Composition-limited spectral response of hybrid photovoltaic cells containing infrared PbSe nanocrystals

We report the effects of composition on the performance, particularly the spectral response, of hybrid photovoltaic cells made of PbSe nanocrystal quantum dot (NQD)/poly-3(hexylthiophene) nanocomposites. Photocurrent measurements under monochromatic and white light illuminations were employed to characterize devices consisting of thin nanocomposite films with different NQD weight percentages. It was found that at different illumination wavelengths, the short-circuit current of the hybrid device responds diversely to the variation in the NQD loading. The finding is correlated to the optical and morphological properties of the nanocomposite films, which can be further linked to the absorption and carrier-transport properties. In addition, the observed power dependence of photocurrent on intensity has revealed the pseudomonomolecular recombination kinetics in the NQD-polymer nanocomposite, indicating that the efficiency of the hybrid photovoltaic cells can be enhanced by reducing the potential barriers formed by ligand molecules at the nanocrystal surfaces. (C) 2008 American Institute of Physics.