329 HWAHAK KONGHAK Vol. 39, No. 3, June, 2001, pp. 329-332
(Journal of the Korean Institute of Chemical Engineers)
†
(2001
Color Change by Controlling Carrier Recombination Zone for Organic Light Emitting Devices
Sungsoo Lee and Sung M. Cho†
Department of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Korea (Received 26 January 2001; accepted 26 April 2001)
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Abstract−In order to investigate the carrier recombination zone in organic light emitting devices, three different color- emitting(R, G, B) materials are inserted in series between a hole transport layer(HTL) and an electron transport layer(ETL). For controlling the carrier recombination zone and changing the emission wavelength, α-NPD is used as a electron blocking layer to limit the electron transport in the devices. It was found that the recombination zone moved as the applied voltage changed in case of no electron blocking layer used. When the electron blocking layer α-NPD was used, the green emission was observed since the electron transport was limited by α-NPD. In this study, it was shown that the emission color could be controlled by aligning HOMO and LUMO energy bands of organic light emitting materials.
Key words: Organic Light Emitting Devices, Recombination Zone, HTL, ETL
†E-mail: smcho@skku.ac.kr
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331
HWAHAK KONGHAK Vol. 39, No. 3, June, 2001
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332
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Fig. 4. The CIE chromaticity coordinate as the applied voltage changes;
(a) structure (I), (b) structure (II), (c) structure (III).
