Facile synthesis and application of hyperbranched TiO2 hollow spheres for enhancement of power conversion efficiency of CdSeTe quantum dot-sensitized solar cells

In this research TiO2 hollow spheres (HSs) were prepared using hydrothermally grown carbon spheres as the templates through a sol gel, liquid phase deposition method followed by an annealing process. Then they were introduced to another hydrothermal process for a controlled growth of the TiO2 branches on their surface. The synthesized branched HSs were deposited on a nanocrystalline TiO2 sublayer and formed an effective light scattering film in the photoelectrode of corresponding quantum dot sensitized solar cells (QDSCs). This could majorly increase the light traveling path inside the light absorbing quantum dots sensitizing layers and increase the power conversion efficiency. Three types of photoelectrodes including TiO2 NCs/CdSeTe sensitizing QDs/ZnS, TiO2 NCs/TiO2 HSs/CdSeTe QDs/ZnS and TiO2 NCs/TiO2 branched HSs/CdSeTe QDs/ZnS were fabricated and applied in QDSCs. The alloyed CdSeTe quantum dots (QDs) were synthesized through organometallic approach in high temperature with an absorption edge located around 800 nm. The corresponding bandgap energy is consequently appropriate for light absorption in visual-near IR region. The selection of hyperbranched TiO2 HSs with different dimensions of branches was so carried out to make the maximum QDs loading. Based on the findings, thepower conversion efficiency of the QDSC with TiO2NCs/TiO2 HSs/CdSeTe photoanode was measured about 4.8