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A Series of Energy‐Transfer Copolymers Derived from Fluorene and 4,7‐Dithienylbenzotriazole for High Efficiency Yellow, Orange, and White Light‐Emitting Diodes
Author(s) -
Zhang Lianjie,
Hu Sujun,
Chen Junwu,
Chen Zhenhui,
Wu Hongbin,
Peng Junbiao,
Cao Yong
Publication year - 2011
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201100844
Subject(s) - materials science , quantum efficiency , fluorene , electroluminescence , copolymer , photoluminescence , chromophore , oled , photochemistry , polymer , luminous efficacy , analytical chemistry (journal) , optoelectronics , nanotechnology , composite material , layer (electronics) , organic chemistry , chemistry
Eight random and alternating copolymers PF‐DTBTA derived from 2,7‐fluorene and 4,7‐dithienylbenzotriazole (DTBTA) were synthesized. Thin solid films of the energy‐transfer copolymers possess high absolute photoluminescence (PL) quantum yields ( Φ PL ) between 60−72%. Inserting PVK layer between anode and emissive layer could show higher electroluminescence (EL) performances due to PVK‐enhanced hole injection. Random copolymers PF‐DTBTA1−15, with DTBTA molar contents from 1% to 15%, displayed yellow EL spectra with high external quantum efficiency (EQE max ) up to 5.78%. PF‐DTBTA50, the alternating copolymer, showed an orange EL with EQE max of 3.3%. The good Φ PL and EQE max of the PF‐DTBTA50 with very high DTBTA content indicate that DTBTA is a high efficiency chromophore with very low concentration quenching effects in the solid state PL and EL processes. PF‐DTBTA0.03−0.1 could emit white EL due to partial energy transfer from fluorene segments to DTBTA units. Moreover, white EL devices, with forward‐viewing maximum luminous efficiency up to 11 cd/A and stable white EL spectra (CIE coordinates of (0.33, 0.43)) in high current range from 5 mA to 60 mA, could be realized from the non‐doped polymer with simple binary structure. Our results suggest that DTBTA has big potential to construct high performanced EL polymers or oligomers.