The role of the oxide/organic and organic/organic interfaces in small-molecule planar-Heterojunction (PHJ) photovoltaics was investigated with three interrelated projects: i) indium-tin oxide (ITO) bottom contact electrodes were modified with gold nanoparticles (Au-NPs) to improve rates of charge-transfer at the donor/oxide interface, ii) donor layers in OPVs were textured to increase charge generation at the organic/organic' interface, and iii) the effect of co-facial overlap on device performance via tuning of the electron acceptor orientation at the organic/organic interface. The modification of ITO with Au-NPs showed increased performance in small-molecule OPVs when compared to non-processed ITO devices due to the interactions between the Au-NPs and the donor material. Textured TiOPc increased overall device performance by a factor of 2X via the increased surface area, near-IR absorption, and increased mobilities. Modified and un-modified PTCDA acceptors showed that co-facial overlap at the organic/organic' interface is a large determinant in device performance, while the performance in small-molecule planar-heterojunction photovoltaics were severely affected by the pre-treatment process, most likely due to the particular interactions between the oxide and the donor material.

No description available.

No description available.

The design of organic electronic devices is heavily dependent upon the orientation of the molecular solid which influences the direction that charge carriers are able to traverse across the π-system. In this work, thin films of copper phthalocyanine (CuPc) were deposited using thermal deposition over SiO2 and CuI both substrates having demonstrated the ability to confer different orientations onto thermally evaporated CuPc. A variety of scattering and spectroscopic techniques were utilized to characterize the electronic, chemical, and crystalline structures of CuPc to determine the effects that the substrates have over these structures when the molecule's self-assembly is altered. The findings in this study will be integrated into future works as reference points and control studies in order to draw meaningful and direct connections between MPcs that have differing electron affinity, transition metal cores, and functional groups as well as multi-layers of various MPcs within unique heterojunctions.

Germanium(ll)phthalocyanine forms crystals belonging to space group P2/c with a=27.11, sigma=0.012 Å, b=10.39, sigma=0.020 Å, c=21.96, sigma=0.014 Å, beta=107.86, sigma-0.0680. There are eight molecules per unit cell.Patterson maps show that the molecule is planar, that the molecular axis is inclined 500 to the b axis, and that molecules are located parallel to each other along the b axis with an interplanar distance of 3.9 Å.

The work in this dissertation describes improved methods of asymmetrically substituted Pc derivative synthesis addressing some currently encountered problems including: (1) the need for facile synthesis of asymmetric Pc/Nc hybrids; (2) a lack of general methods for producing asymmetric Pc materials with structural diversity. Chapter 1 provides a concise review on Pc and Pc/perylenediimide (PDI) derivatives that have been reported as a part of architecture in monochromophoric or multichromophoric molecules for energy and charge transfer studies. In addition, the intrinsic electronic and photophysical properties suitable for OPV applications, such as charge transfer rate, lifetime of charge separated state, and transfer pathway are also discussed. Chapter 2 details the use of ROMP-Capture-Release to synthesize a small library of asymmetric Pc/Nc hybrids and study of chemical and physical properties of these structurally related asymmetric chromophores and the corresponding symmetric Pc and Nc in both metalated (Zn) and unmetallated form. The extension of the Pc aromatic core as well as the asymmetry afforded by the unique quadrant can result in modulated physical properties, particularly bathochromic shifted electronic absorption spectra. Further modification of the pendent hydroxyl group on the molecule demonstrated the possibility for covalently grafting Pcs onto inorganic contacts such as ITO and TiO₂. Chapter 3 reports the investigation of using an asymmetric Pc as the platform for the preparation of a small library of zinc hexatriazolyl-monohydroxyphthalocyanines via Cu-catalyzed azide-alkyne cycloaddition (CuAAC). The modification of peripheral substituents was demonstrated using azides bearing hydrophobic, photo-crosslinkable, and electroactive moieties. Monitoring the click chemistry by both UV-Vis and FT-IR spectroscopies was performed to provide insight into the role of azide equivalent, reaction time, and catalyst on reaction progress. Chapter 4 describes the synthesis and characterization of a novel series of Pc-PDI dyads with different perylene bay-functional groups (H, thioether, and sulfonyl), as well as phosphonic acid as an anchoring group connected to the perylene moieties, for the studies of molecular-level heterojunction on transparent conductive oxides. The developed model system for further electrochemical analysis was proved to firmly attach to the ITO surface by ATR-UV/Vis spectroscopy.

