Optimization of Precursor Injection in an Atmospheric Pressure Plasma Jet System

Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition (AP PECVD) of thin films is a recently emerged technology, showing important advantages in comparison with the traditional and well established low pressure plasma enhanced deposition methods. The main benefit of AP-PECVD is the potential of cost efficient in-line production without expensive and bulky vacuum equipment. In this work, an innovative AP plasma jet system is investigated which serves as a pilot system for industrial scale equipment, the VITO PlasmaLine®. Applications include moisture/oxygen diffusion barriers as well as grease barriers, UV curing of coatings or chemical activation of a surface. For industrial application a high throughput (~ 100-1000 m/min) is critical in order to compete with conventional techniques, such as wet chemical coating. Barrier coating deposition by AP-PECVD on polymer substrates has been demonstrated to be superior to wet chemical coating, with less consumption of precursor material [1], though many technical challenges remain to obtain the desired (dynamic) growth rates. The pilot equipment utilizes a 0.5 mm double slit configuration with 1000-2000 W power input at a frequency of 40-50 kHz with N2 as the primary carrier gas. By utilizing the plasma afterglow remote from the source, uniform surface treatment can be achieved despite the filamentary discharge in the slits. Deposition on the electrodes is prevented by injection of precursor into the jet and because of the remote nature of the plasma source the thermal load on the substrate is minimized, making it ideally suited for treatment of polymers and paper. A key area for improvement and upscaling of the pilot system for industrial application is optimization of gaseous and liquid (aerosol) precursor injection. To this end, extensive characterization of the plasma jet is undertaken, including current-voltage, fast imaging and optical emission and absorption measurements, with focus on the dynamics of gaseous and aerosol precursor particles in the jet. For optimum control over the gas distribution and precursor injection, Computational Fluid Dynamic models are presented in conjunction with the experimental work

Synthesis And Characterization Of A Poly(1,3-dithienylisothianaphthene) Derivative For Bulk Heterojunction Photovoltaic Cells

The synthesis of a poly(1,3-dithienylisothianaphthene) (PDTITN) derivative obtained via oxidative polymerization of 5,6-dichloro-1,2-bis(3'-dodecylthienyl)isothianaphthene is described. PDTITN exhibits a band gap of 1.80-1.85 eV. The redox properties of PDTITN were characterized using cyclic voltammetry and spectroelectrochemistry. Photoexcitation of PDTITN results in photoluminescence (PL) in the near-IR region and the formation of a triplet state. In the presence of a methanofullerene (PCBM) as an electron acceptor, PL and triplet formation of PDTITN are quenched. In photovoltaic devices using blends of the polymer with PCBM, the observed incident-photon-to-collected-electron efficiency (IPCE) up to 24% at 400 nm and the 3 orders of magnitude increase of short circuit current as compared to the polymer alone prove the photoactivity of the PDTITN/PCBM blend in the device.