Efficient M-shaped blue emitters having a high conjugation extent with improved roll-off efficiency

Abstract

We have synthesized M-shaped acceptor-donor-acceptor (A-D-A) materials namely, TPA-2SPPITPA and TPA-2PPITPA consist of two identical π-conjugated groups. Both TPA-2SPPITPA (Td/Tg, °C: 582/219) and TPA-2PPITPA (Td/Tg, °C: 543/209) exhibit excellent thermal...

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“…Jayabharathi et al 161 reported the preparation of M-shaped TPA-2SPPITPA/TPA-2PPITPA emitters with the twist angle of absorption at a longer wavelength and the absorption onset became red-shifted compared to Ph-BPA-BPI due to the stronger ÀI ability of pyrene than phenanthrene. In polar solvent, a hypsochromic shift of 14 nm was observed for Py-BPA-BPI due to the formation of the TICT state and LE state in the aggregated solid due to the restricted intramolecular rotation [T g , T d : 196 The smaller injection barrier facilitated efficient h + and e À injection into the EML@low V. The BOLEDs [ITO/NPB (70 nm)/ TCTA (5 nm)/Ph-BPA-BPI/Py-BPA-BPI (30 nm)/TPBI (40 nm)/LiF (1 nm)/Al (150 nm)] showed the EL of 448/471 nm; CE of 3.60/ 10.9 cd A À1 ; PE of 3.66/10.5 lm W À1 ; EQE of 4.56/5.64%; EUE of 36.2/39.2%; and CIE of (0.15, 0.08)/(0.17, 0.29), respectively.…”

“…Jayabharathi et al 161 reported the preparation of M-shaped TPA-2SPPITPA/TPA-2PPITPA emitters with the twist angle of 25.89° between TPA and SPPI of TPA-2SPPI (TPA-2SPPITPA) and 30.76° between TPA and PPI (TPA-2PPITPA) does not affect the conjugation between D (TPA) and A (PPI) and it is adequate to construct the HLCT state with proper coupling of LE with CT. The effective h + and e − overlap for TPA-2SPPITPA than TPA-2PPITPA increased the oscillator strength of TPA-2SPPITPA compared to TPA-2PPITPA.…”