No description available.

This thesis describes the fabrication and properties of novel organic/silicon hybrid field-effect transistor gas sensors. Whilst most of the work used the emeraldine base form of the conductive polymer polyaniline, the response of a device incorporating a metal-free phthalocyanine is also reported. Arrays of p-type transistors in which the gate electrodes were replaced by 'charge-flow' capacitors were fabricated using standard semiconductor processing techniques. Each array consisted of four devices in which the width of metallisation removed from the gate electrode (total width 72 µm) varied from 0 µm (i.e. the control device) to 35 µm. Thin films of the gas-sensitive organic materials were deposited by spin-coating, and chemically patterned within the holes in the gate metallisation. A delay, referred to as the 'turn-on' response, was observed in the drain current on application of a gate voltage. This was shown to depend on the temperature, level of humidity and the presence of certain gases. The electrical operating characteristics of the hybrid device with and without the polyaniline were examined. These included capacitance-voltage measurements, the 'turn-on' response at different temperatures and the variation of threshold voltage with temperature. From these results an understanding of the effect of integrating polyaniline within a p-channel transistor structure was obtained. The 35 µm gate-hole sensor incorporating polyaniline was found to be sensitive to NO(_x) and SO(_2) at room temperature at concentrations as low as 1 or 2 ppm. Decreasing the gate-hole area, and therefore the surface area of polyaniline, reduced the sensitivity of the device. The reactions were found to be reversible, although complete recovery required approximately eight hours. A similar sensor incorporating a metal-free phthalocyanine compound was reversibly sensitive to 2 ppm NO(_x) with a more rapid recovery of five hours. There was no observable response to SO(_2) or H(_2)S up to 30 ppm.

Organic photovoltaic (OPV) devices utilizing organic (carbon-based) semiconductors have maintained research interest due to their potential for inexpensive, non-toxic, flexible, and lightweight solar modules. Numerous organic polymers and small molecules have been investigated for OPV applications, however a focus on maximizing the power conversion efficiency (PCE) of lab-scale devices has generated many novel active materials that are too complex to be realistically synthesized on a commercial scale. It has become apparent that developing low-cost, scalable, and stable active materials is crucial for the commercialization of OPV devices. Metal phthalocyanines (MPcs) are a well-known family of molecules with established scale up chemistry from their use as colorants and have demonstrated strong performance as low-cost semiconductors in organic electronic devices. However, their potential in solution-processed OPV devices has not been fully realized. In this thesis, a series of materials based on silicon phthalocyanine (SiPc) and tin phthalocyanine (SnPc) were synthesized and characterized. Novel molecular designs and OPV device architectures were investigated to further establish the use MPcs as low-cost active materials and to probe new applications. Specifically, the chemical and physical differences of structurally analogous soluble SiPc and SnPc derivatives were examined for the first time. The ability of a SiPc derivative to act as a thermal crosslinker to stabilize active layer morphology while simultaneously contributing to photocurrent generation was also proven. SiPc derivatives were then studied as electron acceptors paired with P3HT and PBDB-T donor polymers, achieving a PCE up to 4.3 %. The results herein establish new potential roles for group 14 MPcs in OPV devices while also demonstrating their synthetic simplicity and versatility. This work also serves as a basis for the wealth of chemical functionalization which remains available for continued optimization of these materials.

This thesis investigates the electronic structure of iron phthalocyanine (Fe(II)Pc) andiron phthalocyanine chloride (Fe(III)PcCl) immobilized on surfaces. For this purposetwo different deposition methods are used and compared: smearing the molecularpowder under atmosphere condition and evaporation of a molecular layer inultra-high vacuum. The electronic states of FePc and FePcCl are probed withphotoelectron spectroscopy (PES) and compared in relation to the ionic state of thecentral metal (Fe). The PE spectra show that evaporation of FePcCl at around 350°Cresults in dissociation of the chlorine from the FePc molecule, which is stable at thistemperature. Mass spectroscopic measurements during heating of FePcCl in ultra-highvacuum (UHV) show a clear Cl signal for temperature still below 250°C. Theoreticalcalculations of the binding energy for Cl in FePcCl seem to indicate dissociation of theCl from the molecules.