Photodetectors and Photovoltaic Devices Based on Semiconductor Nanomaterials

Photodetectors based various nanostructures and plasmon enhanced solar cells are investigated in this dissertation. The motivation of the dissertation rise is driven by urgent need of both high efficiency photodetectors and solar cells. First, quantum dot infrared photodetectors have been intensely investigated due to their promise in high performance photodetectors. However, the strain-driven growth of quantum dots has hindered the progress of quantum dot photodetectors. The presence of strain in the device presents complexity in designing as well as defects. Therefore, in this project, new designs of quantum dot photodetector structures are presented to improve the control over detection wavelength. Moreover, strain-free nanomaterials are incorporated in the photodetectors for the first time in order to replace conventional strained quantum dots. By using the novel designs and nanomaterials, multicolor photodetector has been demonstrated. Based on these studies, high efficiency photodetectors may be achieved. Second, the increasing energy consumption of limited natural energy resources has brought urgent requirement of sustainable and renewable energy resources. Solar energy directly from the Sun is promising in solving current energy crisis. In order to serve as a primary energy source, solar energy has to be harvested efficiently and be cost effective. Therefore, increasing the conversation efficiency beyond current technologies is high priority in current photovoltaics field. In this project, surface plasmonic effects are investigated for possible application in high efficiency quantum dot solar cells. Quantum dots have been widely used to implement high efficiency intermediate band solar cells. Due to the low absorption in quantum dots, the performance of quantum dot solar cells has been unsatisfying. In this dissertation, potential applications of surface plasmon in implement of intermediate band solar cell are experimentally studied. Significantly, overall conversion efficiency of quantum dot solar cell has been improved for over 2%. More importantly, further enhancement is expected after optimization of design of plasmonic quantum dot solar cells. This dissertation provides a way to effectively harvest the solar energy in the infrared wavelength region