Influences of deposition and post-annealing temperatures on properties of TiO_2 blocking layer prepared by spray pyrolysis for solid-state dye-sensitized solar cells

摘要

Influences of the temperature (T_s) for spray pyrolysis deposition of TiO_2 blocking layer (BL) using titanium diisopropoxide bis(acetylacetonate) (TAA) as a precursor and the temperature (T_p) for post-annealing of the BL films on the resulting BL film morphology and photovoltaic performance of solid-state dye-sensitized solar cells (SDSC) are investigated. A T_s ranging from 300 to 400 °C is found preferable for the formation of BL films with smooth surface and dense grain packing. A T_s lower than 300 °C results in insufficient decomposition of the TAA precursor and is unable to form smooth BL films, while a T_s over 400 °C leads to loosely packed grain in BL films. Power conversion efficiency (PCE) of-4.0% is obtained for SDSC devices with BL films prepared at a T_s in the range of 300-450 °C. High temperature post-annealing (T_p =500-550 °C) of the BL films prepared at a low T_s, such as 300 °C, can improve the PCE up to 4.6%. The improvements are considered due to the higher purity, increased crystallinity, and retained high grain packing density of the post-annealed BL films, which facilitate charge transport and suppress charge recombination.