The local energy level of polyimide

Photoconduction and photoabsorption experiments on polyimide films with different imidities and crosslinking densities are described. Initially the energy gap was found to be larger than 10.35 eV, and the thresholds of photoinjection for gold and aluminium electrodes were 1.65 eV and 0.9 eV, respectively. By changing the molecular morphology of the sample, changing the polarity of the radiated electrode, and precharging the sample under high voltage, it was shown that there are many kinds of local energy levels with different energy levels in the forbidden band. Local levels were found to be closely related to the chemical and physical morphology of the material, among which the level originating from the imide group is the deepest level and acts as an electron donor. The density of the remaining levels decreases with the increase of imidity and crosslinking density