Effect of polymer matrix on a reversible light-induced change in charge acceptance and retention of molecularly doped polymers

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Abstract
We have studied the effects of a polymer matrix on charge acceptance and retention of polymers doped with hole-transport molecules in order to understand the nature of traps in molecularly doped polymers (MDPs). Prolonged illumination decreases charge acceptance and retention of MDPs. A light-induced change in charge acceptance depends on the kind of polymer binder. A remarkable change is observed in acidic polymer binders or basic polymer binders exhibiting broad absorption spectra. In MDPs manifesting a remarkable light-induced change, the transient photocurrent pulse shape becomes dispersive after prolonged light exposure. The experimental results show that the shallow charge emission centers increase during light exposure. These shallow charge emission centers are metastable states formed by charge transfer between the transport molecule and the polymer matrix during light exposure.