Photophysical and Photoconductive Properties of Novel Organic Semiconductors

Optical, Fluorescent, and (Photo)conductive Properties of High-Performance Functionalized Pentacene and Anthradithiophene Derivatives

“…Regardless of the film thickness, ADT-TIPS-F films showed a more pronounced vibronic structure of the fluorescence spectra than ADT-TES-F and ADT-TIPS-CN. The differences observed in fluorescence spectra of films compared to those in solutions are due to intermolecular interactions leading to a formation of molecular aggregates (whose properties depend on the degree of molecular order, size, and intermolecular coupling). − This is further supported by our observations that the fluorescence spectra of molecules under study embedded in low concentrations in PMMA matrix yielded spectra identical to those of solutions in Figure b, as expected from noninteracting molecules . Although all materials studied could be prone to aggregate formation due to their π-stacking properties, , fluorescent properties of aggregates significantly depended on the material.…”

“…Upon excitation with 400 nm 100 fs pulses, all samples showed fast photoresponse, with the risetime of about 30 ps, limited by the time resolution of our setup, , which indicates fast charge carrier photogeneration in these materials. ,, Transient photocurrents obtained in ADT-TIPS-F and ADT-TES-F films on Au electrodes upon excitation with 400 nm pulses at the fluence of ∼5 μJ/cm 2 and average electric field ( E ) of 4 × 10 4 V/cm are shown in Figure . In all polycrystalline films, transient photocurrents exhibited behavior previously observed in several organic crystals: ,, fast initial decay, most likely due to initial carrier trapping and recombination, followed by a slow component that can be fitted with a power-law function ( I ph ∼ t −β ) with β ≈ 0.2−0.6, depending on the sample and on the material, over at least 3 orders of magnitude (inset of Figure ) .…”

“…Transient Photocurrent. Upon excitation with 400 nm 100 fs pulses, all samples showed fast photoresponse, with the risetime of about 30 ps, limited by the time resolution of our setup, 15,39 which indicates fast charge carrier photogeneration in these materials. 13,29,48 Transient photocurrents obtained in ADT-TIPS-F and ADT-TES-F films on Au electrodes upon excitation with 400 nm pulses at the fluence of ∼5 µJ/cm 2 and average electric field (E) of 4 × 10 4 V/cm are shown in Figure 7.…”

“…[36][37][38] This is further supported by our observations that the fluorescence spectra of molecules under study embedded in low concentrations in PMMA matrix yielded spectra identical to those of solutions in Figure 1b, as expected from noninteracting molecules. 39 Although all materials studied could be prone to aggregate formation due to their π-stacking properties, 7,25 fluorescent properties of aggregates significantly depended on the material. For example, at room temperature, thin films of ADT-TIPS-F and ADT-TES-F were highly fluorescent, with QYs (Φ f,film ) of at least 40-50% depending on the film thickness and morphology.…”

Temperature dependence of exciton and charge carrier dynamics in organic thin films

“…Spectra of isolated ADT-TES-F molecules (either in solution or in a solid matrix such as PMMA) exhibit exciton coupling to a vibrational mode with an effective wave number ω eff of ~1400 cm -1 (0.173 eV), characterized by the Huang-Rhys factor S of 0.6 and a Gaussian width σ abs of the 0-0 line of about 235 cm -1 (0.029 eV). 5,8,9,[23][24][25] Spin-coated ADT-TES-F films prepared as described in Section II.A exhibited absorption spectra shown in Fig.2(a).…”