Carrier Transport in CdTe Nanocrystals and Coupled Films As Measured with Time-Resolved Microwave Conductivity

Wednesday, May 14, 2014: 17:20
Bonnet Creek Ballroom VI, Lobby Level (Hilton Orlando Bonnet Creek)
R. Callahan (National Renewable Energy Laboratory, University of Colorado - Boulder), R. Crisp (Colorado School of Mines, National Renewable Energy Laboratory), G. Rumbles (University of Colorado - Boulder, National Renewable Energy Laboratory), and J. Luther (National Renewable Energy Laboratory)
Solution-processable semiconducting CdTe nanocrystals are promising materials for solution processed inorganic photovoltaic technologies and other various technologies. Solution processed photovoltaic device performance is reliant on sufficient carrier transport between coupled nanocrystals.  We use transient microwave conductivity experiments to measure charge carrier mobilities within isolated CdTe tetrapods nanocrystals in solution. We find that the (GHz) mobility and lifetime of photo-induced carriers are related to the tetrapod arm dimensions. Furthermore, carrier mobilities in nanocrystal films are highly dependent on the nanocrystal capping ligand. Recent advances in inorganic ligand exchanges have allowed for coupled yet quantum-confined nanocrystal films. The combination of these experiments allows us to report photo-induced charge generation to measure both inter- and intra-NC conductivity in a series of Metal Chalcogenide capped CdTe nanocrystal films. We identify specific Te-based ligands that show transport characteristics (diffusion lengths) improved over bulk CdTe films.