Modulations of photoinduced magnetoconductance for polymer diodes

This study elucidates the magnetoconductance (MC) response of polymer diodes, which can be modulated by photoillumination, varying the composition of the active layer and applying electrical bias. Under illumination, the short-circuit current of polymer diodes with active layers of regioregular poly(3-hexylthiophene) (P3HT) exhibits an MC response of approximately -4.0% in a magnetic field B=1000 mT at room temperature. The MC response drastically reverses from negative to positive (-23.0% to 2.0%) as the electrical bias is increased from nearly below to above the open-circuit voltage. However, it is quenched (< 0.1%) when the illumination is turned off or an electron acceptor material, [6,6]-phenyl C61-butyric acid methyl ester, is blended with P3HT as the active layer, suggesting that, in nature, the MC response is associated with the illumination and excitonic states. The annihilation of triplet excitons probably dominates the negative MC response. (C) 2008 American Institute of Physics.