RT-stable Electride and Its Application to Cold Electron Emitter and Electron Injection Layer in OLED
Electrides are ionic crystals in which electrons work as anion. However, the fatal drawback of electrides reported so far was extremely poor thermal instability, i. e. , it decomposed at -40℃ for the best material, In 2003, we fabricated roomtemperature stable electride by chemical treatment of nano-porous crystal 12CaO·7Al2O3(C12A7) with Ca metal1.C12A7, a refractory oxide (melting point 1 420℃), has a cubic lattice and a chemical formula of 2 per unit cell. The crystal is composed of sub-nanometer-sized cages which are connected 3-dimensionally by sharing open mouse. The unit cell has 2 chemical formula and may be described as Ca24 Al28 O64 4 + +2O2- , where the former and the latter denote the chemical formula of cage walls and free oxygen ions, respectively. Two free oxygen ions are randomly distributed in the cages to compensate positive charged of the walls. We synthesizedCa24 Al28 O644+ (4e- ) , a first RT-stable electride , by substituting a Free oxygen ions with 2 electrons.The resulting materials exhibit a high electrical conductivity of 1,500Scm-1 at 300 K. The work function, evaluated from electron field emission measurements is ～0.5 eV2a, which is extremely small among electron emission materials resorted so far. This material works well as a thermal field-electron emitter at ～900℃2b, which is much lower than that ( ＞1 600℃) of LaB6.The value of work function measured by UPS on fresh surfaces in UHV was 2.4 eV, which is comparable or smaller than that of an alkali metals, irrespective of high stability to atmospheric conditions. Thus, we examined this materials as the electron-injection material of OLED, finding that the barrier height of electron injection of the electride/Alq3 is ～0.6eV, which is less than half of that ( ～1.4eV) of Al/Alq3.
Hideo Hosono
Frontier Collaborative Research Center,Tokyo Institute of Technology, Nagatsuta 4259,Midori-ku, Yokohama 226-8503, Japan
国际会议
上海
英文
137-138
2007-03-12（万方平台首次上网日期，不代表论文的发表时间）