Purpose This paper aims to describe two manufacturing techniques for selective patterning of Poly‐3‐4‐ethyleneoxythiophene/poly‐4‐sytrensulfonate (PEDOT/PSS) for flexible electronic applications. The paper also includes methods to tailor the electrical conductivity of the patterned polymeric films. Design/methodology/approach Line patterning and inkjet printing methods were used to pattern PEDOT/PSS onto mechanically flexible substrates including polyethylene terephthalate, polyimide and paper. Findings PEDOT/PSS thin films with controlled spatial resolution and strong adhesion passing a laboratory Scotch‐tape test were patterned onto flexible substrates using both line patterning and inkjet printing techniques. After annealing, the sheet resistivities of patterned PEDOT/PSS lines increased slightly. Treating the electrodes with ethylene glycol dramatically increased the electrical conductivity. Research limitations/implications There has been extensive work on selective deposition of solution processable active materials onto mechanically flexible substrates. Many techniques including line patterning and inkjet printing are currently being used to fabricate devices for flexible electronic applications. However, there is a need for tailoring the electrical conductivity of the patterned polymeric active materials. Originality/value In this study, two very cost effective methods for the selective deposition of the water soluble PEDOT/PSS onto flexible substrates with controlled spatial resolution and electrical conductivity are reported.
The
utilization of indium sulfide (In2S3)
photoelectrodes in an all-vanadium photoelectrochemical redox flow
battery system has been investigated. The In2S3-based photoelectrodes have been prepared via the ultrasonic spray
pyrolysis (USP) method. The thickness of the In2S3 photoelectrodes has been altered via increasing the pass number
of the USP nozzle from 25 to 75 passes. Each pass delivers 6 μL·cm–2 of the precursor solution. Within the scope of the
photoelectrochemical oxidation on the In2S3,
the vanadium couples of VO2+/V3+ have been proven
to be promising redox species. The maximum charge separation and quantum
efficiencies of 46% and 20% have been calculated, respectively.
This dissertation will outline solution processable materials and fabrication techniques to manufacture flexible electronic devices from them. Conductive ink formulations and inkjet printing of gold and silver on plastic substrates were examined. Line patterning and mask printing methods were also investigated as a means of selective metal deposition on various flexible substrate materials. These solution-based manufacturing methods provided deposition of silver, gold and copper with a controlled spatial resolution and a very high electrical conductivity. All of these procedures not only reduce fabrication cost but also eliminate the time-consuming production steps to make basic electronic circuit components. Solution processable semiconductor materials and their composite films were also studied in this research. Electrically conductive, ductile, thermally and mechanically stable composite films of polyaniline and sulfonated poly (arylene ether sulfone) were introduced. A simple chemical route was followed to prepare composite films. The electrical conductivity of the films was controlled by changing the weight percent of conductive filler. Temperature dependent DC conductivity studies showed that the Mott three dimensional hopping mechanism can be used to explain the conduction mechanism in composite films. A molecular interaction between polyaniline and sulfonated poly (arylene ether sulfone) has been proven by Fourier Transform Infrared Spectroscopy and thermogravimetric analysis. Inkjet printing and line patterning methods also have been used to fabricate polymer resistors and field effect transistors on flexible substrates from poly-3-4-ethyleneoxythiophene/poly-4-sytrensulfonate. Ethylene glycol treatment enhanced the conductivity of line patterned and inkjet printed polymer thin films about 900 and 350 times, respectively. Polymer field effect transistors showed the characteristics of traditional p-type transistors. Inkjet printing technology provided the transfer of semiconductor polymer on to flexible substrates including paper, with high resolution in just seconds.
In this work, we report a self-powered quasi-solid-state photodetector (PD) device prepared from flexible two-dimensional (2D) nanocomposites of a zinc oxide nanowire (ZnO-NW) in various weight percents (5, 10, 30, 50%) and Ti3C2Tx (MXene) paper, constructed with manganese (Mn)-doped zinc oxide nanorods (ZnO NRs) using an ionic gel electrolyte and carbon paper. All PD performance tests revealed that 5% ZnO-MXene-based devices were superior to the other samples. The maximum detectivity of 1.44 × 1013 Jones at 367 nm (0.1 mW cm–2) and zero bias was calculated for the 5% ZnO-MXene-based device. Additionally, a very high on/off ratio of nearly 106, which is approximately 35-fold higher than that of the 50% ZnO-MXene-based PDs, was achieved for 5% ZnO-MXene PD at a zero bias under 367 nm (2.52 mW cm–2) illumination. The rise time for this device was 9.25 ms. Furthermore, the PD device exhibited excellent stability by enduring 1000 s of light on/off cycles. As a result, a simple, compact, and cost-effective self-powered ZnO-NW:MXene-based PD configuration showed fast photoresponse and excellent detecting performance.
