Incorporation of Spiroxanthene Units in Blue‐Emitting Oligophenylene Frameworks: A New Molecular Design for OLED Applications

Abstract

We report herein the incorporation of xanthenyl units into two extended π-conjugated phenylene systems, namely indenofluorene and pentaphenylene. Thus, dispiroxanthene-indenofluorene (DSX-IF) and dispiroxanthene-ladderpentaphenylene (DSX-LPP) have been designed and synthesized through short and efficient synthetic approaches. These two molecules possess a 3π-2-spiro architecture (3π-systems/2-spiro bridges), in which two xanthenyl cores are spirolinked to a π-conjugated backbone either indenofluorene for DSX-IF or pentaphenylene for DSX-LPP. The structural, electrochemical, and photophysical properties of these blue/violet emitters have been studied in detail and compared to those of their 'all carbon' analogues with spirofluorenyl cores instead of spiroxanthenyl cores, namely dispirofluorene-indenofluorene (DSF-IF) and dispirofluorene-ladderpentaphenylene (DSF-LPP), previously reported in the literature. Finally, the application of DSX-IF and DSX-LPP as new light-emitting materials in nondoped organic light emitting diodes is reported. A detailed optical study of the different electroluminescence spectra is notably presented, with an emphasis 1) on the origin of the low-energy emission band observed in the case of DSX-LPP and 2) on the unexpected optical contribution of the well-known hole-transporting-layer NPB (N,N'-di(naphtyl)-N,N'-diphenyl(1,1'-biphenyl)-4,4'-diamine).

Structure–property relationship of 4-substituted-spirobifluorenes as hosts for phosphorescent organic light emitting diodes: an overview

“…The overall yield of the approach B, ie 46%, is lower than that of the approach A (83%), 70 but uses as key intermediate the versatile 4-bromo-fluorenone 5. This molecule can be a useful building block to synthesize other families of OSCs constructed on the 4-fluorene scaffold such as dicyanovinylene, 73,74 spiroxanthene, 75,76 spirothioxanthene, 77 spirophenylacridine, 60, 61 spiroindoloacridine 63 and quinolinophenothiazine 62 derivatives. Fluorenone 5 has also been synthesized by Ma et al using a different route (Figure 4, bottom).…”

Electron-Deficient Dihydroindaceno-Dithiophene Regioisomers for n-Type Organic Field-Effect Transistors

“…The exponential development of organic electronic leads to an always growing demand of new, highly efficient organic semiconductors (OSCs) adapted to their use in specific devices 1 including organic light-emitting diodes (OLED) based on fluorescent emitting materials, [2][3][4][5][6][7][8] or based on phosphorescent materials, [9][10][11][12][13][14][15][16][17][18][19] organic field-effect transistor (OFET) [20][21][22][23][24] or organic photovoltaic (OPV). 1,25 Historically, in the field of OFETs, the design of p-type materials (hole-transporting) such as pentacene, 26 oligothiophene 27 or bridged oligoarylene [28][29] 33 (see 1-4 structures in Chart 1).…”

4-Pyridyl-9,9′-spirobifluorenes as Host Materials for Green and Sky-Blue Phosphorescent OLEDs

“…In this context, numerous efficient blue fluorophores have been designed for the last twenty years and used as emitting layer in OLED. [5][6][7][8][9][10][11] However, the research towards highly efficient OLEDs using fluorescent materials has quickly pointed out the limit of this technology due to its maximum achievable internal quantum yield (IQE) of 25 % (which correspond to 5% of an external quantum efficiency (EQE) without enhancement of light out-coupling). 12,13 Significant progress has been made with the host-3 guest phosphorescent OLED technology for which IQE of 100 % (EQE ca 20%) may be theoretically reached.…”