Efficient top-emitting polymeric white light-emitting diodes with improved charge-injection

 

論文發表人：李卓澔(加州大學洛杉磯分校材料科學暨工程學系)

 

http://www.mrs.org/s_mrs/sec.asp?CID=7605&DID=186909

 

研究發現經由改善陽極與陰極介面，可以獲得高效率、上發光式之白光高分子發光二極體。在相當低的電流密度下(1.2 毫安培/平方公分)，最高效率可以達到11.42 流明/瓦，而顏色座標則顯示在位置 CIE(X=0.35, Y=0.43)。元件結構包含陽極/LEP/陰極，LEP意即是高分子發光材料，在本研究當中採用poly(9,9-dioctylfluorene) 並參雜 0.2 wt% Rubrene。結果發現在陽極與陰極的介面當中添加一層超薄的電洞注入層(HTL)和電子注入層(ETL)，電子電洞的注入效率呈現顯著的提高。經由光電轉換量測指出效率的提升是來自於電洞躍遷能障的降低，而能障的降低則是由於電洞注入層的添加。

 

Efficient top-emitting polymeric white light-emitting diodes has been realized by improving charge-injection from both anode and cathode contacts. The device has a structure of anode/LEP/cathode, where light-emitting polymer (LEP) is poly(9,9-dioctylfluorene) doped with 0.2 wt% rubrene. It has been found that charge injection was significantly enhanced by adding an ultrathin electron-injection layer (EIL) and hole-injection layer (HIL) into cathode and anode, respectively. Mechanism study with photovoltaic measurement indicates that improved hole-injection is due to the reduction of barrier height, resulted from the addition of HIL. Peak power efficiency of 11.42 lm/watt was achieved at current density 1.2 mA/cm² with the Commission International de L'Eclairage (CIE) coordinates of (x=0.35, y=0.43).