Spirobifluorene derivative: a pure blue emitter (CIEy ≈ 0.08) with high efficiency and thermal stability

Abstract

A spirobifluorene derivative containing phenanthrene moiety, 2,7-di(phenanthren-9-yl)-9,9 0spirobifluorene (DPSF), has been synthesized. It shows absorption peaks at 254 nm, 310 nm, and 327 nm and a fluorescence peak at 383 nm in CHCl 3 that shifts to 398 nm in the film state. The quantum yield is 0.79 calibrated with a standard of coumarin 102 (0.93). A pure blue emission at Commission Internationale de l 0 Eclairage (CIE) (0.15, 0.08), has been achieved using DPSF as the emitter, poly(3,4ethylene dioxythiophene) : poly(styrene sulfonic acid) (PEDOT : PSS) as the hole injecting layer, 4,4 0bis[N-(1-naphthyl)-N-phenyl-amino] biphenyl (NPB) as the hole transporting layer, and 1,3,5-tris(Nphenylbenzimidazol-2-yl)-benzene (TPBI) mixing with 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) (2 : 1) as the electron transporting material. The maximum current efficiency (CE) and power efficiency (PE) of the DPSF device are 3.24 cd A À1 and 2.54 lm W À1 , corresponding to 5.41% of maximum external quantum efficiency (EQE). The spirobifluorene derivative show high thermal stabilities, 178 C for the glass transition temperature (T g ) and 503 C for the decomposition temperature (T d ). The synthesized spirobifluorene derivative shows potential application as a highly efficient pure blue emitter for organic light emitting devices (OLED).

1-Carbazolyl Spirobifluorene: Synthesis, Structural, Electrochemical, and Photophysical Properties

“…This substitution pattern drives the electronic properties of SBF compounds. The position C2 forms a para-substituted biphenyl and has significantly contributed to the development of highly efficient SBF-based materials for OE (chart 1b), mainly as emitters in blue Organic Light-Emitting Diodes (OLEDs) 3,5,[7][8][9][10][11][12] but also as electron 13 or hole 14 transporters in OLEDs and even more recently as very efficient threedimensional non-fullerene acceptors in organic solar cells. [15][16][17][18][19] The three other positions of the SBF fragment have been far less described to date but appear nevertheless highly promising to build new OSCs.…”

Highly Efficient Organic Blue Electroluminescent Materials and Devices with Mesoscopic Structures

“…Considering phenanthrene is less conjugated than anthracene, phenanthrene was introduced instead of anthracene to obtain 2,7-di(phenanthren-9-yl)-9,90-spirobifluorene (DPSF) to improve blue chromaticity (as shown in Figure 2). [28] The glass transition temperature (T g ) and the h PL in solution of DPSF are 178 8C and 0.79, respectively. The l max of the device using DPSF doped mCP as the EML was 428 nm with CIE (0.15, 0.08), very close to CIE (0.14, 0.08) of NTSC's standard blue.…”

“…A highly efficient blue emitter was designed by combining highly efficient deep blue emitting phenanthrenyl group with spirobifluorene. Considering phenanthrene is less conjugated than anthracene, phenanthrene was introduced instead of anthracene to obtain 2,7‐di(phenanthren‐9‐yl)‐9,90‐spirobifluorene (DPSF) to improve blue chromaticity (as shown in Figure ) . The glass transition temperature ( T g ) and the η PL in solution of DPSF are 178 °C and 0.79, respectively.…”

“…For blue emitters, based on the effect of molecular configuration on photoelectric properties, we proposed a promising way of combinational molecular design for a novel deep blue emitter close to the standard blue of Commission Internationale de l'É clairage (CIE) coordinates (0.14, 0.08) of National Television Standards Committee (NTSC), the device efficiency of which was beyond the theoretical limitation. [27][28][29] Considering charge transport materials, we came up with a novel strategy to develop an electron transport material (ETM) to balance carrier transport in the device, and nearly 100 % of internal quantum efficiency (h int ) has been achieved. [30][31][32][33] Investigating the coupling mechanisms of surface plasmon polaritons (SPP) and waveguide modes between free photons in OLED, the light out-coupling efficiency was dramatically improved by using a mesoscopic photonic structure.…”

“…To address these problems, there are three prime concerns to develop efficient blue OLEDs: (i) make new highly efficient blue emitters with wide E g to avoid luminescence quenching and bathochromic shift, ensuring the color purity; (ii) develop blue emitters with bipolar charge transport property and proper adjacent materials to balance carrier transport as well as confine excitons within the emitting layer (EML); (iii) utilize light out‐coupling enhancement techniques to extract light from OLEDs. For blue emitters, based on the effect of molecular configuration on photoelectric properties, we proposed a promising way of combinational molecular design for a novel deep blue emitter close to the standard blue of Commission Internationale de l′Éclairage (CIE) coordinates (0.14, 0.08) of National Television Standards Committee (NTSC), the device efficiency of which was beyond the theoretical limitation . Considering charge transport materials, we came up with a novel strategy to develop an electron transport material (ETM) to balance carrier transport in the device, and nearly 100 % of internal quantum efficiency ( η int ) has been achieved .…”