In this study, hydrogen gas generation for Proton Exchange Membrane Fuel Cells (PEMFC) was provided using precious catalysts. The critical catalyst concentration value and the effects of the catalyst amount and the sodium borohydride concentration on the hydrogen production rate were analyzed. PEMFC are one of the good candidates for powering unmanned air vehicles due to their low weight and high durability. They can provide longer flying times than lithium ion batteries. Our group manufactured a PEMFC producing 150 W power for unmanned air vehicles and optimized its performance. Moreover, the influence of the compression and the purge valve on and off time on fuel cell performance was investigated.
Photoelectrochemical solar cells (PEC) provide both harvesting and storage of the solar energy by converting it to chemical energy. In other words PEC systems convert sunlight into fuels by means of electrochemical reactions [1]. Total system efficiency of the PEC is directly affected by the performance of the working photoelectrode and the counter electrode. Here we investigated the influence of the morphology of the zinc oxide (ZnO) nanostructured photoelectrodes on the efficiency. ZnO photoelectrodes with nano-film, nanowire, and urchin-like morphologies have been used as working electrode in the three-electrode in one compartment cell configuration. Nano-films (ZnO-NF), 60 nm thick, have been deposited on the indium tin oxide (ITO) coated glass via physical vapor deposition. These films were used as the seeding layer to grow the ZnO nanowire arrays (ZnO-NW) by chemical bath deposition (CBD). Finally we fabricated the urchin-like nanostructures (ZnO-UL) on fluorine doped tin oxide coated (FTO) glass substrates by again CBD technique. In order to increase the coverage and the adhesion of the urchin-like structures we modified the surface of the FTO via hydroxylation process [2]. These electrodes were labeled as ZnO-H-UL. As expected, the light absorption of the nanowire and urchin-like structures was superior to the nanofilms. Therefore, nanowire formation slightly increased the current density under illumination at V Ag/AgCl =0V bias. On the other hand, current density increased approximately 10 3 times and reached to 3 mA/cm 2 for the ZnO-H-UL samples compare to the nano-films. Another drastic change was observed for the photoresponse, which is a measure of photo-generated current in the system. In other words photoresponse of the electrode can be calculated from the ratio of J ill -J dark to J dark , where J ill is the current density under illumination and J dark is the current density at dark. The maximum photoresponse of the ZnO-NF was 4.5 indicating almost no current change in dark and under illumination. However, this value was 55, 7.9x10 2 , and 1.2x10 3 for ZnO-NW, ZnO-UL and ZnO-H-UL electrodes, respectively. Enhancement in the photo generated current density for the urchin like structure could be related with the better light absorption and longer electron lifetime. According to our best knowledge this is the highest photoresponse reported in literature. Efficiency of the ZnO electrodes was calculated using the well known applied bias photon-to-current efficiency (ABPE) definition [3]. ABPE of the ZnO-NF and NW electrodes was 0.09 and 0.32 %, respectively. Efficiency of the ZnO electrodes increased with formation of needle like structures on the spherical bases. 0.65 and 0.87 % ABPE was observed for ZnO-UL and H-UL nanostructures, respectively. One can determine the overall PEC device efficiency by the ratio between the energy of the produced hydrogen and the total energy spent to accomplish the water splitting reaction [4]. PEC solar cells produced using ZnO-H-UL photoanode had the overall device efficiency of the 2.5%. Better photoresponse, photo current density, and the device efficiency of the ZnO-H-UL electrodes compare to the other nanostructures made them very favorable in PEC systems as working electrodes. References: [1] M. Gratzel, Nature 414 (2001) 338-344. [2] W. Zhang, D. Zhang, T. Fan, J. Gu, J. Ding, H. Wang, Q. Guo, H. Ogawa, Chem Mater 21 (2009) 33-40. [3] Z. Chen, T.F. Jaramillo, T.G. Deutsch, A. Kleiman-Shwarsctein, A.J. Forman, N. Gaillard, R. Garland, K. Takanabe, C. Heske, M. Sunkara, E.W. McFarland, K. Domen, E.L. Miller, J.A. Turner, H.N. Dinh, J.Mater Res 25 (2010) 3-16. [4] P. Dias, T. Lopes, L. Andrade, A. Mendes, J Power Sources 272 (2014) 567-580.
