TY - JOUR
T1 - The effects of ultra-thin cerium fluoride film as the anode buffer layer on the electrical characteristics of organic light emitting diodes
AU - Lu, Hsin Wei
AU - Tsai, Cheng Che
AU - Hong, Cheng Shong
AU - Kao, Po Ching
AU - Juang, Yung Der
AU - Chu, Sheng Yuan
N1 - Funding Information:
This work was supported by the Industrial Technology Research Institute of Taiwan .
Publisher Copyright:
© 2016 Elsevier B.V. All rights reserved.
PY - 2016/11/1
Y1 - 2016/11/1
N2 - In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF 3 film as an ultra-thin buffer layer between the indium tin oxide (ITO) electrode and α-naphthylphenylbiphenyldiamine (NPB) hole transport layer, with the structure configuration ITO/CeF 3 (0.5, 1, and 1.5 nm)/α-naphthylphenylbiphenyl diamine (NPB) (40 nm)/tris(8-hydroxyquinoline) aluminum (Alq 3 ) (60 nm)/lithium fluoride (LiF) (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone treated CeF 3 film. The work function increased from 4.8 eV (standard ITO electrode) to 5.22 eV (0.5-nm-thick UV-ozone treated CeF 3 film deposited on the ITO electrode). The surface roughness of the UV-ozone treated CeF 3 film was smoother than that of the standard ITO electrode. Further, the UV-ozone treated CeF 3 film increased both the surface energy and polarity, as determined from contact angle measurements. In addition, admittance spectroscopy measurements showed an increased capacitance and conductance of the OLEDs. Accordingly, the turn-on voltage decreased from 4.2 V to 3.6 V at 1 mA/cm 2 , the luminance increased from 7588 cd/m 2 to 24760 cd/m 2 , and the current efficiency increased from 3.2 cd/A to 3.8 cd/A when the 0.5-nm-thick UV-ozone treated CeF 3 film was inserted into the OLEDs.
AB - In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF 3 film as an ultra-thin buffer layer between the indium tin oxide (ITO) electrode and α-naphthylphenylbiphenyldiamine (NPB) hole transport layer, with the structure configuration ITO/CeF 3 (0.5, 1, and 1.5 nm)/α-naphthylphenylbiphenyl diamine (NPB) (40 nm)/tris(8-hydroxyquinoline) aluminum (Alq 3 ) (60 nm)/lithium fluoride (LiF) (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone treated CeF 3 film. The work function increased from 4.8 eV (standard ITO electrode) to 5.22 eV (0.5-nm-thick UV-ozone treated CeF 3 film deposited on the ITO electrode). The surface roughness of the UV-ozone treated CeF 3 film was smoother than that of the standard ITO electrode. Further, the UV-ozone treated CeF 3 film increased both the surface energy and polarity, as determined from contact angle measurements. In addition, admittance spectroscopy measurements showed an increased capacitance and conductance of the OLEDs. Accordingly, the turn-on voltage decreased from 4.2 V to 3.6 V at 1 mA/cm 2 , the luminance increased from 7588 cd/m 2 to 24760 cd/m 2 , and the current efficiency increased from 3.2 cd/A to 3.8 cd/A when the 0.5-nm-thick UV-ozone treated CeF 3 film was inserted into the OLEDs.
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U2 - 10.1016/j.apsusc.2016.05.105
DO - 10.1016/j.apsusc.2016.05.105
M3 - Article
AN - SCOPUS:84971290239
VL - 385
SP - 139
EP - 144
JO - Applied Surface Science
JF - Applied Surface Science
SN - 0169-4332
ER -