Two approaches are explored to improve the power conversion efficiency: (1) manipulation of the nano and microstructures and surface chemistry of the wide bandgap semiconductor oxide photoanodes with efficient quantum dots deposition and desirable internal light scattering, and (2) alignment and controlled variation of the bandgaps of quantum dots through ion exchange. For example, mesoporous TiO2 beads with combined effective light scattering effect and large surface area were prepared and studied for quantum dot-sensitized solar cell (QDSC) application. The photoanode films comprised of submicrometer-sized beads consisting of packed TiO2 nanocrystallites. A power conversion efficiency up to 4.05% has been achieved for a CdS/CdSe quantum dot (QD) co-sensitized solar cell, which was constructed with the mesoporous TiO2 beads prepared with a two-step method, in which an optimal amount of ammonia was adopted to etch TiO2 spheres and achieve desired porosity of the beads for QD adsorption. The high conversion efficiency was ascribed to a combined effect of the mesoporous structure, light scattering ability and good electrical conduction capability of the beads. ZnxCd1-xSe QDs sensitized TiO2 photoelectrodes on FTO substrates have been prepared using ion-exchange route. Lattice parameters and band gaps of such ZnxCd1-xSe QDs were found to have linear and quadratic relationships with the Zn content (x) respectively. These TiO2/ZnxCd1-xSe films were assembled to solar cells and  demonstratetractsd to be promising photoelectrodes for solar cells. In the fabricated QDs sensitized solar cells, QDs with the composition of x=0.6 produced the highest photocurrent and photoconversion efficiency. It demonstrated that the effective band alignment of QDs is favorable to enhance photovoltaic performance for solar cells, by producing an efficient electron�hole separation following a band alignment.

Engineering the microstructure and chemistry of both quantum dots and photoanodes in quantum dot sensitized solar cells for high power conversion efficiency

247th National Meeting (2014)

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