2019年3月修士修了の鈴木道法君と大久哲助教の電子注入ポリマーへのイオン化合物添加による有機EL素子への電子注入性制御に関する「Doping of Tetraalkylammonium Salts in Polyethylenimine Ethoxylated for Efficient Electron Injection Layers in Solution-Processed Organic Light-Emitting Devices」と題する論文が米国化学会 (ACS) の ACS Applied Materials & Interfaces (IF: 8.097) に受理されました！
Title: Doping of Tetraalkylammonium Salts in Polyethylenimine Ethoxylated for Efficient Electron Injection Layers in Solution-Processed Organic Light-Emitting Devices
By S. Ohisa*, M. Suzuki, T. Chiba, J. Kido*, ACS Appl. Mater. Interfaces, 2019, in press.
Abstract: For efficient electron injection, a method to control the work functions (WFs) of ZnO electrodes in organic light-emitting devices (OLEDs) was reported in this study. First, ZnO was modified by the doping of tetraalkylammonium salts (TRAX) into polyethylenimine ethoxylated (PEIE) for the WF control. Tetrabutylammonium salts (TBAX), where X = chloride, bromide, iodide, acetate, thiocyanate, and tetrafluoroborate anions, were doped into PEIE. A WF of non-doped PEIE-modified ZnO was3.65 eV, whereas TBAX-doped PEIE-modified ZnO exhibited WFs ranging from 3.52 eV to 3.00 eV depending on the anion. TBAX salts exhibited different electron-donating capabilities depending on the anion, and the doping of TBAX with a large electron-donating capability exhibited a large WF reduction effect. In addition, tetraethyl- and tetrahexyl-ammonium chlorides were doped into PEIE. PEIE doped with TRACl containing long alkyl chains exhibited a large WF reduction effect due to their low electron-accepting capabilities. In addition, the WF reduction mechanism was considered by the depth direction analysis of the PEIE:TBAX films. Finally, the ZnO/PEIE:TRAX bilayers were applied as electron injection layers in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] emissive-layer-based OLEDs with an inverted structure. The ZnO/PEIE:TBAX devices with low WFs exhibited low driving voltages.