Browsing by Subject "rubrene"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    A Systematic Study of Acene Derivatives: Synthesis, Crystal Structures, Optical and Electrochemical Characterizations
    (2018-08) Zhang, Zhuoran
    This Thesis describes a systematic study towards a series of polycyclic aromatic hydrocarbons (PAHs). The objectives are to develop convenient and efficient synthetic approaches to unique aromatic frameworks in order to probe their optical and electronic properties. The ultimate goal for these studies is to establish structure−property relationships in organic electronic materials. Chapter 1 of this Thesis briefly reviewed the history and current challenge in organic electronic materials. In Chapter 2, the study of a benchmark p-type organic semiconductive material – rubrene is described. Fluorination, a strategy often used to tune the crystallographic and opto-electronic properties, is involved. Synthetic routes to partially and fully fluorinated rubrene derivatives are developed. The effect of fluorination is examined by optical and electrochemical measurements, and more importantly, by the influence on the crystal packing motifs. Fluorine-based intermolecular interactions are found to play an important role in the assembly of rubrene crystals. Chapter 3 elaborates on the work in developing a new type of PAH – dibenzo[g,s]rubicene, the structure of which contains five-membered rings that are embedded in a large conjugated core structure. The synthesis takes advantage of dehydro-Diels−Alder reactions as a powerful and highly efficient method to access the polycyclic conjugated system. The functionalized rubicene derivatives are then characterized by optical, electrochemical and computational methods. This work contributes to discovery of potential candidates for innovative n-type organic semiconductors. In chapter 4, synthetic studies toward a carbon nanobelt – [12]cyclacene are performed. Though previous reports have made significant achievements in the construction of a macrocyclic framework, however, late-stage modification to install the fully conjugated structure is proved to be challenging. In this work, a new strategy involving a thermally-driven cheletropic rearrangement is proposed to address the late-stage modification issue. In the effort towards the macrocycle synthesis, an advanced intermediate has been successfully obtained in a stereoselective manner via multiple stereoselective Diels−Alder reactions. The selectivity is attributed to the careful design of precursors, which afforded the desired products through a sterically favored reaction pathway. A detailed examination of the proposed synthetic route as well as the proposal of a more convenient route are illustrated in the end.
  • Thumbnail Image
    Item
    The FSRS data of crystalline halogen-substituted rubrene derivatives under different excitation conditions taken in the Frontiera lab at the University of Minnesota in 2022
    (2024-05-16) Clapham, Margaret L; Das, Aritra; Douglas, Christopher J; Frontiera, Renee R; rrf@umn.edu; Frontiera, Renee R; University of Minnesota Frontiera Lab
    These are the FSRS data files of crystalline halogen-substituted rubrene derivatives under different excitation conditions, taken in the Frontiera lab at the University of Minnesota in 2022. This data is released to support a publication submitted to the Journal of the American Chemical Society entitled "Killer Phonon Caught: Femtosecond Stimulated Raman Spectroscopy Identifies Phonon-Induced Control of Photophysics in Rubrene Derivatives".
  • Thumbnail Image
    Item
    Time-of-Flight Investigation of Charge Carrier Mobilities in Oligoacene Single Crystals
    (2017-08) Lidberg, Russell
    Organic semiconductors remain an active area of research due to their unique mechanical and opto-electronic properties. The charge transport properties of organic semiconductors are dependent on their molecular packing structures. A fundamental understanding of the charge transport and device physics on a microscopic scale remains a central focus of discussion. Models and theories have been based on the understanding derived from inorganic systems, but these tend not to hold for organic semiconductors. Single crystals of small conjugated oligoacenes, with high chemical purity and molecular structural order, can be model systems in the study of the relationship between molecular packing and carrier charge transport. The ability to probe intrinsic charge transport, not influenced by environmental factors or measurement techniques, plays a fundamental role in gaining a deeper understanding of the factors affecting charge transport. Time of flight (TOF) is an experimental technique used for charge carrier mobility studies that minimizes the external factors affecting charge transport. TOF also has the potential to study both bulk (vertical) and surface (lateral) charge carrier transport in organic semiconductors. This work reports the charge carrier mobility in single crystals of tetracene and rubrene using vertical and lateral field TOF (LFTOF). TOF instrumentation was designed and constructed. Room temperature vertical TOF hole mobility results in the c-direction for tetracene single crystals were acquired as a function of electric field (µc ≈ 1.3 cm2/Vs at 296 K). Bulk TOF hole charge carrier in rubrene single crystal as a function of temperature and electric field were acquired with an average value of 0.29 cm2/Vs at 296 K increasing to 0.70 cm2/Vs at 180 K and demonstrated an inverse power law temperature dependence, ‘band-like’ transport, in the c-axis direction. The use of LFTOF to study transport on the surface of single crystal organic semiconductors was demonstrated. LFTOF hole mobilities of 0.8 cm2/Vs at 296 K were in the range of reported field effect transistor mobility results. An overview of organic semiconductors and traditional transport models along with emerging transport models for organic semiconductors is presented.