One-dimensional semiconductor wires with lengths longer than micrometers can efficiently absorb light that in turn generates mobile charge carriers within the semiconductor. When the diameters of these materials become small, on the order of nanometers to tens of nanometers, both the colors of the light that are preferentially absorbed and the energies of the charge carriers within the semiconductor material can be manipulated. These one-dimensional materials are called semiconductor nanowires, and they represent the smallest structures that can efficiently generate and transport charges along specific directions. The main goal of this interdisciplinary research project is to characterize the efficiency of semiconductor nanowires in terms of charge-carrier generation and transport. An emphasis is placed on optimizing the chemical and physical properties of semiconductor nanowires so their viability in application designs can be evaluated. The research uses both traditional optical spectroscopy and advanced laser techniques to probe the energies of the charge carriers within the nanowires and to characterize the fate of these charge carriers as a function of time and position along single nanowire. Particular attention is given to measuring how well the charge carriers are transported along the length of the nanowires. Another focus of this project is on training the next generation of scientists, especially those from underrepresented backgrounds with diverse expertise in materials science, chemistry, and physics.
This research is focused on optimizing the properties of semiconductor quantum wires synthesized by using the solution-liquid-solid strategy with a particular focus on cadmium telluride and cadmium selenide quantum wires. The research team is performing absorbance and photoluminescence spectroscopy experiments to characterize the energies of charge carriers photo-generated within them as well as the photoluminescence quantum yields of the these nanostructures. The dynamics of the electrons, holes, and excitons within the quantum wires are characterized by performing photoluminescence lifetime and transient absorption spectroscopy experiments. Specific goals include: 1) characterization of the exciton lifetime dependences on photoluminescence quantum yield, surface passivation and structural quality of the quantum wires; 2) measurement of exciton diffusion length along single quantum wires and its dependence on photoluminescence quantum yield, surface passivation and quantum wire structural quality; and 3) investigation of the apparent competition between efficient exciton diffusion and the probability for radiative recombination within the quantum wires.
