Interband and intraband optical studies of CdSe colloidal nanocrystal films

Abstract

We present results for optical measurements on charged CdSe nanocrystals. The injection of electrons into quantum confined states is confirmed by monitoring changes in the visible and infrared absorption spectra. Interestingly, the response is observed only in the nanocrystals that have been chemically treated with sodium biphenyl. Bleaching of the visible interband transition is observed upon electron injection into the nanocrystal films. It is expect that, with injected electrons in the 1S[e] state, more electrons are available to undergo the intraband transition and absorb more light in infrared region. However, the opposite effect is observed. The energy and cross section of the infrared absorption are consistent with a one-electron transition between the 1S[e] and 1P[e] states confined in the quantum dots.