Synthesis and electroluminescent studies of blue-emitting copolymers containing phenylene vinylene and oxadiazole moieties in the main chain

Two statistical copolymers III and IV combining features of the two reference polymers I and II were synthesized by a Wittig reaction with the objective of raising the electron-transport properties and fluorescence quantum yields relative to the alternating block copolymers I and II. The electroluminescent properties of singlelayer LEDs using these copolymers were studied. External quantum efficiencies of 0.035 and 0.11% were obtained from single-layer devices on the basis of III and IV, respectively, which are higher than those of similar devices using I and II. Two single-layer LEDs using a blend of I and II (4:1 and 1:1 wt/wt) corresponding to the compositions of copolymers III and IV, respectively, were also fabricated for comparison. Results indicated that the covalent incorporation of oxadiazole is effective in improving the efficiency of LEDs and that the molar content of oxadiazole plays an important role in the performance of the devices. (C) 2001 John Wiley & Sons, Inc.