No abstract

A series of triarylaminooxadiazole-containing tetraphenylsilane light emitting polymer (PTOA) and poly(2-methoxy, 5-(2 0 -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 (CIE x,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/m 2 and 0.78 cd/A, respectively.

A series of polymer light emitting devices (PLEDs) based on the composite films of N-arylbenzimidazoles trimer (TPBI), poly (n-vinylcarbazole) (PVK), and a triarylaminooxadiazole-containing tetraphenylsilane light emitting polymer (PTOA) were investigated. Electroluminescence (EL) performance is enhanced with doped TPBI into the light-emitting layer for the PTOA-based devices. A deep blue emission (Commission Internationale de L'Eclairage (CIE x,y ) corodinates (0.16,0.06)) is obtained for the TPBI-PTOA-based device. Brightness and current efficiency of the TPBI-PTOA-based device can be as high as 961 cd/m 2 and 1.85 cd/A, respectively. The EL performances of TPBI-PTOA composite film-based devices are further enhanced by inserting a TPBI layer into the light emitting layer and cathode interface for a better electron and hole charge balance. Doping TPBI into the light-emitting layer of PVK-PTOA is not favorable for enhanced EL performances. Brightness and current efficiency reduced with increasing TPBI content for the TPBI-PVK-PTOA-based devices. Similar results are obtained for devices based on the TPBI-PVK-PTOA/TPBI bi-layer composite solid film. Morphology and charge balance effects on EL performances of TPBI-PTOA and TPBI-PVK-PTOA composite films based PLEDs are discussed in detail.