Determination of electron mobility in tris(8-hydroxy-quinolinato) aluminum by admittance spectroscopy

摘要

The electron mobilities of tris(8-hydroxy-quinolinato) aluminum (Alq_3) thin films at various thicknesses (70-280 nm) have been determined by using admittance spectroscopy measurements. Our results show that the electric field dependence of electron mobilities exhibits different behaviors at different thicknesses of Alq_3 films. Clearly, when the thickness of Alq_3 film is less than 150 nm, the electron mobilities slightly decrease with increasing the electric field. For the thickness of Alq_3 film more than 150 nm, however, the mobilities increase as the electric field increases. The phenomena are well discussed by energetic disorder. Using temperature dependent Ⅰ-Ⅴ characteristics, we further calculated the density of traps.