Application of TiO₂ with different structures in solar cells

The application of TiO₂-based devices is mainly dependent on their crystalline structure, morphology, size, and exposed facets. Two kinds of TiO₂ with different structures, namely TiO₂ pompons and TiO₂ nanotubes, have been prepared by the hydrothermal method. TiO₂ with different structures is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer—Emmett—Teller (BET) surface area analysis. Solar cells based on poly(3-hexylthiophene) (P3HT) and TiO₂ with different structures are fabricated. In the device ITO/TiO₂/P3HT/Au, the P3HT is designed to act as the electron donor, and TiO₂ pompons and TiO₂ nanotubes act as the electron acceptor. The effects of the TiO₂ structure on the performance of hybrid heterojunction solar cells are investigated. The device with TiO₂ pompons has an open circuit voltage (V_oc) of 0.51 V, a short circuit current (J_sc) of 0.21 mA/cm², and a fill factor (FF) of 28.3%. Another device with TiO₂ nanotubes has a V_oc of 0.5 V, J_sc of 0.27 mA/cm², and FF of 28.4%. The results indicate that the TiO₂ nanotubes with a unidimensional structure have better carrier transport and light absorption properties than TiO₂ pompons. Consequently, the solar cell based on TiO₂ nanotubes has a better performance.