GENERATION AND DRIFT OF PHOTOCARRIERS IN A CONJUGATED LADDER POLYMER

Generation and drift of photocarriers in thin films of the conjugated ladder polymer, poly(benzimidazobenzophenanthroline) (BBL), are explor ed by using transient photoconductivity methods. An estimation of a lo wer limit for photogeneration efficiency of mobile holes is found to b e close to 10(-2) at an electric field of 5 X 10(5) V/cm. The drift of photogenerated carriers is found to be severely range limited by trap ping events. In addition persistent decay of photocurrent is detected following the termination of a steady-state monochromatic illumination . The form of the persistent photocurrent suggests a broad range of re lease times of the trapped carriers which can be attributed to a disor der-induced distribution of trapping sites.