The effect of photoanode structure on the performances of quantum-dot-sensitized solar cells: a case study of the anatase TiO2 nanocrystals and polydisperse mesoporous spheres hybrid photoanodes

TiO2 polydisperse mesoporous spheres (PMSs) and nanocrystals were selectively prepared via slightly altering the precursor dosage in a solvothermal reaction. Afterwards, the submicrometer-sized PMSs and nanocrystals were adopted as sample materials to shed light on the effect of the photoanode structure over the performance of CdS/CdSe-cosensitized solar cells by comparing four types of photoanode structures: nanocrystal film, blend film, bilayer film and PMSs film. It was found that the bilayer photoanode could promote the harvesting of incident light by increasing both the CdS/CdSe QDs loading amount and the scattering effect. According to the transient photovoltage measurements, the carrier recombination at the TiO2/electrolyte and FTO/electrolyte interfaces were substantially passivated in the bilayer cell. Moreover, a high electron diffusion rate of 142.0 x 10(-9) m(2) s(-1) was also obtained in the bilayer cell, indicating high photoelectrons collection efficiency in the film structure. Therefore, the bilayer cell can well integrate the structural advantages of the PMSs and nanocrystals, which contributes to a high conversion efficiency of 4.70%, demonstrating a similar to 54% and similar to 12% improvement compared with the cells derived from nanocrystal and PMSs, respectively.