University of New Orleans
Ferroelectric-Semiconductor Systems for New Generation of Solar Cells.
Degree: PhD, Physics, 2017, University of New Orleans
This dissertation includes two parts. In the first part the study is focused on the fabrication of multifunctional thin films for photovoltaic applications. There is no doubt about the importance of transforming world reliance from traditional energy resources, mainly fossil fuel, into renewable energies. Photovoltaic section still owns very small portion of the production, despite its fast growth and vast research investments. New methods and concepts are proposed in order to improve the efficiency of traditional solar cells or introduce new platforms. Recently, ferroelectric photovoltaics have gained interest among researchers. First objective in application of ferroelectric material is to utilize its large electric field as a replacement for or improvement of built-in electric field in semiconductor p-n junctions which is responsible for the separation of generated electron-hole pairs. Increase in built in electric field will increase open-circuit voltage of the solar cell.
In this regard, thin films of ferroelectric hafnium dioxide doped with silicon have been fabricated using physical vapor deposition techniques. Scanning probe microscopy techniques (PFM and KPFM) have been employed to analyze ferroelectric response and surface potential of the sample. The effects of poling direction of the ferroelectric film on the surface potential and current-voltage characteristics of the cell have been investigated. The results showed that the direction of poling affects photoresponse of the cell and based on the direction it can either improved or diminished.
In the second part of this work, epitaxial thin films have been synthesized with physical vapor deposition techniques such as sputtering and electron beam evaporation for the ultimate goal of producing multifunctional three-dimensional structures. Three-dimensional structures have been used for applications such as magnetic sensors, filters, micro-robots and can be used for modification of the surface of solar cells in order to improve light absorption and efficiency. One of the important techniques for producing 3-D structures is using origami techniques. The effectiveness of this technique depends on the control of parameters which define direction of bending and rolling of the film or curvature of the structure based on the residual stress in the structure after film’s release and on the quality and uniformity of the film. In epitaxially grown films, the magnitude and direction of the stress are optimized, so the control over direction of rolling or bending of the film can be controlled more accurately. For this purpose, deposition conditions for epitaxy of Zn, Fe, Ru, Ti, NaCl and Cr on Si, Al2
or MgO substrates have been investigated and optimized. Crystallinity, composition and morphology of the films were characterized using reflective high energy diffraction (RHEED), Auger electron spectroscopy (AES), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM).
Advisors/Committee Members: Prof. Leszek Malkinski.
Subjects/Keywords: photovoltaic, ferroelectric, hafnium dioxide, polarization, micro-origami, epitaxy; Semiconductor and Optical Materials
to Zotero / EndNote / Reference
APA (6th Edition):
Eskandari, R. (2017). Ferroelectric-Semiconductor Systems for New Generation of Solar Cells. (Doctoral Dissertation). University of New Orleans. Retrieved from http://scholarworks.uno.edu/td/2318
Chicago Manual of Style (16th Edition):
Eskandari, Rahmatollah. “Ferroelectric-Semiconductor Systems for New Generation of Solar Cells.” 2017. Doctoral Dissertation, University of New Orleans. Accessed June 25, 2017.
MLA Handbook (7th Edition):
Eskandari, Rahmatollah. “Ferroelectric-Semiconductor Systems for New Generation of Solar Cells.” 2017. Web. 25 Jun 2017.
Eskandari R. Ferroelectric-Semiconductor Systems for New Generation of Solar Cells. [Internet] [Doctoral dissertation]. University of New Orleans; 2017. [cited 2017 Jun 25].
Available from: http://scholarworks.uno.edu/td/2318.
Council of Science Editors:
Eskandari R. Ferroelectric-Semiconductor Systems for New Generation of Solar Cells. [Doctoral Dissertation]. University of New Orleans; 2017. Available from: http://scholarworks.uno.edu/td/2318