Lateral organic bilayer heterojunction photoconductors

We demonstrate a two-terminal, lateral organic bilayer photoconductor that generates an external quantum efficiency of (12 +/- 1)%, with an internal quantum efficiency of (140 +/- 2)% indicative of photon-to-electron conversion gain. The photoconductor incorporates a heterojunction between N,N'-bis(3-methylphenyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (TPD) and 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI). Excitons generated with photoexcitation of PTCBI dissociate at the PTCBI/TPD interface and raise the charge carrier concentration in TPD, increasing device conductance. The exposed top surface enables interaction with chemical analytes in the environment, motivating the use of the photoconductor as a chemical sensor that transduces chemical signals into amplified changes in the electrical response. (C) 2008 American Institute of Physics.