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

The electron mobilities of tris(8-hydroxy-quinolinato) aluminum (Alq3) 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 Alq3 films. Clearly, when the thickness of Alq3 film is less than 150 nm, the electron mobilities slightly decrease with increasing the electric field. For the thickness of Alq3 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.