Heterojunction photovoltaics using printed colloidal quantum dots as a photosensitive layer.

We demonstrate a bilayer photovoltaic device consisting of a heterojunction between colloidal cadmium selenide (CdSe) quantum dots (QDs) and a wide band gap organic hole-transporting thin film of N,N'-diphenyl-N,N'-bis(3-methylphenyl)[1,1'-biphenyl]-4,4'-diamine (TPD) molecules. The active light-absorbing film of QDs is nondestructively printed onto TPD using microcontact stamping. Indium-tin-oxide (ITO) provides the top contact. The resulting device structure can accommodate different size QDs, produces an exceptionally large open circuit voltage (0.8 V) for an architecture with symmetric electrodes, and yields an internal quantum efficiency of 10% at the first QD absorption peak.