Rationalizing the Band Gap Tunability of Semiconductors via Electronic Structure Calculations

Author

Matthew N. Srnec, Duquesne UniversityFollow

Defense Date

6-29-2017

Graduation Date

Summer 1-1-2017

Availability

One-year Embargo

Submission Type

dissertation

Degree Name

PhD

Department

Chemistry and Biochemistry

Committee Chair

Jeffrey D. Evanseck

Committee Member

Jennifer A. Aitken

Committee Member

M. Rita Mihailescu

Committee Member

Ralph A. Wheeler

Keywords

electronic structure, semiconductors, titanium dioxide, density functional theory, photovoltaic solar cells

Abstract

The polymorphs of titanium dioxide and various diamond-like semiconductor materials are promising candidates in photovoltaic solar cell applications. Several of these polymorphs have been studied with experimental and computational methods, which often aim at tuning the electronic structure, particularly the band gap value of the crystalline solid. Prior studies report that the addition of a substituent into the structure of titanium dioxide decreases its band gap value, but the reasons for this are unknown. Possible explanations for the change in band gap involve the substituent atom's crystal radius, electronegativity, and ionization energy. Understanding the cause of these changes will provide great insight in designing new materials. The hypothesis of this work is that a substituent atom's crystal radius has a greater impact on the change in band gap of titanium dioxide than the substituent atom's electronegativity. In an aim to test this hypothesis, atoms of differing chemical properties were selected for substitution into the rutile and anatase polymorphs of titanium dioxide. The electronic structure (band structure and density of states) of the substituted systems was calculated using the full-potential linearized-augmented plane wave approach of density functional theory in the WIEN2k software. Upon calculating the electronic structure, the relationships between the band gap value and various chemical properties were evaluated.

Language

English

Recommended Citation

Srnec, M. N. (2017). Rationalizing the Band Gap Tunability of Semiconductors via Electronic Structure Calculations (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/245

Additional Citations

Srnec, M. et al. Teaching reciprocal space to undergraduates via theory and code components of an IPython notebook. J. Chem. Educ. 2016, 93, 2106-2109.

Srnec, M. et al. A python program for solving Schrodinger's equation in undergraduate physical chemistry. J. Chem. Educ. 2017, 94, 813-815.

Rosmus, K. et al. Synchrotron X-ray powder diffraction and electronic band structure of alpha- and beta-Cu₂ZnSiS₄. Z. Anorg. Allg. Chem. 2012, 638, 2578-2584.

Rosmus, K. et al. Optical nonlinearity in Cu₂CdSnS₄ and alpha/beta-Cu₂ZnSiS₄: diamond-like semiconductors with high laser-damage thresholds. Inorg. Chem. 2014, 53, 7809-7811.

Devlin, K. et al. Polymorphism and second harmonic generation in a novel diamond-like semiconductor: Li₂MnSnS₄. J. Solid State Chem. 2015, 231, 256-266.

Srnec, M.N.; Madura, J.D. "RE: Revisiting the thermodynamic model from Goldstein et al. (1992)" (2016); http://science.sciencemag.org/content/256/5062/1425.e-letters.