Ter(9,9-diarylfluorene)s:  Highly Efficient Blue Emitter with Promising Electrochemical and Thermal Stability

Abstract

Novel ter(9,9-diarylfluorene)s were synthesized by a Suzuki-coupling reaction of 2-bromofluorene (1) and 2,7-fluorenediboronic ester derivatives (3) with high isolated yields (63-86%). The X-ray structure analysis of ter(9,9'-spirobifluorene) (4aa) revealed that the conjugated chromophore adopts a helical conformation. This conformation effectively releases the steric interaction between the fluorene moieties and prevents inter-chromophore interactions. The introduction of aryl groups at the C9 position of fluorene was highly beneficial to the thermal and morphological stability of these oligomers. These terfluorenes exhibit intense blue fluorescence with excellent quantum yields both in solution ( approximately 100%) and in solid state (66-90%), and possess interesting reversible redox properties. Highly efficient blue light-emitting OLED devices were fabricated using 4aa and 4cc as emitters as well as hole transporters. The devices exhibit low turn-on voltage ( approximately 3 V) and high EL external quantum efficiency (2.5-3%).

Electrochemistry and electrogenerated chemiluminescence of thiophene and fluorene oligomers. Benzoyl peroxide as a coreactant for oligomerization of thiophene dimers

“…S1, S2 (ESI †) and are summarized in Table 1. As these properties have already been widely investigated, [61][62][63][64][65][66] only a brief summary of the results is presented for purposes of comparison to the electrochemical and ECL results.…”

High-Contrast Tandem Organic Light-Emitting Devices Employing Semitransparent Intermediate Layers of LiF/Al/C60

“…For Device 4, NPB was commonly used as the hole transporting material. When inserting an exciton blocking layer of TPBI between the NPB layer and the cathode in Device 4, excitons were generated and locked inside the NPB layer, 19 and 5 then emitted photons through radiative transition. It is believed that the EL spectrum for Device 4 is mainly generated by the NPB layer.…”

Synthesis and Photophysical Properties of Pyrene-Based Multiply Conjugated Shaped Light-Emitting Architectures: Toward Efficient Organic-Light-Emitting Diodes

“…Because of their high photoluminescence (PL) efficiency, much research into blue-emitting materials has focused on conjugated fluorene derivatives (Yu et al, 2000;Wong et al, 2002;Kim et al, 2001), and further the introduction of aryl groups at C9 position of fluorene could improve the stability of the materials. On the other hand, as a large conjugated aromatic ring, pyrene has the advantages of high PL efficiency, high carrier mobility, and the much improved hole-injection ability than oligofluorenes or polyfluorene .…”