is fabricated by successive spin-coating processes, a remarkable improvement in performance (Q(max) = 9.68%, B-max = 41,466 cd/m(2), and LEmax = 36.6 cd/A) relative to the control PTC-U (Q(max) = 8.35%, B-max = 34,978 cd/m(2), and LEmax = 30.8 cd/A) and the commercial product (poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) PEDOT:PSS (Q(max) = 4.29%, B-max = 15,678 cd/m(2), and LEmax = 16.2 cd/A) has been achieved.
Ternary polybenzoxazine/POSS/SWCNT hybrid nanocomposites stabilized through supramolecular interactions
(2016)
Shih, Hsi-Kang
;
Hsieh, Chun-Cheng
;
Mohamed, Mohamed Gamal
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
In this study we linked zero-dimensional polyhedral oligomeric silsesquioxane (POSS) with one-dimensional single-walled carbon nanotubes (SWCNTs) as dual-dimensional nanohybrid complexes within polybenzoxazine matrices, stabilized through noncovalent supramolecular interactions. First, we synthesized a new bifunctionalized benzoxazine (Py-Bz-T), presenting thymine (T) and pyrene (Py) units, that displayed excellent thermal properties after thermal curing, because its T moieties increased the physical cross-linking density. Second, we prepared Py-Bz-T/OBA-POSS [octuply adenine (A)-functionalized POSS] nanocomposites and investigated, using nuclear magnetic resonance and Fourier transform infrared spectroscopies, the multiple hydrogen bonding A center dot center dot center dot T interactions between Py-Bz-T and OBA-POSS. Finally, we prepared Py-Bz-T/OBA-POSS/SWCNT ternary hybrid complexes dispersed in THF, stabilized through both multiple hydrogen bonding and pi-pi stacking interactions. Transmission electron microscopy revealed that the SWCNTs were highly dispersed and covered by the Py-Bz-T/OBA-POSS nanocomposites; these ternary hybrid complexes were stabilized through pi-pi interactions between Py-Bz-T/OBA-POSS and the SWCNTs, as evidenced using fluorescence spectroscopy.