TY - JOUR
T1 - Improved efficiency of polymer light-emitting diodes by inserting a hole transport layer formed without thermal treatment above glass transition temperature
AU - Shakutsui, Masato
AU - Matsuura, Hiromi
AU - Fujita, Katsuhiko
N1 - Funding Information:
We would like to express sincere thanks to Prof. Tetsuo Tsutsui for helpful discussions, and Sumitomo Chemical Co., Ltd. for supplying the TFB and F8BT available for our use. This work was supported by a grant from the Global-Center of Excellence in Novel Carbon Resource Sciences, Kyushu University and by KAKENHI (21350102).
PY - 2009/8
Y1 - 2009/8
N2 - We have demonstrated a significant improvement in the performance of polymer light-emitting diodes (PLEDs) by inserting the fluorene-triatylamine copolymer as hole transport layer (HTL) without a thermal treatment above the glass transition temperature (Tg). A thin HTL insolubilized by a thermal treatment above Tg is often inserted as an interlayer between an anode buffer layer and a light-emitting polymer (LEP) in PLEDs fabricated by using a conventional solution process. The evaporative spray deposition using ultradiluted solution (ESDUS) method has enabled fabricating polymer bilayer structure without an insolublizing procedure. The bilayer PLEDs fabricated by ESDUS without the thermal treatment showed significantly higher and more stable external quantum efficiency than PLEDs having the conventional interlayer. Thermal treatment above Tg of the copolymer would induce degradation of its hole injection property. Furthermore, ESDUS bilayer devices showed much higher power efficiency than interlayer devices when calcium was used for cathode. The improvements would be caused by the enhancement of hole injection and the effective electron blocking at the copolymer/LEP interface in the ESDUS bilayer devices.
AB - We have demonstrated a significant improvement in the performance of polymer light-emitting diodes (PLEDs) by inserting the fluorene-triatylamine copolymer as hole transport layer (HTL) without a thermal treatment above the glass transition temperature (Tg). A thin HTL insolubilized by a thermal treatment above Tg is often inserted as an interlayer between an anode buffer layer and a light-emitting polymer (LEP) in PLEDs fabricated by using a conventional solution process. The evaporative spray deposition using ultradiluted solution (ESDUS) method has enabled fabricating polymer bilayer structure without an insolublizing procedure. The bilayer PLEDs fabricated by ESDUS without the thermal treatment showed significantly higher and more stable external quantum efficiency than PLEDs having the conventional interlayer. Thermal treatment above Tg of the copolymer would induce degradation of its hole injection property. Furthermore, ESDUS bilayer devices showed much higher power efficiency than interlayer devices when calcium was used for cathode. The improvements would be caused by the enhancement of hole injection and the effective electron blocking at the copolymer/LEP interface in the ESDUS bilayer devices.
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U2 - 10.1016/j.orgel.2009.04.004
DO - 10.1016/j.orgel.2009.04.004
M3 - Article
AN - SCOPUS:67649233087
VL - 10
SP - 834
EP - 842
JO - Organic Electronics: physics, materials, applications
JF - Organic Electronics: physics, materials, applications
SN - 1566-1199
IS - 5
ER -