Development of III-Sb Quantum Dot Systems for High Efficiency Intermediate Band Solar Cells
- Univ. of California, Los Angeles, CA (United States)
- Rochester Inst. of Technology, NY (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
This project aimed to develop solar cells that can help reduce cost per watt. This work focused on developing solar cells that utilize quantum dot (QD) nanomaterials to provide multijunction solar cell efficiency at the cost of single junction solar cell. We focused on a novel concept known as intermediate band solar cells (IBSC) where an additional energy band is inserted in a single solar cell to accommodate sub-bandgap photons absorption which otherwise are lost through transmission. The additional energy band can be achieved by growing QDs within a solar cell p-n junction. Though numerous studies have been conducted to develop such QD systems, very small improvements in solar energy conversion efficiency have been reported. This is mainly due to non-optimal material parameters such as band gap, band offset etc. In this work, we identified and developed a novel QD material system that meets the requirements of IBSC more closely than the current state-of-the-art technology. To achieve these goals, we focused on three important areas of solar cell design: band structure calculations of new materials, efficient device design for high efficiency, and development of new semiconductor materials. In this project, we focused on III-Sb materials as they possess a wide range of energy bandgaps from 0.2 eV to 2eV. Despite the difficulty involved in realizing these materials, we were successfully developed these materials through a systematic approach. Materials studied in this work are AlAsSb (Aluminum Arsenide Antimonide), InAlAs (Indium Aluminum Arsenide) and InAs (Indium Arsenide). InAs was used to develop QD layers within AlAsSb and InAlAs p-n junctions. As the QDs have very small volume, up to 30 QD layers been inserted into the p-n junction to enhance light absorption. These QD multi-stack devices helped in understanding the challenges associated with the development of quantum dot solar cells. The results from this work show that the quantum dot solar cells indeed improve the efficiency via sub-bandgap photon absorption but much lower than the expected theoretical efficiencies. Yet, these devices serve as a proof of concept and the results provide vital information for future IBSC work. With further understanding of the operation of intermediate band solar cells and the identification of less expensive materials can substantially improve the solar cell efficiency and drastically cut the cell cost thereby reducing the dollar/watt cost.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- Contributing Organization:
- Rochester Inst. of Technology, NY (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
- DOE Contract Number:
- EE0005325
- OSTI ID:
- 1347995
- Report Number(s):
- DOE-UCLA-5325
- Country of Publication:
- United States
- Language:
- English
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