Role of Surface Chemistry on Charge Carrier Transport in Quantum Dot Solids

Colloidal semiconductor quantum dots (QDs) are promising materials for electronic and optoelectronic devices due to their size tunable electronic and optical properties and the solution-based processes that enable the integration of these materials into devices. However, the long, insulating ligands commonly employed in the synthesis of colloidal QDs inhibit strong interparticle coupling and charge transport once QDs are assembled into the solid state as QD arrays. A general approach to increase carrier mobility is to reduce the interparticle spacing by ligand exchange. During solution-based deposition and ligand exchange of QD thin films, the QD surfaces are often “attacked” by solvents or ligands, creating surface defect sites. These surface defects generate in-gap states that may scatter mobile carriers and reduce the lifetime of photogenerated carriers by trapping. In this talk, I will describe methods to synthetically control and spectroscopically probe the density and occupancy of defect states at the QD surface and at QD-device interfaces and their importance to creating high mobility and long lifetime QD materials for electronic and optoelectronic devices