Efficient dye-sensitized charge separation in a wide-band-gap <i>p</i>-<i>n</i> heterojunction

Abstract

We report the fabrication and performance of a dye-sensitized p-n heterojunction formed from a planar interface between two wide-band-gap semiconductors, n-TiO2 and p-CuSCN, which contains an intervening monolayer of a sulforhodamine B dye. When exposed to visible light, the photoexcited dye molecules transfer electrons to the n-TiO2 and holes to the p-CuSCN. The absorbed-photon-to-current efficiency (APCE) is ≳70% and the open circuit voltage is ≊500 mV. This heterojunction is the solid-state analog of the dye-sensitized photoelectrochemical interfaces used in photography and photovoltaics. The high quantum efficiency and voltage show that it is possible to simultaneously optimize both the dye/n-type and dye/p-type interface for efficient forward charge injection and slow charge combination in a solid-state device.