溶液プロセス及び熱転写法にて作製されたポリフルオレン系高分子EL素子の発光特性改善

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.一般的なスピンコート法で作製したアモルファス相薄膜と、トルエン雰囲気中に曝露する方法や加熱基板に熱転写する方法などの成膜法を用いて作製した青色発光poly(9,9-dioctylfluorene)(PFO)や黄緑発光poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2, 1'-3 }-thiadiazole)] (F8BT)を用いた高分子有機EL素子の発光特性に関して検討を行った。PFO薄膜にはクロロホルム溶液に溶解したPFOをスピンコート法により成膜したアモルファス相薄膜、そのアモルファス相をトルエン雰囲気中に曝露してf3 相に変化させたf3相薄膜、PFOを1,2,4-トリクロロベンゼン溶液に溶解することで作製したゲル状PFO を加熱基板上に熱転写する方法で作製したf3相薄膜を用い、それぞれの高分子EL素子の発光効率を検討した結果、f3 相薄膜の高分子EL素子はアモルファス相薄膜のそれに比べ、発光効率の向上が観測された。三重項発光材料のIr錯体及びPt錯体をドープしたPFO薄膜を用いた高分子EL素子から、赤色及び近赤外燐光発光が得られ、可視及び近赤外発光高分子EL素子の作製に成功した。更に、熱転写法から作製したPFO及びPFO:F8BT薄膜を用いた高分子EL素子から偏光発光が得られた