Improving P3HT:PCBM absorber layers by blending TiO2/CdS nanocomposites for application in photovoltaic solar cells

In this work we propose the use of the semiconducting TiO2/CdS nanocomposite (NC) to improve the optical and electrical properties of the P3HT:PCBM polymeric system employed as the absorber layer in organic photovoltaic solar cells. Therefore, we report a methodology for obtaining the TiO2/CdS-NC, its incorporation into precursor solutions containing P3HT and PCBM polymers, and the fabrication of hybrid P3HT:PCBM:TiO2/CdS-NC absorber layers. The effect of the mass ratio between the TiO2/CdS-NC and the polymeric system was studied. XRD measurements conducted on the TiO2/CdS-NC showed that the TiO2 component has a tetragonal crystalline structure (anatase phase) with a nanocrystalline size of 15.8 nm, while the CdS component has the hexagonal close-packed crystalline structure with a nanocrystalline size of 14.9 nm. XPS analysis confirmed the formation of stoichiometric TiO2 and CdS compounds. The formation of any other compound comprising the elements Ti, O, Cd and S was not found, however, elements Cl, Br, N and C were observed at trace levels, which come from the capping agent that was used to obtain the nanocomposite. Measurements on the hybrid P3HT:PCBM:TiO2/CdS-NC absorber layers through UV-vis spectroscopy showed a shift on the absorption edge and an improved light absorption for wavelengths below 550 nm. The four-point probe measurements showed a decrease of the electrical resistivity from 8.5 x 10(8) omega-cm in pristine P3HT:PCBM to a minimum of 4 x 10(5) omega-cm in the hybrid absorber layers. Both the light absorption and the electrical resistivity are modulated by the mass ratio between the TiO2/CdS-NC and the P3HT:PCBM polymeric system.

Automated summary

This study proposed the use of TiO2/CdS nanocomposite to enhance the optical and electrical properties of the P3HT:PCBM polymeric system in organic photovoltaic solar cells, showing improved light absorption and decreased electrical resistivity in hybrid absorber layers. XRD and XPS analysis confirmed the formation of TiO2 and CdS compounds, with measurements indicating modulated light absorption and electrical resistivity by the mass ratio between TiO2/CdS-NC and the polymeric system.