Excited state dynamics and exciton diffusion in triphenylamine/dicyanovinyl push-pull small molecule for organic optoelectronics

Triphenylamine-based small push-pull molecules have recently attracted substantial research attention due to their unique optoelectronic properties. Here, we investigate the excited state de-excitation dynamics and exciton diffusion in TPA-T-DCV-Ph-F small molecule, having simple chemical structure with asymmetrical architecture and end-capped with electron-withdrawing p-fluorodicyanovinyl group. The excited state lifetime in diluted solutions (0.04 ns in toluene and 0.4 ns in chloroform) are found to be surprisingly shorter compared to the solid state (3 ns in PMMA matrix). Time-dependent density functional theory indicates that this behavior originates from non-radiative relaxation of the excited state through a conical intersection between the ground and singlet excited state potential energy surfaces. Exciton diffusion length of similar to 16 nm in solution processed films was retrieved by employing time-resolved photoluminescence volume quenching measurements with Monte Carlo simulations. As means of investigating the device performance of TPA-T-DCV-Ph-F, we manufactured solution and vacuum processed bulk heterojunction solar cells that yielded efficiencies of similar to 1.5% and similar to 3.7%, respectively. Our findings demonstrate that the short lifetime in solutions does not hinder per se long exciton diffusion length in films thereby granting applications of TPA-T-DCV-Ph-F and similar push-pull molecules in vacuum and solution processable devices

A Biocompatible Colorimetric Triphenylamine- Dicyanovinyl Conjugated Fluorescent Probe for Selective and Sensitive Detection of Cyanide Ion in Aqueous Media and Living Cells

A colorimetric and turn-on fluorescent probe 1 bearing triphenylamine-thiophene and dicyanovinyl groups has been synthesized and used to detect cyanide anion via a nucleophilic addition reaction. Probe 1 exhibited prominent selectivity and sensitivity towards CN− in aqueous media, even in the presence of other anions such as S2−, HS−, SO32−, S2O32−, S2O82−, I−, Br−, Cl−, F−, NO2−, N3−, SO42−, SCN−, HCO3−, CO32− and AcO−. Moreover, a low detection limit (LOD, 51 nM) was observed. In addition, good cell membrane permeability and low cytotoxicity to HeLa cells were also observed, suggesting its promising potential in bio-imaging

A Biocompatible Colorimetric Triphenylamine- Dicyanovinyl Conjugated Fluorescent Probe for Selective and Sensitive Detection of Cyanide Ion in Aqueous Media and Living Cells

A colorimetric and turn-on fluorescent probe 1 bearing triphenylamine-thiophene and dicyanovinyl groups has been synthesized and used to detect cyanide anion via a nucleophilic addition reaction. Probe 1 exhibited prominent selectivity and sensitivity towards CN− in aqueous media, even in the presence of other anions such as S2−, HS−, SO32−, S2O32−, S2O82−, I−, Br−, Cl−, F−, NO2−, N3−, SO42−, SCN−, HCO3−, CO32− and AcO−. Moreover, a low detection limit (LOD, 51 nM) was observed. In addition, good cell membrane permeability and low cytotoxicity to HeLa cells were also observed, suggesting its promising potential in bio-imaging

Exciton Dynamics and Charge Carrier Generation in Organic Semiconductors

The ever-increasing demand for cleaner sources of energy calls for inexpensive and highly efficient solar cells. Solution- and vacuum-processable organic solar cells have gained significant attention as an attractive source of energy owing to their continuously rising power conversion efficiency, low cost, thin device structure, and mechanical flexibility. The absorption of light in organic solar cells generates a strongly bound electron-hole pair called an exciton. To efficiently dissociate the exciton into charges, a heterojunction composed of electron donating and accepting materials with suitable energy levels is typically used to provide the driving force needed to overcome the Coulomb attraction between the electron-hole pair. The photon-to-charge conversion in organic solar cells is a complex process that is subject to losses; hence, it is critical to carefully monitor every step from photon-to-charge conversion, such as exciton photogeneration, exciton diffusion towards the donor-acceptor interface, and exciton dissociation into charges. This thesis sheds light on the photon-to-charge conversion process in organic photovoltaics using a multi-disciplinary approach that combines results from steady-state and time-resolved spectroscopy, and Monte Carlo simulations