Quantitative estimation of electronic quality of zinc phthalocyanine thin films

Abstract

We determine the mobility-lifetime product (\ensuremath{\mu}\ensuremath{\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 (\ensuremath{\eta}) and the \ensuremath{\mu}\ensuremath{\tau} product, and the carrier collection length is directly proportional to the latter. The \ensuremath{\mu}\ensuremath{\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 \ensuremath{\eta} and the electric field dependence of the photocurrent, we estimate the \ensuremath{\mu}\ensuremath{\tau} product of holes in ZnPc to be about 3\ifmmode\times\else\texttimes\fi{}10${}^{\ensuremath{-}11}$ cm${}^{2}$/V.