Tunneling conduction in dense silicon quantum dot/poly (methyl methacrylate) composites

The conduction mechanism of organically passivated silicon quantum dots (SiQDs) embedded in Poly(methyl methacrylate) (PMMA) has been investigated. This architecture forces the charge carriers onto the QDs, eliminating the need for charge transfer between the host matrix PMMA and the SiQDs. Octene was determined to be the shortest aliphatic ligand for electroluminescent films, as mixtures of 5:1 SiQDs:PMMA were readily synthesized without precipitation. At low fields, the current is limited by space charge effects with a weak temperature dependence which is believed to be due to the quantum dot size distribution. The lack of a temperature dependence on the current-voltage characteristics in the high voltage regime suggests that trap assisted tunneling is the primary conduction mechanism rather than transport through the PMMA. An analysis of the results suggests that the tunneling effective mass in PMMA is approximately 0.23m_o. Thus, preparing SiQDs in a PMMA matrix may yield a recombination pathway for generated excitons allowing for the creation of efficient light emitting devices.