Highly improved light harvesting and charge separation of TiO2/N719 photoanodes using surface NiTiO3 quantum dot decoration

Conventional TiO2/N719 photoanodes often suffer from the limited visible light absorption (450-500 nm) and the serous recombination of photo-generated carries (e(-)/h(+))/electrolyte ions (I-3(-)), accordingly outputting a low photoelectronic conversion efficiency (PCE). In this work, a type of strawberry-like TiO2/NiTiO3 (NTO) nanospheres was designed via a simple hydrothermal method. In this design, the NTO quantum dots (QDs) with size of several nanometers were decorated on the surface of TiO2 nanospheres. This TiO2/NTO nanostructure can not only enhance the visible light absorption of the TiO2/N179 photoanodes but also improve the separation of photo-generated carriers and depress the recombination of e(-)/h(+) and I3-. Thus, the optimal TiO2/NTO/N719 dye-sensitized solar cells (DSSCs) achieved greatly improved Jsc and Voc, both of which result into a 32.8%-improved PCE compared to the TiO2/N719 ones. These improvements could be due to the decreased charge transfer resistance at the photoanode/electrolyte interface (R-ct2) and the increased electron lifetime (tau(n)) caused by TiO2/NTO hetero-interface. In addition, the optimization on NTO QDs indicates that the density of QDs main affects the tau(n), and the size of QDs affects with R-ct2. Moderate density and size (ca. 5 nm) of QDs can optimize the photoelectronic performances of DSSCs.

Automated summary

By decorating NTO quantum dots on the surface of TiO2 nanospheres, the TiO2/NTO nanostructure enhances visible light absorption, improves the separation and recombination of photo-generated carriers, resulting in significantly improved photoelectronic conversion efficiency of DSSCs.