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Full-Text Articles in Engineering

Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang Nov 2016

Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang

Doctoral Dissertations

Polymer-based semiconducting materials are promising candidates for large-scale, low-cost photovoltaic devices. To date, the efficiency of these devices has been low in part because of the challenge of optimizing molecular packing while also obtaining a bicontinuous structure with a characteristic length comparable to the exciton diffusion length of 10 to 20 nm. In this dissertation we developed an innovative evaporation-induced nanoparticle self-assembly technique, which could be an effective approach to fabricate uniform, densely packed, smooth thin films with cm-scale area from home-made P3HT nanoparticles. Unlike the previous reports of nanoparticle-based film formation, we use a mixture of two solvents so …


Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang Mar 2016

Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang

Doctoral Dissertations

This thesis describes the solution behavior and interfacial properties of electronically active polymers. The performance of such polymers in devices is often determined by their chain conformation and morphology in solution and in thin films. For example, the intricate balance between polymer domain size and crystalline packing of electron donor and acceptor components, as well as the properties at the polymer-metal interface, are crucial for achieving optimal performance in devices, such as solar cells. Chapter 1 presents the current progress in polymer-based solar cells, their fundamental principles, and key factors to improve their efficiency. Literature precedents on the development of …


Refractive Index Engineering And Optical Properties Enhancement By Polymer Nanocomposites, Cheng Li Mar 2016

Refractive Index Engineering And Optical Properties Enhancement By Polymer Nanocomposites, Cheng Li

Doctoral Dissertations

The major part of this dissertation discusses the engineering of the refractive index of materials using solution-processable polymer nanocomposites and their applications in building optical components and devices. Three particular polymer nanocomposites have been introduced to achieve materials with tunable refractive indices and enhanced optical properties, which can be used to manipulate the behavior of light or electromagnetic radiations. In the first system, polyhedral oligomeric silsesquioxane (POSS)/polymer nanocomposites are developed. Thin films with tunable, low refractive indicies were fabricated from the composites. The mechanical strength of these films was characterized, and their application in antireflective coatings is discussed. In the …


(I) Polymer Nanocomposites: Rheology And Processing For Mesoporous Materials And (Ii) Nanopatterning Of Metal Oxides Using Soft Lithography, Rohit Kothari Mar 2016

(I) Polymer Nanocomposites: Rheology And Processing For Mesoporous Materials And (Ii) Nanopatterning Of Metal Oxides Using Soft Lithography, Rohit Kothari

Doctoral Dissertations

The research in this dissertation is categorized into two parts. The first part is focused on investigation of order-to-disorder transitions (ODT) in nanocomposites of an amphiphilic block copolymer containing various hydrogen-bonded additives, and fabrication of novel mesoporous silica based materials by utilizing such nanocomposites as templates. Disordered Pluronic®, poly(ethylene oxide) (PEO)−poly(propylene oxide) (PPO)−PEO triblock copolymer upon blending with small molecule additives containing hydrogen-bond-donating functional groups (carboxyl or hydroxyl) result into ordered nanoscale morphologies by preferentially interacting with the hydrophilic PEO chains in the Pluronic®. The dependence of ODT-temperature in these novel Pluronic®/small-molecule-additive complexes on composition, number and type of functional …


Theoretical Studies Of Atomic Transport In Ternary Semiconductor Quantum Dots And Charge Transport In Organic Photovoltaic Active Layers, Xu Han Mar 2016

Theoretical Studies Of Atomic Transport In Ternary Semiconductor Quantum Dots And Charge Transport In Organic Photovoltaic Active Layers, Xu Han

Doctoral Dissertations

Ternary semiconductor quantum dots with thermodynamically stable structures are particularly important for achieving optimal performance in optoelectronic and photovoltaic applications. Ternary quantum dots (TQDs) are typically synthesized in the form of core/shell structures. However, misfit strain induced by the abrupt core/shell interface can change the nature of the TQDs dramatically, leading to unstable optoelectronic function. In this thesis, a transient species transport model is developed to predict species distributions in TQDs during their thermal annealing. Specifically, the interdiffusion kinetics is analyzed of group-VI species in ZnSe1-xSx and ZnSe1-xTex TQDs and of group-III species in …


Model Systems For Characterizing The Intrinsic Properties Of Polymer Semiconductors: Oligomers And Single Crystals, Nicholas S. Colella Mar 2016

Model Systems For Characterizing The Intrinsic Properties Of Polymer Semiconductors: Oligomers And Single Crystals, Nicholas S. Colella

Doctoral Dissertations

Polymer semiconductors hold great promise for the realization of inexpensive, flexible electronic devices. One of the greatest strengths of these materials, their low-cost processability from solution, results in a wide range of solid-state structures. The crystallinity and morphology of these materials strongly impacts their performance as charge carriers. Furthermore, the nature of polymerization inherently leads to the production of materials which are disperse in their molecular character, with regard to both coupling and molecular weight. Thus, it is difficult to deconvolute the intrinsic properties of polymer semiconductors from their synthetic and processing conditions. Polythiophenes are particularly susceptible to performance variations …