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Full-Text Articles in Nanoscience and Nanotechnology

Exceeding Conventional Photovoltaic Efficiency Limits Using Colloidal Quantum Dots, Gregory F. Pach Apr 2017

Exceeding Conventional Photovoltaic Efficiency Limits Using Colloidal Quantum Dots, Gregory F. Pach

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

Colloidal quantum dots (QDs) are a widely investigated field of research due to their highly tunable nature in which the optical and electronic properties of the nanocrystal can be manipulated by merely changing the nanocrystal’s size. Specifically, colloidal quantum dot solar cells (QDSCs) have become a promising candidate for future generation photovoltaic technology. Quantum dots exhibit multiple exciton generation (MEG) in which multiple electron-hole pairs are generated from a single high-energy photon. This process is not observed in bulk-like semiconductors and allows for QDSCs to achieve theoretical efficiency limits above the standard single-junction Shockley-Queisser limit. However, the fast expanding ...


Flexible, Photopatterned, Colloidal Cdse Semiconductor Nanocrystal Integrated Circuits, Franklin Scott Stinner Jan 2017

Flexible, Photopatterned, Colloidal Cdse Semiconductor Nanocrystal Integrated Circuits, Franklin Scott Stinner

Publicly Accessible Penn Dissertations

As semiconductor manufacturing pushes towards smaller and faster transistors, a parallel goal exists to create transistors which are not nearly as small. These transistors are not intended to match the performance of traditional crystalline semiconductors; they are designed to be significantly lower in cost and manufactured using methods that can make them physically flexible for applications where form is more important than speed. One of the developing technologies for this application is semiconductor nanocrystals.

We first explore methods to develop CdSe nanocrystal semiconducting “inks” into large-scale, high-speed integrated circuits. We demonstrate photopatterned transistors with mobilities of 10 cm2/Vs on ...


Exceeding Conventional Photovoltaic Efficiency Limits Using Colloidal Quantum Dots, Gregory F. Pach Jan 2017

Exceeding Conventional Photovoltaic Efficiency Limits Using Colloidal Quantum Dots, Gregory F. Pach

Electrical Engineering Graduate Theses & Dissertations

Colloidal quantum dots (QDs) are a widely investigated field of research due to their highly tunable nature in which the optical and electronic properties of the nanocrystal can be manipulated by merely changing the nanocrystal’s size. Specifically, colloidal quantum dot solar cells (QDSCs) have become a promising candidate for future generation photovoltaic technology. Quantum dots exhibit multiple exciton generation (MEG) in which multiple electron-hole pairs are generated from a single high-energy photon. This process is not observed in bulk-like semiconductors and allows for QDSCs to achieve theoretical efficiency limits above the standard single-junction Shockley-Queisser limit. However, the fast expanding ...


Controlling The Photophysical Properties Of Semiconductor Quantum Dot Arrays By Strategic Alteration Of Their Surface Chemistry, Ashley R. Marshall Jan 2017

Controlling The Photophysical Properties Of Semiconductor Quantum Dot Arrays By Strategic Alteration Of Their Surface Chemistry, Ashley R. Marshall

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Semiconductor quantum dots (QDs) are interesting materials that, after less than 40 years of research, are used in commercial products. QDs are now found in displays, such as Samsung televisions and the Kindle Fire, and have applications in lighting, bio-imaging, quantum computing, and photovoltaics. They offer a large range of desirable properties: a controllable band gap, solution processability, controlled energy levels, and are currently the best materials for multiple exciton generation. The tunable optoelectronic properties of QDs can be controlled using size, shape, composition, and surface treatments—as shown here. Due to the quasi-spherical shape of QDs the surface to ...


Synthesis And Modification Of Ternary And Quaternary Chalcogenide Nanocrystals, Michelle J. Thompson Jan 2016

Synthesis And Modification Of Ternary And Quaternary Chalcogenide Nanocrystals, Michelle J. Thompson

Graduate Theses and Dissertations

ABSTRACT

Cu2ZnSnS4 (CZTS) is a promising quaternary material for solar energy conversion and catalysis, but until recently, synthesis of phase pure, anisotropic CZTS nanocrystals remained a challenge. In this thesis, we demonstrate control over the morphology and composition of CZTS nanorods, controlled doping of CZTS nanorods with several transition metal cations, and we extend the synthetic method to ternary sulfide nanocrystals.

We begin by showing that the initial concentration of cationic precursors has a dramatic effect on the morphology and composition of hexagonal wurtzite CZTS nanorods. Our experiments strongly indicate that Cu(C5H7O2)2 is the most reactive of the ...


