今春に修士修了した 加藤哲也君 (Mr. Tetsuya Kato) の共役高分子電解質とポリアミンのブレンドからなる電子注入層を用いた有機EL素子に関する「Conjugated Polyelectrolyte Blend with Polyethyleneimine Ethoxylated for Thickness-Insensitive Electron Injection Layers in Organic Light-Emitting Devices」と題する研究論文が アメリカ化学会 の ACS Applied Materials & Interfaces (IF: 7.50) に受理されました。電子輸送性骨格を持つ共役高分子電解質と電子注入性に優れるポリアミンを混合して電子注入層として応用したところ、低電圧かつ膜厚への依存性が小さい電子注入層を実現できました。論文中では、ブレンド膜中における高分子の分散状態も含めて議論しました。一緒に実験を進めてくれた林幸宏君、高橋達弥君、鈴木道法君、おめでとう！本研究は SPring-8 の小金澤博士に GIWAXD 実験を、オーストラリア Monash 大学の Christopher R. McNeil 准教授に NEXAFS 実験をご協力いただきました。
By Satoru Ohisa,* Tetsuya Kato, Tatsuya Takahashi, Michinori Suzuki, Yukihiro Hayashi, Tomoyuki Konganezawa, Christopher R. McNeil, Takayuki Chiba, Yong-Jin Pu, Junji Kido,*
ACS Applied Materials & Interfaces, in press.
Abstract: Electron injection layers (EILs) based on a simple polymer blend of polyethyleneimine ethoxylated (PEIE) and poly[(9,9-bis(3'-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN-Br) can suppress the dependence of organic light-emitting device (OLED) performance on thickness variation compared with single PEIE or PFN-Br EILs. PEIE and PFN-Br were compatible with each other, and PFN-Br uniformly mixed in the PEIE matrix. PFN-Br in PEIE formed more fluorene–fluorene pairs than PFN-Br alone. In addition, PEIE:PFN-Br blends reduced the work function (WF) substantially compared with single PEIE or PFN-Br polymer. PEIE:PFN-Br blends were applied to EILs in fluorescent polymer-based OLEDs. Optimized PEIE:PFN-Br blend EIL-based devices presented lower driving voltages and smaller dependences of device performance on EIL thickness than single PEIE or PFN-Br-based devices. These improvements were attributed to electron-transporting fluorene moieties, increased fluorene–fluorene pairs working as channels of electron transport, and the large WF reduction effect of PEIE:PFN-Br blends.
