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Molecular Linker to Quantum Dots Sensitized Solar Cells

Molecular Linker to Quantum Dots Sensitized Solar Cells

The functionalization of nanostructured titanium dioxide and zinc oxide for solar cell applications using dyes has been studied extensively.  Since their discovery, the drive has been to improve the efficiency, as the cost of production is very low compared to conventional Si-based cells.  Recently dyes based on organic perovskite materials achieved efficiencies of 15 % in laboratory tests.  One way to improve the effectiveness of these dye-sensitized cells is to replace the dye with quantum dots (QDs) where multiple exciton generations (MEG) can occur.  Here essentially we obtain two (or more) electrons for each photon of sunlight absorbed.

However, in order to ensure efficient charge transfer from the quantum dots to the metal oxide suitable “linker molecules” are required, which are capable of forming strong bonds to both the dot and the oxide,  whilst having molecular orbitals at energies capable of capturing the excited electrons from the excited state of the dot and transferring them to the conduction band of the n-type metal oxide.  In addition to this, the functional groups should bond selectively to either the QD or the oxide surface and in an ordered manner in order to maximize the coverage of the dots on the oxide surface. This project will study the interaction between molecules, which are believed to have the properties above.

Carboxylic acids are well known to bond strongly to titanium dioxide and zinc oxide surfaces and amines to materials such as lead sulphide which are being investigated for MEG.  Also,  it has been found that  CdSe,  CdTe core shell structures can be capped with chloride containing ligands so the project will also investigate chloro-benzoic acid  as a  potential anchor.

The project will chiefly utilize x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy to characterize the molecule/nanoparticle/QD interaction, but there will also be some opportunities to carry out synchrotron radiation and laser-based surface analysis techniques.

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