Pisist Kumnorkaew

PEDOT:PSS Nanofilms Fabricated by a Nonconventional Coating Method for Uses as Transparent Conducting Electrodes in Flexible Electrochromic Devices

Nanofilms of a polymer mixer of two ionomers, poly 3,4-ethylenedioxythiophene:poly(styrene sulfonic acid) (PEDOT:PSS), were used as conducting materials to develop transparent conducting electrodes. It was firstly found that convective deposition, a versatile and wide-area coating method, could be used for the coating and acid treatment of PEDOT:PSS films. Electrical conductivity of the PEDOT:PSS films was significantly enhanced up to 1814 S/cm by only one-time surface treatment by a mild acid solution (4 M methanesulfonic acid). This is because some PSS chains were removed out from the polymer mixer films without damage on the substrates. UV-vis-NIR spectroscopy, Raman spectroscopy, and cyclic voltammetry were used to characterize the acid-treated transparent conducting films. In this report, obtained transparent conducting PEDOT:PSS films on polyester substrates were used as flexible electrodes for fabrication of flexible electrochromic devices. Poly(3-hexylthiophene) (P3HT) was used as an active layer, which its color changed reversibly from transparent-light blue to purple with a small applied voltage (±3 V).

Preparation of Surlyn films reinforced with cellulose nanofibres and feasibility of applying the transparent composite films for organic photovoltaic encapsulation

This research concerns the development of Surlyn film reinforced with micro-/nanofibrillated celluloses (MFC) for use as an encapsulant in organic photovoltaic (OPV) cells. The aim of this work was to investigate the effects of fibre types and the mixing methods on the structure–properties of the composite films. Three types of cellulose micro/nanofibrils were prepared: the as-received MFC, the dispersed MFC and the esterified MFC. The fibres were mixed with Surlyn via an extrusion process, using two different mixing methods. It was found that the extent of fibre disintegration and tensile modulus of the composite films prepared by the master-batching process was superior to that of the composite system prepared by the direct mixing method. Using the esterified MFC as a reinforcement, compatibility between polymer and the fibre increased, accompanied with the improvement of the percentage elongation of the Surlyn composite film. The percentage of light transmittance of the Surlyn/MFC films was above 88, regardless of the fibre types and fibre concentrations. The water vapour transmission rate of the Surlyn/esterified MFC film was 65% lower than that of the neat Surlyn film. This contributed to the longer lifetime of the OPV encapsulated with the Surlyn/esterified MFC film.

Microspheres pattern forming using self-assembly template prepared by convective deposition

Stacks pattern of microspheres and nanoparticles can be deposited by layer-by-layer coating with several techniques. In this work, we fabricated two pattern monolayers of polystyrene microparticle by convective horizontal deposition. For initial layer, glass substrate was dragged with velocity of 25 μm/s and also applied horizontal vibration with frequency of 50 Hz in order to supply higher kinetic energy for better assembly. Sizes of polystyrene microparticles were 3.2 micrometer for this initial template coating. For the second layer, the microparticle size was varied with 0.93, 1.00, and 1.50 micrometer. The packing of the second layer was investigated by scanning electron microscope. The filling quality of second coating layer strongly depend on particle size and dragging velocity. For the same dragging speed, the microparticle of 0.93 micrometer trended to be well arrangement on the initial template with honeycomb pattern.

Improvement of Efficiency of Polymer-Zinc Oxide Hybrid Solar Cells Prepared by Rapid Convective Deposition

The aim of this research is to study improvement of power conversion efficiency (PCE) of organic-inorganic hybrid bulk heterostructure solar cell prepared by rapid convective deposition as a function of concentration of zinc oxide additive. The structure of hybrid solar cell used in this research is ITO/ZnO/P3HT:PC70BM:ZnO(nanoparticles)/MoO3/Au. By adding 5 mg/ml of ZnO nanoparticles in the active layer (P3HT:PC70BM), the PCE was increased from 0.46 to 1.09%. In order to reveal the origin of improving efficiency, surface morphology and optical properties of active layers were investigated by atomic force microscopy (AFM) and UV-Visible spectroscopy, respectively. The results clearly indicate that the enhancement of solar cell efficiency results from (i) the proper phase sepharation of electron donor and acceptor in the active layer and (ii) the better absorption of the active layer. This research work introduces an alternative way to improve solar cell efficiency by adding ZnO into active layer.