Synthesis of CdS nanocrystals in poly(3-hexylthiophene) polymer matrix: optical and structural studies

CdS nanocrystals (NCs) were directly synthesized in P3HT matrix by decomposition of single-molecule precursor compound. In this process, a molecular precursor solution was mixed with the polymeric solution. On heating the solution to the decomposition temperature of the precursor compound, NCs were formed in situ at temperatures as low as 120 degrees C. The effects of the precursor concentration on the optical properties of the composite were studied. The results showed evidence of charge transfer and size variation depending on NCs concentration. CdS phase can be formed using this process at 120 degrees C temperature as was evident from the X-ray diffraction studies. Transmission electron microscope results confirm formation of monodispersed CdS nanoparticles of average size 4 nm. A possible mechanism of the CdS film formation was also investigated. UV-Vis measurements show that these CdS composites possess a direct band gap energy higher than 2.45 eV depending on the concentration of P3HT, indicating that the nano size can be controlled by the concentration of polymer additive in the composite. A higher concentration of P3HT showed more blue shift.