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Extremely Color‐Stable Blue Light‐Emitting Polymers Based on Alternating 2,7‐Fluorene‐ co ‐3,9‐carbazole Copolymer
Author(s) -
Liu Ransheng,
Xiong Yan,
Zeng Wenjin,
Wu Zhonglian,
Du Bin,
Yang Wei,
Sun Mingliang,
Cao Yong
Publication year - 2007
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200700212
Subject(s) - fluorene , carbazole , polyfluorene , copolymer , pedot:pss , electroluminescence , materials science , glass transition , oled , cyclic voltammetry , condensation polymer , polymer chemistry , polymer , quantum efficiency , photochemistry , thermal stability , chemistry , optoelectronics , nanotechnology , organic chemistry , electrochemistry , composite material , electrode , layer (electronics)
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.