Degree Type

Dissertation

Date of Award

2011

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

First Advisor

Zhiqun Lin

Abstract

Conjugated polymer-nanocrystals nanohybrids, capitalizing on the advantages peculiar to solution-processable conjugated polymers (CPs) in conjunction with the high electron mobility and tunable optical properties of inorganic nanocrystals (NCs), have attracted considerable attention to achieve high efficiency organic photovoltaics at low cost. The most elegant approach to obtain CP-NC nanohybrids is to chemically tether CPs on the NC surface. In our study, semiconductor organicinorganic nanocomposites were synthesized by directly grafting CP, poly(3-hexylthiophene), onto cadmium selenide nanorod surface (i.e., preparing P3HTCdSe NR nanocomposites). The direct grafting was accomplished by two coupling reactions: Heck coupling of vinyl-terminated P3HT with bromobenzylphosphonic acid functionalized CdSe NRs (i.e., BBPA-CdSe), and a newly developed catalyst-free click reaction of ethynyl-terminated P3HT with azide functionalized CdSe NRs. Such rationally designed nanocomposites possessed a well-defined interface between P3HT and CdSe NRs, thereby promoting the effective dispersion of CdSe NRs within the nanocomposites and facilitating their electronic interaction. This is the first study of directly placing conjugated copolymers in intimate contact with semiconductor NRs, dispensing with the need for ligand exchange chemistry as in copious past work. These nanocomposites offer a maximum interfacial area between the constituents for efficient exciton dissociation. As such, it represents a significant advance in rational design and fabrication of organicinorganic hybrid solar cells with improved power conversion efficiency.

As one of the most typical film preparation methods, the Langumuir-Blodgett (LB) technology has been widely utilized to produce copolymer films with mono- or multi- molecule layers for potential applications in microlithography, devices, and biomimetic thin films. In our study, self-assembly of a series of newly synthesized functional block copolymers (e.g., conjugated, bio-degradable, responsive, etc.) with various novel structures (linear, brush, comb, and star-like) were systematically explored using the LB technique. The influence of the chemical composition and molecular architectures on the self-assembly process was carefully investigated. Various models were proposed to elucidate the complex dynamic self-assembly process. This study not only complements the well-known models of self-assembly of amphiphilic block copolymers at the air/water interface, but also provides a general means of fabricating LB monolayer into controllable structures and integrating the intriguing functionalities in a desirable manner.

DOI

https://doi.org/10.31274/etd-180810-488

Copyright Owner

Lei Zhao

Language

en

Date Available

2012-04-28

File Format

application/pdf

File Size

205 pages

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