Analysis Of The External Quantum Efficiency Of Quantum Dot Enhanced Multijunction Solar Cells

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Analysis of the External Quantum Efficiency of Quantum Dot-enhanced Multijunction Solar Cells

This thesis focuses on the analysis of the external quantum efficiency of quantum dot-enhanced multi-junction solar cells. Divided in four major parts, it uses the experimental methodology developed in the SUNLAB. At first, a model is introduced to calculate the external quantum efficiency of single and multi-junction solar cells. This model takes into account the semiconductor physics governing the electrical property of the solar cell. It furthermore takes into account the optical transmission and reflection in the semiconductor structure using a transfer matrix method. The calculated curve fits a single junction GaAs solar cell's external quantum efficiency to a high degree of precision. Finally, an InGaP/GaAs/Ge solar cell's external quantum efficiency is calculated and it reproduces accurately the behavior of a measured cell. Second, the reflectivity of a solar cell is studied. An analysis technique involving using the fast Fourier transform of the oscillation in the reflectivity is introduced. This technique extracts the thicknesses of the top and middle subcells. The reflectivity is subsequently calculated using the transfer matrix method and it reproduces the behavior of the measured samples. Third, the effect of the addition of quantum dots in the middle subcell is studied. It is demonstrated that they extend the absorption range of the middle subcell. This is completed by first modeling the quantum mechanical behavior of the electrons and holes in the nanostructure. Their emission and absorption properties are derived. Those derived properties are verified by experimentally measured photoluminescence and electroluminescence of the nanostructures. The resulting model is then compared to experimentally measured external quantum efficiencies of single junction and multi-junction quantum dot-enhanced solar cells. Finally, a study of the bottom subcell artifact is completed. Using the fill-factor bias experiment, each of the contribution of the light coupling and the internal voltage biasing is decoupled. For the measured sample, an optimal voltage of 2.1 V is found to minimize the artifact. At this point, the internal voltage biasing creates an artifact of 1 % and the light coupling artifact is 8 %.
Nanostructured Solar Cells

This book is a printed edition of the Special Issue "Nanostructured Solar Cells" that was published in Nanomaterials
Quantum Dots

Author: Ameenah Al-Ahmadi
language: en
Publisher: BoD – Books on Demand
Release Date: 2012-04-04
The book “Quantum dots: A variety of a new applications” provides some collections of practical applications of quantum dots. This book is divided into four sections. In section 1 a review of the thermo-optical characterization of CdSe/ZnS core-shell nanocrystal solutions was performed. The Thermal Lens (TL) technique was used, and the thermal self-phase Modulation (TSPM) technique was adopted as the simplest alternative method. Section 2 includes five chapters where novel optical and lasing application are discussed. In section 3 four examples of quantum dot system for different applications in electronics are given. Section 4 provides three examples of using quantum dot system for biological applications. This is a collaborative book sharing and providing fundamental research such as the one conducted in Physics, Chemistry, Biology, Material Science, Medicine with a base text that could serve as a reference in research by presenting up-to-date research work on the field of quantum dot systems.