title: RGB small molecules based on a bipolar molecular design for highly efficient solution-processed single-layer OLEDs.
abstract: 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.
authors.affiliation: Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130012, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Yao
authors.forename: Shanfeng
authors.initials: S
authors.lastname: Xue
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Wenyue
authors.initials: W
authors.lastname: Dong
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Hongbin
authors.initials: H
authors.lastname: Wu
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.forename: Bing
authors.initials: B
authors.lastname: Yang
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Ma