Dye sensitization is an important technique to increase the spectral photoresponse in high bandgap semiconductors, which are more stable in photo-electrochemical cells. However, these devices have low quantum efficiencies and poor stability. One of the most serious problems is the concentration quenching in which absorbed photon energy is dissipated as heat energy due to the segregation of dye molecules. The only way to suppress concentration quenching is to devise a method of dispersing dye molecules on the surface, minimizing the formation of aggregates. Within this proposal, the investigators will develop devices and material processing technologies necessary to prevent segregation of dye molecules by the molecular self-assembly method. The preliminary investigations in this project will demonstrate the feasibility of this technology.
The investigators will employ the self-assembling techniques to insert dye molecules into a few monolayers of nanoporous material grown on the semiconductor surface. Two types of prototype devices will be investigated. First, a photodetector will be fabricated by depositing a conductive and transparent metal oxide film on the surface and second, a photo-electrochemical cell will be prepared by immersing the dye-coated electrode in an electrochemical cell. The structure, surface properties, photocurrent, quantum efficiency and optical properties of the devices will be measured and simulated. It is anticipated that these types of self-assembly methods can be widely used in many other applications, such as in molecular devices, nanoscale biosystems, and nanoelectronics.
The broader impact of this project includes (i) undergraduate and graduate research, (ii) participation in a high school outreach program by delivering a seminar, and (iii) building the foundation for a nanotechnology course in the college. Two undergraduate students and two full time graduate students will be involved in carrying out the experimental work. Every effort will be made to involve students from diverse background in nanotechnology.
