Remote doping of a pentacene transistor: Control of charge transfer by molecular-level engineering

We demonstrate that holes from a p-doped N, N′ -diphenyl- N, N′ -bis(1-naphthyl)- 1, 1′ -biphenyl- 4, 4′ -diamine (α -NPD) layer transfer to an adjacent pentacene film. The spatial separation of carriers from dopants, or remote doping, is demonstrated with a combination of photoemission spectroscopy and current-voltage measurements for a p-doped α -NPD/pentacene heterojunction. Increased conductivity of the pentacene film is observed in both nongated temperature-dependent conductivity and gated thin-film transistor measurements.