Abstract
A straight synthetic route to fabricate hybrid nanocomposite films of well-dispersed CdS nanocrystals (NCs) in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is reported. A soluble cadmium complex [Cd(SBz)2]2·MI, obtained by incorporating a Lewis base (1-methylimidazole, MI) on the cadmium bis(benzyl)thiol, is used as starting reagent in an in situ thermolytic process. CdS NCs with spherical shape nucleate and grow well below 200°C in a relatively short time (30 min). Photoluminescence spectroscopy measurements performed on CdS/MEH-PPV nanocomposites show that CdS photoluminescence peaks are totally quenched inside MEH-PPV, if compared to CdS/PMMA nanocomposites, as expected due to overlapping of the polymer absorption and CdS emission spectra. The CdS NCs are well-dispersed in size and homogeneously distributed within MEH-PPV matrix as proved by transmission electron microscopy. Nanocomposites with different precursor/polymer weight ratios were prepared in the range from 1:4 to 4:1. Highly dense materials, without NCs clustering, were obtained for a weight/weight ratio of 2:3 between precursor and polymer, making these nanocomposites particularly suitable for optoelectronic and solar energy conversion applications.
Highlights
Organic–inorganic hybrid nanocomposites have attracted great interest over recent years for their extraordinary performances due to the combination of the advantageous properties of organic polymers and the unique size-dependent properties of nanocrystals (NCs) [1,2,3]
We present a straight convenient approach to synthesize well-dispersed CdS NCs in pristine MEH-PPV using a cadmium complex obtained by incorporating a Lewis base (1-methylimidazole, methyl imidazole (MI)) on the cadmium bisthiol [19], the [Cd(SBz)2]2·MI adduct
Our studies demonstrated that annealing temperatures of about 180°C to 200°C are required for the formation of CdS NCs
Summary
Organic–inorganic hybrid nanocomposites have attracted great interest over recent years for their extraordinary performances due to the combination of the advantageous properties of organic polymers and the unique size-dependent properties of nanocrystals (NCs) [1,2,3]. CdS is considered a promising material for its Efficient photoconductivity requires efficient charge separation and efficient transport of the carriers to the electrodes without recombination, in that sense, the morphology of nanocomposite being crucial in providing suitable paths for both electron and hole towards the appropriate electrode [7]. The NC network must be homogeneous so that each negative charge can efficiently hop to another NC in the direction of the internal field, this requirement being a complex issue when NCs are dispersed in polymeric matrices. The addition of a dense network of NCs to polymers can significantly alter the mechanical properties of the resulting nanocomposite material compromising the advantageous large area composite films by spin coating, making the proposed technique not expensive and ideal to fabricate optoelectronic devices
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