Influences of substitution on electronic structures of oligofluorenes

Abstract

The influences of substitutions on the electronic structures of oligofluorenes were systematically investigated. Electronic states of oligofluorenes with various types of C9 substitutions were studied by both ultraviolet photoemission spectroscopy and theoretical calculation. It is found that the substituents could have significant interaction with the backbone and substantially modify the electronic structures of oligofluorenes, depending on the types of substitutions. Consequently, the electronic properties that would affect the operations of electronic devices also considerably depend on the substitutions of the oligofluorenes.

Electronic and chemical properties of cathode structures using 4,7-diphenyl-1,10-phenanthroline doped with rubidium carbonate as electron injection layers

“…The theoretical density of states or simulated UPS spectra were then calculated by convoluting the molecular energy levels with Gaussian function using the full width at half maximum of 0.5 eV, which represents the broadening of discrete molecular levels due to the amorphous nature of organic films, vibronic origins, and instrumental broadening. 18,19 III. RESULTS AND DISCUSSION Figure 1 shows the performance of devices with current versus voltage curves in log scale.…”

Development of Materials for Blue Organic Light Emitting Devices

“…[20] Also, in a bid to study the substitution effect on the electronic structures of oligofluorenes, terfluorenes B3, T3 and E3, we scrutinized their properties with the help of ultraviolet photoemission spectroscopy (UPS) and quantum chemical calculations. [21] The valence-band spectra, for E3 and T3 were found to be fairly similar for binding energies < 4 eV, which clearly indicated that the first few HOMOs of T3 and E3 evolved from the parent terfluorene backbone and that both alkyl and aryl substituents probably played very less significant role in the frontier molecular orbitals (FMOs). Thus, the tetrahedral carbon (C9) of fluorene could serve as an efficient insulating spacer hindering the communication between the substitution and the backbone.…”

“…Thus, significant variations in UPS spectra were observed for oligofluorenes with different substitution moieties. [21] In an innovative approach, by employing the spectroscopic ellipsometry, the behavior of molecular reorientation by annealing amorphous thin films of a terfluorene compound (T3) close to or above its T g was examined. [22] The molecular reorientation was found to yield changes in the inplane optical constants, and this could subsequently affect the wave-guiding modes of a thin-film slab waveguide.…”

“…(a) Calculated and experimental UPS valence spectra of the compounds, E3, T3, and B3. Reproduced from Ref 21. with permission from the American Institute of Physics.…”

Fluorene-Based Conjugated Oligomers for Organic Photonics and Electronics

“…10 for a representative example). In addition, the electrochemically inactive substituents at fluorene's C-9 position have an insignificant effect on the energy levels associated with the backbone [171], as shown by ultraviolet photoemission spectroscopy (UPS), which is expected of electronic decoupling. The exception to this rule is a spirofluorene linkage, which does influence the energy levels to some degree through spiroconjugation [171].…”