High-stability Ti4+ precursor for the TiO2 compact layer of dye-sensitized solar cells.

A compact layer (blocking layer) can effectively block the direct contact between the fluorine-doped tin oxide (FTO) glass substrate and electrolyte in dye-sensitized solar cells (DSSCs). The TiCl 4 hydrolysis has been widely adopted for preparing the TiO 2 compact layer (H-TiO 2 ). However, the TiCl 4 aqueous solution is unstable for its high reactivity. To improve the chemical stability of TiCl 4 aqueous solution, the Ti 4+ is encapsulated by the polymer, polyethyleneimine (PEI). Experimentals show that the Ti-PEI precursor solution can maintain their initial performances for several months. The resulting TiO 2 film (P-TiO 2 ) grown by the Ti-PEI precursor is dense, smooth and uniform without any visible and detectable cracks or voids. The P-TiO 2 compact layer is even denser than the H-TiO 2 compact layer, suggesting reducing the electron recombination and prolonging the electron lifetime in dye-sensitized solar cells. Indeed, the electron lifetime of the DSSC based on the P-TiO 2 is 13.15 ms, which is longer than the 10.83 ms based on H-TiO 2 . Meanwhile, the power conversion efficiency of the DSSC based on P-TiO 2 compact film is about 12.5% higher than that based on H-TiO 2 . Therefore, this encapsulation technology can not only improve the stability of the metal ions solution but also meet a large-scale fabrication demand of the TiO 2 compact layer in future DSSCs. [ABSTRACT FROM AUTHOR]