Date of Graduation

5-2013

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Manasreh, Omar O.

Committee Member

Yu, Shui-Qing "Fisher"

Second Committee Member

Ang, Simon S.

Keywords

Applied sciences; Intermediate band solar cells; Semiconductor quantum structures; Semiconductor solar cells

Abstract

Intermediate band solar cells based on quantum dots and quantum wells with anti-reflection coating are investigated in this thesis. The demand for high efficient solar cells as an alternate source of energy is the main motivation for this research project. Intermediate band solar cells based on quantum dots were the subject of intensive research in recent years. High power conversion efficiency was predicted from InAs/GaAs intermediate band solar cells as the presence of InAs quantum dots increased the absorption below the band gap of the host material.

In this thesis, an attempt has been made to further increase the absorption of GaAs solar cells by embedding InAs quantum dots in InxGa1-xAs quantum wells. The quantum efficiency and spectral response measurements of quantum dots embedded in quantum well devices exhibit an extended response till 1280 nm in the near infrared region of the electromagnetic spectrum. The interband transition peaks associated with the InxGa1-xAs quantum well exhibit a red shift as In mole fraction (x) in InxGa1-xAs quantum well is increased above 0%. The short circuit current density increased, while open circuit voltage decreased, as x is increased.

In addition, the use of inexpensive anti-reflection coating (ARC) on these intermediate band solar cells has been studied. Anti-reflection coating based on Zinc oxide (ZnO) has significantly improved the power conversion efficiency of the solar cells. The ZnO synthesized using sol-gel technique was spin coated on the solar cells and subsequently annealed. The short circuit current density was significantly increased after the deposition of the ARC. Enhancement of the order of 42 % in the power conversion efficiency was obtained. Around 43% enhancement in quantum efficiency and 44% enhancement in spectral response measurements were also observed.

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