Extremely Color-Stable Blue Light-Emitting Polymers Based on Alternating 2,7-Fluorene-co-3,9-carbazole Copolymer
✍ Scribed by Ransheng Liu; Yan Xiong; Wenjin Zeng; Zhonglian Wu; Bin Du; Wei Yang; Mingliang Sun; Yong Cao
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 191 KB
- Volume
- 208
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Novel alternating 2,7‐fluorene‐co‐3,9‐carbazole copolymer(3,9‐PFCz) was synthesized by Suzuki polycondensation between 3‐bromo‐9‐(2‐iodo‐9,9‐dioctyl‐9__H__‐fluoren‐7‐yl)‐9__H__‐carbazole and 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9‐dioctylfluorene. Cyclic voltammetry studies showed a higher HOMO level (−5.23 eV) than the polyfluorene homopolymer(PFO). The glass transition temperature of the copolymer (110 °C) was much higher than that of the PFO (67 °C). After the copolymer had been annealed at 200 °C for 2 h, the PL spectra showed almost no change and no aggregation‐ or oxidation‐related undesirable long‐wavelength emission has been observed. The light‐emitting diode in configuration of ITO/PEDOT/EML/CsF/Al showed a maximum external quantum efficiency of 1.54% with a luminance of 435 cd · m^−2^ and the maximum brightness of 2 630 cd · m^−2^ with CIE coordinate (0.17, 0.14) was achieved at 8.4 V. The device prepared in configuration of ITO/PEDOT/PVK/polymer/Ba/Al exhibits an efficient, stable blue emission; it has a turn‐on voltage of 6 V and maximum external quantum efficiency of 1.1%. The EL emission remains stable at high current density and after thermal treatment at 150 °C for 30 min. Extremely color‐stable blue emission from alternating poly[(2,7‐fluorene)‐co‐(3,9‐carbazole)] copolymer makes it a promising candidate for flat‐panel display applications.
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