Cadmium telluride (CdTe) photovoltaic devices fabricated by close-space sublimation have achieved power conversion efficiencies exceeding 21%, but devices fabricated from colloidal nanocrystals have yet to achieve equivalent results. The surfaces of CdTe crystal grains play an important yet poorly understood role in device efficiency; while grain boundaries lead to infamously low operating voltages, polycrystalline devices actually outperform single crystal devices. In order to study the relationship between surface and electronic structure using solution techniques, we have developed a scalable synthesis of colloidal CdTe nanocrystals from cadmium bis(phenyltellurolate) (Cd(TePh)2) and cadmium alkylcarboxylates (Cd(O2CR)2). Isolated nanocrystals have carboxylate ligands that can be displaed along with excess cadmium ions using low concentrations of L-type ligands, and using 1H NMR spectroscopy we demonstrate that the binding of Cd(O2CR)2 is 5-10 times weaker than to CdS or CdSe nanocrystals of similar size and ligand coverage. The weaker binding is proposed to arise from a lower polarity and greater stability of reconstructed CdTe surfaces.

Synthesis and surface chemistry of cadmium carboxylate passivated CdTe nanocrystals from cadmium bis(phenyltellurolate)

251st National Meeting (2016)

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