Thin films of inorganic nanocrystals have shown potential as the active layers of photovoltaic devices.  The solution processing of these structures takes advantage of the solubility of the as-prepared nanocrystals in organic solvents, enabling low temperature processing methods such as spin, spray, or dip coating to be used.  The resulting films range from 50 to 500 nm in thickness.  At this stage, removal of the nanocrystal surface ligands is a critical processing step, as electron transport through the device is inhibited by the separation between inorganic cores.  Several strategies exist for addressing this issue.  In the case of CdTe nanocrystals, a sintering treatment consisting of exposure to CdCl2 followed by annealing at 400 oC has been shown to effectively remove ligands and increase the grain size of the inorganic film, increasing current densities several orders of magnitude to >10 mA/cm2.  Low temperature alternatives that do not increase the grain size would be advantageous, as quantum confinement effects could then be maintained in the system.  In this direction, several small molecule ligand exchange treatments have been examined in addition to the incorporation of one dimensional nanorod and nanowire structures.  The ligand substitution was monitored using FTIR spectroscopy, and the resulting films characterized by SEM and profilometry.  The impact of these treatments on the device IV behavior will also be presented.

Inorganic nanocrystal films for photovoltaics

244th National Meeting (2012)

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