An effective method to prepare polymer/nanocrystal composites with tunable emission over the whole visible light range

Materials with emission over the whole visible range (400-800 nm) have been obtained through incorporating single-colored CdTe nanocrystals (NCs) into a poly(p-phenylene vinylene) (PPV) precursor [the sulfonium polyelectrolyte precursor of PPV]. Firstly, the quantum yield (QY) of the PPV precursor was improved to similar to 50% via heat treatment of a mixed solution of the PPV precursor and poly(vinyl alcohol) (PVA) at 100 degrees C for 3 min. Then, single-colored CdTe NCs were incorporated into the mixed solution. The introduction of the PVA was necessary to reduce the electrostatic interaction between the PPV precursor and CdTe NCs, which improved their compatibility. The reduced electrostatic interaction eliminated Forster resonance energy transfer (FRET) processes between NCs, as well as between NCs and the PPV precursor, which allowed the functional integration of the polymer and NCs. Consequently, polymer/NC composites with almost any Commission Internationale de L'Eclairage (CIE) coordinates can be achieved by simply changing the size and amount of the NCs. In particular, when the emission wavelength of the CdTe NCs was 559 nm, a pure white-light emitting material with CIE coordinates (0.337, 0.332) was obtained.