Effect of CdS nanoparticle content on the in-situ polymerization of 3-hexylthiophene-2,5-diyl and the application of P3HT‐CdS products in hybrid solar cells

Organic materials are of great interest for photovoltaic applications because of their potential low cost of production that could lead to inexpensive energy harvesting. In this paper, the synthesis and characterization of new nanocomposites of poly(3-hexylthiophene) and CdS nanoparticles (P3HT–CdS) as well as its application in a photovoltaic solar cell is demonstrated. The P3HT–CdS nanocomposites were synthesized by the direct oxidation of 3-hexylthiophene (3HT) monomers with different concentration of CdS nanoparticles. Iron chloride (FeCl3) was used as the oxidizing species for the reaction. The CdS nanoparticles were synthesized by simple solution methods. The P3HT–CdS nanocomposites were analyzed by using UV–vis spectroscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy and Thermogravimetry (TGA). SEM analyses demonstrated homogeneous distribution of the CdS nanoparticles in the P3HT. The interaction of the CdS nanoparticles with the sulfur of the thiophene rings was corroborated by FTIR. Better arrangement in the P3HT chains is also evident from the UV–vis results. Higher CdS content in the P3HT–CdS products reduces the intensity of the π–π⁎ band of the P3HT, suggesting that the polymerization of 3HT monomer could be inhibited for higher concentration of CdS nanoparticles. Hybrid photovoltaic cells based on these nanocomposites were also fabricated and evaluated. The best performance was obtained using as active layer of 3HT/CdS with a weight ratio of 1:0.5. This device showed a photocurrent (Jsc) of 1.04 mA/cm2 and a photovoltage (VOC) of 820 mV. The device was measured in air at room temperature and under 100 mW/cm2 illumination in a solar simulator.