Optimizing LED Properties of 2,7-Bis(phenylethenyl)fluorenes
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- 作者：Hemali P. Rathnayake ; Ali Cirpan ; Paul M. Lahti ; and Frank E. Karasz
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：January 24, 2006
- 年：2006
- 卷：18
- 期：2
- 页码：560 - 566
- 全文大小：155K
- 年卷期：v.18,no.2(January 24, 2006)
- ISSN：1520-5002
文摘
(E,E)-2,7-Bis(3,4,5-trimethoxyphenylethenyl)fluorene, 1, and a segmented copolymer 2 composed ofthe same chromophore alternated with nonconjugated 1,6-hexanediyl (alt-oligo(2,6-dimethoxylphenylene-4-vinylene-[9,9-diethylfluoren-2-yl-7-vinylene]-3,5-dimethoxy-phenylene-4-[1,6-hexanedioxyl]) were synthesized. They have solution photoluminescence emission maxima at 420-460 nm, with quantumefficiencies of 0.93 and 0.68, respectively, in chloroform. Electroluminescent spectra in an LEDconfiguration ITO/PEDOT-PSS/(1 or 2)/Ca-Al both showed maxima at 470-480 nm, although thespectrum from 2 was significantly broader. The luminance of LEDs with 1 was over 10-fold higher thanthose with copolymer 2, 0.515 versus 0.040 cd/A, with turn-on voltages of 3 and 5 V, respectively. Thecrystallography of 1 showed no chromophore 
-stacking; this absence should limit tendencies for emissionwavelength shifts due to solid state interchromophore interactions. When 1 was heated in air beforeincorporation into an LED emissive layer, a 540 nm emission component was produced, which did notoccur if 1 was not heated before use. Emissive layers of 1 with PMMA gave stronger luminance thaneither neat 1 or 2, with only a modest increase in turn-on voltage. A 10% (w/w) 1:PMMA based LEDemission showed a maximum at 444 nm (blue emission with CIE color coefficients of (0.153,0.312)),with a luminance efficiency of 4.5 cd/A and a turn on voltage of 4.5 V.
-stacking; this absence should limit tendencies for emissionwavelength shifts due to solid state interchromophore interactions. When 1 was heated in air beforeincorporation into an LED emissive layer, a 540 nm emission component was produced, which did notoccur if 1 was not heated before use. Emissive layers of 1 with PMMA gave stronger luminance thaneither neat 1 or 2, with only a modest increase in turn-on voltage. A 10% (w/w) 1:PMMA based LEDemission showed a maximum at 444 nm (blue emission with CIE color coefficients of (0.153,0.312)),with a luminance efficiency of 4.5 cd/A and a turn on voltage of 4.5 V.