Developent Of A Phospholipid Encapsulation Process For Quantum Dots To Be Used In Biologic Applications, Logan Grimes Jun 2014

Developent Of A Phospholipid Encapsulation Process For Quantum Dots To Be Used In Biologic Applications, Logan Grimes

Master's Theses and Project Reports

The American Cancer Society predicts that 1,665,540 people will be diagnosed with cancer, and 585,720 people will die from cancer in 2014. One of the most common types of cancer in the United States is skin cancer. Melanoma alone is predicted to account for 10,000 of the cancer related deaths in 2014. As a highly mobile and aggressive form of cancer, melanoma is difficult to fight once it has metastasized through the body. Early detection in such varieties of cancer is critical in improving survival rates in afflicted patients. Present methods of detection rely on visual ...


Shape-Control And Doping Of Lanthanides And Transition Metal Oxide Nanocrystals With Tailored Properties And Their Shape-Directed Self-Assembly, Taejong Paik Jan 2014

Shape-Control And Doping Of Lanthanides And Transition Metal Oxide Nanocrystals With Tailored Properties And Their Shape-Directed Self-Assembly, Taejong Paik

Publicly Accessible Penn Dissertations

Lanthanide and transition metal oxides are widely used in various applications such phosphors, lasers, magnets, and catalysts, and have formed an important platform for biomedical research and clinical medicine. The synthesis of highly uniform nanomaterials with controlled size, shape, and compositions is paramount to precisely understanding their physical properties and to arrange them into highly ordered arrays to design functional metamaterials. Herein, I describe novel chemistry to synthesize highly uniform lanthanide and transition metal oxide nanocrystals. The size, shape, and compositions of lanthanide-based nanocrystals are systematically controlled with the addition of alkali metal salts. The reaction mechanism is investigated to ...


Synthesis And Characterization Of Transition Metal Arsenide Nanocrystals And The Metastability And Magneto-Structural Phase Transition Behavior Of Mnas Nanocrystals, Yanhua Zhang Jan 2013

Synthesis And Characterization Of Transition Metal Arsenide Nanocrystals And The Metastability And Magneto-Structural Phase Transition Behavior Of Mnas Nanocrystals, Yanhua Zhang

Wayne State University Dissertations

This dissertation study focuses on (1) probing the magneto-structural phase transformation in nanoscale MnAs; (2) evaluation of the size-dependent phase stability of type-B MnAs (prepared by rapid injection); and (3) developing a general synthetic method for transition metal arsenide nanoparticles.

Discrete MnAs nanoparticles that adopt different structures at room temperature (type-A, α-structure and type-B, β-structure) have been prepared by the solution-phase arrested precipitation method. Atomic pair distribution and Rietveld refinement were employed on synchrotron data to explore the structural transitions of the bulk and nanoparticle samples, and these results were compared to AC magnetic susceptibility measurements of the samples. The ...


Semiconductor Nanocrystal Building Blocks For Solar Applications: Synthesis, Self-Assembly, And Film Characterization, Danielle Christina Reifsnyder Jan 2013

Semiconductor Nanocrystal Building Blocks For Solar Applications: Synthesis, Self-Assembly, And Film Characterization, Danielle Christina Reifsnyder

Publicly Accessible Penn Dissertations

Semiconductor nanocrystals have emerged as promising materials for light harvesting and production of electrical energy. Their unique optical properties and solution processibility suggest that they can be utilized in new ways to build on the knowledge base existing from the study of bulk semiconductors. Here, CuInSe2, CdTe, and CdSe are discussed. Synthetic control of size, shape, crystal structure, and elemental composition are crucial to realizing the potential of these nanoscale building blocks. In this work, new methods for colloidal synthesis of semiconducting nanocrystals are presented. As a consequence, the improved control over structure makes it possible to self-assemble them into ...


Ultrafast Optical Studies Of Multiple Exciton Generation In Lead Chalcogenide Quantum Dots, Aaron G. Midgett Jan 2011

Ultrafast Optical Studies Of Multiple Exciton Generation In Lead Chalcogenide Quantum Dots, Aaron G. Midgett

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Providing affordable, clean energy is one of the major challenges facing society today, and one of the promising solutions is third generation solar energy conversion. Present day, first and second-generation solar cells can at most convert each absorbed photon into a single electron hole pair, thereby establishing a theoretical limit to the power conversion efficiency. The process of multiple exciton generation (MEG) in semiconductor quantum dots increases that theoretical efficiency from 33% to 42% by utilizing the excess energy of high energy photons that is otherwise wasted as heat to excite a second electron-hole pair, thereby boosting the potential photocurrent ...