Photoconduction in Alq3 -: art. no. 123704

Photoelectronic properties of Alq(3) were studied by photoconductivity (PC) measurements in thin film, sandwich (indium-tin-oxide/Alq(3)/LiF/Al) devices. We find that the photocurrent is dominated by bulk generation of carriers for incident photon energies greater than 2.75 eV. The quantum efficiency of photocarrier generation has been measured from carrier collection measurements to be about 10%. The quantum efficiency is largely independent of electric field. This enables a direct measurement of the electric field dependence of mobility using photoconductivity measurements, which is used for quantitative analysis of the dark forward current in these devices. PC measurements were also used to obtain (mu(0n)tau(n)) product which can be used as a measure of material quality. For Alq(3), we find that the value of (mu(0n)tau(n)) product was between 3x10(-15) cm(2)/V to 8x10(-15) cm(2)/V for different samples. In forward bias, at high field the photocurrent shows saturation accompanied by a phase shift. These effects are attributed to space charge effects in the device. (c) 2005 American Institute of Physics.