Quantitative estimation of electronic quality of zinc phthalocyanine thin films

We determine the mobility-lifetime product (mu tau) of free charge carriers in pristine zinc phthalocyanine (ZnPc) films using photocurrent measurements. The photocurrent is proportional to the free charge carrier generation efficiency (eta) and the mu tau product, and the carrier collection length is directly proportional to the latter. The mu tau product is thus an important parameter for the electronic quality of a material. We further determine the dominant photocarrier generation mechanisms in ZnPc. The free carrier generation efficiency is estimated from total carrier collection and electric field-induced photoluminescence quenching measurements. Using eta and the electric field dependence of the photocurrent, we estimate the mu tau product of holes in ZnPc to be about 3x10(-11) cm(2)/V.