Two novel poly(aryl ether)s consisting of alternate isolated chromophores, poly[oxy-[9-(2-ethylhexyl)carbazole-3,6-oxy]-3,3‘ ‘‘-dicyano-p-quaterphenyl-4,4‘ ‘‘-ylene] (PCNCA) and poly[oxy-[9-(2-ethylhexyl)carbazole-3,6-oxy]-3,3‘ ‘‘-bis(trifluoromethyl)p-quaterphenyl-4,4‘ ‘‘-ylene] (PCFCA), have been
synthesized and characterized. The synthesized polymers are completely soluble in common organic
solvents such as tetrahydrofuran (THF) and chloroform. The two poly(aryl ether)s exhibit good thermal
stability with 5% weight loss temperature above 400 °C in nitrogen. The UV/vis and photoluminescent
spectra of the two polymers show maximum peaks at around 318−319 and 407−413 nm in the film state,
respectively. The HOMO and LUMO energy levels of these polymers, which have been measured by cyclic
voltammetry, are −5.23, −3.25 eV for PCNCA and −5.41, −3.32 eV for PCFCA. The p-quaterphenyl
segments are regarded as electron transporting units because the electron withdrawing substitutes (cyano
and trifluoromethyl) enhance the electron affinity. On the contrary, the carbazole segments act as hole
transporting units. The two units could decrease the barriers of charge injection from opposite electrodes.
Furthermore, all of the two units are emissive chromophores so the photoluminescence (PL) of polymers
resulted from the two units. The relative quantum yields of the two polymers are respectively 0.02, 0.40
in film state, and 0.04, 0.19 in THF for PCNCA, PCFCA.
We have developed highly efficient white top-emitting organic light-emitting devices (TOLEDs) with broad emission by modifying both anode and cathode. To alleviate the undesirable microcavity effect and obtain "broad" white emission, CF xcoated Ag anode with modified reflectivity and an index-matching layer (SnO 2 ) capped on thin Ca/Ag cathode with a maximal transparency of 80% were employed. A top-emitting broad white light device based on the dual layer architecture of light blue and yellow emitters with one of the highest EL efficiencies of 22.2 cd/A (9.6 lm/W) at 20 mA/cm 2 and 7.3 V with Commission Internationale d'Eclairage (CIE) coordinates of (x=0.31, y= 0.47) has been demonstrated.
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