Improved Light Emission of Polyfluorene-Type Polymer Light-Emitting Diodes by Thermal Printing and Solution Process

Kasama, Daisuke

電気材料技術懇談会

poly(9,9-dioctylfluorene)

The emission properties of polyfluorene-type polymer light-emitting diode (PLEDs), using blue emissive poly(9,9-dioctylfluorene) (PFO) and yellow-green emissive poly[9,9-dioctylfluorenyl-2, 7-diyl)-co-1,4-benzo-{2, 1'-3 }- thiadiazole)] (F8BT) fabricated by the spin-coating method, the toluene vapor method and the thermal printing method, were investigated. Poly(2, 7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene)) (TFB) is useful for buffer layer and a dopant. By using TFB as interlayer of PLED, TFB acts as exciton-blocking layer, thus prevents luminescence quenching. By using TFB with 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) as dopants of PFO, current efficiency was improved, compared to PFO only device. This result derives from these materials working as hole and electron transporting molecules. The devices with red emissive Ir complex and near-infrared Pt complex doped in PFO showed red and near-infrared phosphorescent emission, respectively. Current efficiencies of PLEDs with the~phase of PFO fabricated by the thermal printing method and the toluene vapor method were found to have better emission efficiency than that with the amorphous phase of PFO by the spin-coating method. The EL spectra of PLEDs using PFO and PFO:F8BT fabricated by the thermal printing method were polarized. It is expected to improve the characteristics of PLEDs by the optimization of the thermal printing method. We demonstrated improved light emission of PLEDs with the high-quality~phase by the thermal printing method.

Kasama, Daisuke