Enhancing the electroluminescence properties of novel blue light emitting polymer and MEH-PPV based white light emitting polymer devices by processing condition optimization

Abstract

A series of triarylaminooxadiazole-containing tetraphenylsilane light emitting polymer (PTOA) and poly(2-methoxy, 5-(2′-ethyl-hexyloxy)-p- phenylene-vinylene) (MEH-PPV) based white light emitting polymer devices (PLEDs) were fabricated to study blue and orange-red emitter composition and light emitting layer processing effects on white emission electroluminescence properties. Color purity, current turn-on voltage, brightness, and current efficiency were strongly determined by MEH-PPV content and the thin film processing condition. The intensity of PTOA blue emission was equal to that of MEH-PPV orange-red emission when the device was fabricated by a polymer composite film containing 10 wt % of MEH-PPV. Color purity [Commission Internationale de L'Eclairage (CIEx,y) coordinates (0.26,0.33)] was nearly white emission under applied 8 V. The brightness and current efficiency of PTOA-MEH-PPV composite film based devices increased as MEH-PPV content increased. Furthermore, white emission blue shifted with increasing spin-rate of thin film coating and applied voltage. Low turn-on voltage, high current density, and high brightness were obtained for the device fabricating with light emitting layer coating with high spin-rate. Moreover, low current efficiency was obtained for the PLED with a thinner light-emitting layer. A white emission CIE (0.28,0.34) was obtained for PTOA-MEH-PPV based white PLED. White PLED brightness and efficiency can be as high as 700 cd/m2 and 0.78 cd/A, respectively. © 2007 Wiley Periodicals, Inc.