Open-Circuit Voltage Loss In Annealed P3ht: Perylene Diimide Bulk Heterojunction Solar Cells

Solar cells based on blends of regioregular poly(3-hexylthiophene) as a donor and a commercial perylene diimide derivative as a acceptor are investigated. Thermal annealing of the devices results in increased photocurrent generation but is simultaneously accompanied by a loss in open-circuit voltage. It is shown that the decreased open-circuit voltage is caused by the formation of a cathode barrier, as evidenced by injection-limited electron currents, a reduced built-in voltage, and a weaker light-intensity dependence of the open-circuit voltage. Device simulations show that the increased photocurrent after annealing is the result of an increased electron mobility. Published by AIP Publishing.