Nanostructuredpolythiophene hybrid chargetransfer complexes
Başlık çevirisi mevcut değil.
- Tez No: 719649
- Danışmanlar: DR. WOLFGANG MASER
- Tez Türü: Doktora
- Konular: Kimya, Kimya Mühendisliği, Chemistry, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2018
- Dil: İngilizce
- Üniversite: Universidad de Zaragoza
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 197
Özet
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Özet (Çeviri)
Conjugated polymers (CPs) exhibit unique electronic and optoelectronic properties due to their extended π orbitals along the polymer chain. They possess large absorption cross sections, reveal high fluorescence efficiencies and show remarkable charge transport characteristics. These properties render CPs as ideal candidates for synthesizing novel donoracceptor (D/A) charge transfer complexes with various nanostructures of interest for optoelectronic applications. The well-known example based on electron‐donating conjugated polymers in combination with electron accepting fullerene derivatives underlines the importance of CPs role in D/A hybrids for potential applications for thin film plastic electronics i.e. organic solar cells, organic light-emitting diodes, organic field effect transistors, chemical sensors and biosensors and flexible displays. Here, an efficient charge transfer in conjugated polymer based D/A complexes depends on the optimization of some important parameters such as i) proper adjustment of HOMO and LUMO energy levels of the D/A materials and ii) the morphology of the blend system for fine-tuning of the D/A interfaces for achieving optimal exciton dissociation and charge transport. Additionally, concerning environmental awareness, the fabrication of D/A complexes from environmentally-friendly solutions, compatible with large-area coating or printing technologies is a key requirement for their commercial implementation . In order to advance in the development of the variety of D/A hybrid structures and environmentally-friendly processing condition, this thesis focuses on the synthesis of water based nanohybrids as D/A complexes and the elucidation of the electronic interaction among the D/A units by spectroscopic techniques such as UV-visible spectroscopy, photoluminescence (steady-state and time resolved) spectroscopy, and Raman spectroscopy. On the other hand, the electrochemical and photoelectrochemical properties of hybrids were also investigated in order to gain important insights on the thin film device performance. Chapter 1 provides the general context and summarizes the general background information of (CPs), conjugated polymer nanoparticles (CPNs) and their donor-acceptor charge transfer complexes including methods of preparation and physical properties. Chapter 2 describes the synthesis and characterization of a novel water-based self-assembled nanohybrid, which consists of poly (3-hexylthiophene) nanoparticles (P3HTNPs) and graphene xx oxide (GO). P3HTNPs and P3HTNPs-GO complexes were synthesized by an in-situ reprecipitation technique. Morphological characterization reveals that the formation of P3HTNPs is successfully accomplished exhibiting particles sizes in the range of 50 to 200 nm. In the case of P3HTNPs-GO complexes the morphological studies reveal the presence of P3HTNPs in intimate contact with micrometer sized GO sheets. Importantly,, spectroscopic characterization of the samples demonstrates that GO changes the optical properties of P3HTNPs by influencing the crystalline packing of poly (3-hexylthiophene) (P3HT) chains in the forming P3HTNPs from H to H/J aggregates during the self-assembly process. Furthermore, π-π interface interactions between the P3HTNPs and GO sheets are established resulting in the creation of P3HTNPs-GO D/A charge-transfer complexes. This work demonstrates that the electronic and optoelectronic properties of conjugated polymer nanoparticles can be tuned by GO. Moreover, properties established in liquid phase are maintained in the form of films. Thus, thin film properties do not depend anymore on external processing parameters. Photoelectrochemical studies additionally underline the value P3HTNPs-GO thin films as photoactive thin layer materials with improved performance. Combined with the possibility to process these charge-transfer hybrids from water-based dispersions renders P3HTNPs-GO charge transfer complexes of special interest for the development of improved thin film optoelectronic applications. Chapter 3 focuses on photogenerated charge-transfer properties on individual nanoobjects of P3HTNPs-GO hybrids by employing Kelvin Probe Force Microscopy under dark and illuminated conditions. By mapping the local surface potential (SP) in darkness, a substructure is resolved which clearly indicates the presence of aggregate domains within the polymer nanoparticles. In addition, surface photovoltage (SPV) measurements on individual P3HTNPs nanoparticles and P3HTNPs-GO complexes were performed to shed light on the photoinduced charge generation and charge recombination mechanisms at the different nanoscale interfaces. This study is of great relevance for the improved understanding of the overall functionality thin film layers composed of individual nanoscale objects and thus for providing feedback for further optimizing the optoelectrical performance of thin film devices. Chapter 4 covers the self-assembly of novel core−shell nanoensembles consisting of 100 nm P3HTNPs as core and semiconducting CdTe quantum dots (CdTeQDs) as shell. The nanoensemble structure was accomplished by employing a re-precipitation approach. The morphology and composition of CdTeQDs/P3HTNPs nanoensembles were confirmed by highresolution scanning transmission microscopy and dynamic light-scattering studies. The xxi interaction between the outer amorphous part of the P3HTNPs core and the CdTeQDs shell is confirmed by optical characterization and photoluminescence spectra. These exhibit effective quenching of the characteristic photoluminescence of CdTeQDs at 555 nm, accompanied by simultaneous increase in the emission of P3HTNPs at 660 and 720 nm, suggesting the existence of photoinduced charge-transfer processes. Additionally, the electrochemical response on films further supports the findings of a stabilized CdTeQDs/P3HTNPs core−shell system in the solid state. Photoelectrochemical assays on CdTeQDs/P3HTNPs films show a reversible on−off photoresponse at a bias voltage of +0.8 V with a 3 times increased photocurrent compared to CdTeQDs. This study shows that the unique core−shell configuration is directly related with the donor-acceptor behavior and charge separation. Chapter 5 focuses on the preparation, characterization, and photophysical and electrochemical properties of water-dispersible polythiophene/layered transition metal dichalcogenide ensembles. The positive charges on functionalized molybdenum disulfide (MoS2) and tungsten disulfide (WS2), due to the presence of ammonium units, were exploited to electrostatically bring in contact a newly synthesized water-dispersible polythiophene derivative bearing a carboxylate moiety. This yields in water soluble polythiophene/MoS2 and water soluble polythiophene/WS2 ensembles. The electronic interactions between the materials within the nanoensembles were characterized firstly by absorption and photoluminescence titration assays. Efficient photoluminescence quenching of polythiophene emission by MoS2 and WS2 within nanoensembles, in combination with time-resolved photoluminescence assays, were observed and attributed to photoinduced electron/energy transfer from photoexcited polythiophene to MoS2 or WS2. The ensembles show enhanced photocurrent in comparison with individual exfoliated materials, especially in case of WS2. This further confirms that electron transfer between the negatively charged polymer and the positively charged transition metal dichalcogenides is taking place. All these results consistently reveal the advantageous function of electrostatic interactions between the negatively charged polymer and the positively charged transition metal dichalcogenides not only for the realization of the nanoensembles but also for succeeding efficient electronic communication. Finally, Chapter 6 provides the general conclusion of the findings and an outlook in what concerns possible opportunities and future research work
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