CdTe has recently become the most commercially successful polycrystalline thin film solar module material. Its low cost, large-area solar module is reshaping the silicondominated solar panel market; however, CdTe has much room to improve and thus more fundamental understanding is needed. Current thin film solar cell research is focused on two areas: One is identifying loss mechanisms and understanding the polycrystalline nature of single junction device to improve device performance. Another is searching for new materials and fabricating tandem solar cells. In this study, along with other people’s work to improve the efficiency of CdTe solar module, I studied loss mechanism and growth mode of CdTe solar cells to have fundamental understanding of polycrystalline films. In addition to that, in an effort to make tandem solar cells, I fabricated and characterized CdSe solar cells, which is considered as an ideal candidate for the top cell with its band gap of 1.7 eV.
This dissertation is designed to show similarities and differences between CdTe and CdSe solar cells, side by side. After the introduction (Chapter1), I will review the physical properties of CdTe and CdSe solar cells (Chapter 2). Two primary tools to study defects and surface morphology were photoluminescence (PL) and atomic force microscopy (AFM). PL showed information on the crystallinity and defects of CdTe and CdSe films before and after annealing.(Chapter 3). AFM measurements and their analysis using scaling theory revealed information on the growth modes of CdTe and CdSe films.(Chapter 4).
With the goal of exploring suitability for tandem structures with ~1.7 eV top cell and ~1.1 eV bottom cell, I fabricated and characterized single-junction CdSe devices. (Chapter 5) In addition, for the bottom cell I fabricated HgCdTe cells with Eg~1.1 eV. Single junction HgCdTe and two-terminal CdTe/HgCdTe tandem solar cells were fabricated and characterized. (Chapter 5)
|Commitee:||Amar, Jacques, Compaan, Alvin, Giolando, Dean, Karpov, Victor, Kvale, Thomas|
|School:||The University of Toledo|
|School Location:||United States -- Ohio|
|Source:||DAI-B 78/11(E), Dissertation Abstracts International|
|Keywords:||AFM, CdSe, CdTe, Photovoltaic, Scaling, Solar cell|
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