Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Chemistry

Supervisor

John F. Corrigan

2nd Supervisor

Yining Huang

Joint Supervisor

Abstract

Nanoscale semiconductors have emerged as alternative candidates for the absorber layer in solar cells. Group 11-13-16 semiconductors have received a lot attention because of their direct band gap energies, high absorption coefficients and environmental friendly nature. To date, CuInS2, CuInSe2 and AgInS2 semiconductors are three of the main ternary nanomaterials investigated. Besides the application in solar cells, these nanoscale semiconductors can also be applied in areas such as biosensors and hydro catalysis.

However, it is often challenging to prepare small-sized nanoparticles with uniform size and shape, especially for large scale production. In this thesis, the synthesis of CuInS2, CuInSe2 and AgInS2 nanomaterials were probed by using single source precursors via one-step solvothermal reaction. Single source precursors were applied to control the composition, shape and size without the need of balancing the stoichiometric ratio, which is also a challenge for the fabrication of ternary semiconductors. Solvothermal methods can take full advantage of the reaction pressure and simplify the traditional routes for crystallization. Various conditions were investigated including different precursors, reaction temperatures, times and secondary chalcogen source. After optimizing the conditions, products were controlled in a form of wurtzite structure with tunable sizes in a range of 2 to 5 nm, which ultimately tunes the band gap energy. Especially for CuInSe2 nanoparticles, the band gap was successfully tuned to 1.62 eV versus 1.04 eV of bulk CuInSe2, which made this material to be more efficient to generate an exciton pair under exposure to visible light instead of infrared light. In addition, quantum yields of emission for these nanoparticles experienced a slight increase compared to the previously published work, approaching 11.5 % for CuInS2 and 19.0 % for CuInSe2. Also, powder X-ray diffraction, electron microscopy and optical spectroscopy were used to characterize the structures and optical properties.

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