Colloidal Quantum Dots Intraband Photodetectors

Photoconductivity is demonstrated with monodispersed HgSe colloidal quantum dots that are illuminated with radiation resonant with 1S(e)1P(e) intraband electronic absorption, between 3 and 5 mu m. A doping of two electrons per dot gives the lowest dark current, and a detectivity of 8.5 x 10(8) Jones is obtained at 80 K. Photoluminescence of the intraband transition is also observed. The detector properties are discussed in terms of the measured photoluminescence quantum yield, the electron mobility in the 1P(e) state, and the responsivity. The intraband photoresponse allows to fully harness the quantum confined states in colloidal nanostructures, extending the prior limited use of interband transition.