Our interest in colloidal semiconductor quantum dots (QDs) stems from their size-tunable properties, unique photophysics (e.g., multiple exciton generation), and ability to be self-assembled from solution into functional films for optoelectronics. Our work is vertically integrated, encompassing QD synthesis, film fabrication via self-assembly, ligand and surface chemistry studies, structural characterization, fundamental investigations of charge transport using a variety of experimental approaches (field-effect transistors, Hall effect), and fabrication, characterization and modeling of QD-based devices such as solar cells, photodetectors and transistors. A major goal of the QD sub-group is to fabricate QD solids with sufficient spatial and energetic order to trigger the emergence of electronic mini-bands that offer high carrier mobility and long diffusion length with controlled doping, as is necessary for making high-performance QD optoelectronic devices.
The slide above summarizes some of our ongoing work in this field. The videos below show (left) the conversion of an oleate-capped PbSe QD superlattice into an epitaxially-fused superlattice and (right) an electron tomography reconstruction of a 120 × 38 nm disc-shaped region of a PbSe QD epi-superlattice at 0.65 nm resolution.
Collective topo-epitaxy in the self-assembly of a 3D quantum dot superlattice.
Abelson, A., Qian, C., Salk, T., Luan, Z., Fu, K., Zheng, J.-G., Wardini, J. L., Law, M. Nature Materials, 19, 49-55 (2020) PDF Online Article
Structural characterization of a polycrystalline epitaxially-fused colloidal quantum dot superlattice by electron tomography.
Chu, X., Heidari, H., Abelson, A., Unruh, D., Hansen, C., Qian, C., Zimanyi, G., Law, M., Moule, A. J. Journal of Materials Chemistry A, 8, 18254 (2020) PDF Online Article
Dynamic deformability of individual PbSe nanocrystals during superlattice phase transitions.
Wang, Y., Peng, X., Abelson, A., Xiao, P., Qian, C., Yu, L., Ophus, C., Ercius, P., Wang, L.-W., Law, M., Zheng, H. Science Advances, 5, eaaw5623 (2019) PDF Online Article
PbSe quantum dot field-effect transistors with air-stable electron mobilities above 7 cm2 V-1 s-1.
Liu, Y., Tolentino, J., Gibbs, M., Ihly, R., Perkins, C. L., Liu, Y., Crawford, N., Hemminger, J. C., Law, M. Nano Letters, 13, 1578-1587 (2013) PDF Online Article
Robust, functional nanocrystal solids by infilling with atomic layer deposition.
Liu, Y., Gibbs, M., Perkins, C. L., Zarghami, M. H., Bustamante, Jr., J., Law, M. Nano Letters, 11, 5349-5355 (2011) PDF Online Article
Dependence of carrier mobility on nanocrystal size and ligand length in PbSe nanocrystal solids.
Liu, Y., Gibbs, M., Puthussery, J., Gaik, S., Ihly, R., Hillhouse, H. W., Law, M. Nano Letters, 10, 1960-1969 (2010) PDF Online Article
Emergence of distinct electronic states in epitaxially-fused PbSe quantum dot superlattices.
Kavrik, M. S., Hachtel, J., Ko, W., Qian, C., Abelson, A., Unlu, E. B., Kashyap, H., Li, A.-P., Idrobo, J.-C., Law, M. Preprint (2021) Online Article