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RGB Small Molecules Based on a Bipolar Molecular Design for Highly Efficient Solution‐Processed Single‐layer OLEDs
Author(s) -
Yao Liang,
Xue Shanfeng,
Wang Qi,
Dong Wenyue,
Yang Wei,
Wu Hongbin,
Zhang Ming,
Yang Bing,
Ma Yuguang
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201101476
Subject(s) - carbazole , materials science , oled , pedot:pss , luminescence , optoelectronics , electroluminescence , layer (electronics) , solution process , diode , analytical chemistry (journal) , photochemistry , nanotechnology , chemistry , organic chemistry
In this paper, we describe a bipolar molecular design for small molecule solution‐processed organic light emitting diodes (OLEDs). Combining the rigidity of the conjugated emissive cores and the flexibility of the peripheral alkyl‐linked carbazole groups, two series of highly efficient bipolar RGB (red, green, blue) emitters have been synthesized and characterized. The emissive cores are composed of electron‐withdrawing groups; the carbazole groups endow the materials electron‐donating units. Such bipolar structures are advantageous for the carrier injection and balance. Four peripheral carbazole groups are introduced in T‐series materials (TCDqC, TCSoC, TCBzC, TCNzC), and another four in O‐series materials (OCDqC, OCSoC, OCBzC, OCNzC). With the single‐layer device configuration of ITO/PEDOT:PSS/emitting layer/CsF/Al, two green devices exhibited excellent performance with a maximum luminescence efficiency of over 6.4 cd A −1 , and a high maximum luminance of more than 6700 cd m −2 . In addition, compared with the T‐series, the luminescence efficiency of blue and red devices based on O‐series materials increased from 1.6 to 2.8 cd A −1 and 0.2 to 1.3 cd A −1 , respectively. To our knowledge, the performance of the blue device based on OCSoC is among the best of the blue small‐molecule solution‐processed single‐layer devices reported so far.