"Hitherto, it has been reported that TiO2-based DSSCs achieved a notable PCE of over 14%... However, further improvements in PCE are difficult to achieve due to some disadvantages in current TiO2-based DSSCs, such as the low carrier transportation rate of TiO2 resulting from its low electron mobility, as well as the difficulty in fabricating TiO2 nanostructures with a large surface-to-volume ratio..."