It can also decouple the contradictory demand in bare TiO2 film between fast charge transport which desires heavy doping and less electron recombi-nation which desires light doping [2], because the light-injected electrons from the TiO2-dye interface in F-T DSCs only need to traverse a ultra thin layer of TiO2 prior to being extracted by the highly conductive FTO core via a drift-assisted transport [7] instead of diffusive transport [8] in bare TiO2 DSCs (a slow mechanism with electron escape times of 1-10 ms for 10-mm-thick TiO2 films) photoanodes.
At the same time, due to the difference of Fermi levels between FTO (approximately 4.8 eV vs Evac) and TiO2 (approximately -4.4 eV vs Evac) [2,10], electrons flowing from TiO2 to FTO layer in F-T photoanode results in band bending [11,12] of TiO2