Organic semiconductor composites: Influence of additives on the transient photocurrent

We report on the effect of various guest molecules added to a functionalized anthradithiophene (ADT) host on photoexcited charge carrier dynamics in solution-deposited thin films, from ∼100 ps to >100 μs after photoexcitation with 100 fs laser pulses. An addition of 2 and 5 wt % of C60 to a fluorinated ADT derivative, ADT-TES-F, resulted in transient photocurrent amplitude enhancement by a factor of ∼3 and 10, respectively. In contrast, an addition of 10 wt % of another ADT derivative, ADT-TIPS-CN, or a functionalized pentacene derivative (TIPS pentacene) to ADT-TES-F led to a decrease in the amplitude by a factor of ∼3–4 and dramatically different photocurrent dynamics.