Showing papers by "Roar R. Søndergaard published in 2013"

Roll‐to‐Roll fabrication of large area functional organic materials

Abstract: With the prospect of extremely fast manufacture of very low cost devices, organic electronics prepared by thin film processing techniques that are compatible with roll-to-roll (R2R) methods are presently receiving an increasing interest. Several technologies using organic thin films are at the point, where transfer from the laboratory to a more production-oriented environment is within reach. In this review, we aim at giving an overview of some of the R2R-compatible techniques that can be used in such a transfer, as well the current status of R2R application within some of the existing research fields such as organic photovoltaics, organic thin film transistors, light-emitting diodes, polymer electrolyte membrane fuel cells, and electrochromic devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Roll-to-Roll Inkjet Printing and Photonic Sintering of Electrodes for ITO Free Polymer Solar Cell Modules and Facile Product Integration

Abstract: Cell Modules and Facile Product Integration DTU Orbit (17/12/2018) Roll-to-Roll Inkjet Printing and Photonic Sintering of Electrodes for ITO Free Polymer Solar Cell Modules and Facile Product Integration Small polymer solar cell modules that are manufactured without indium-tin-oxide using only roll-to-roll printing and coating techniques under ambient conditions enable facile integration into a simple demonstrator (for example a laser pointer). Semitransparent front electrode grid structures prepared by roll-to-roll inkjet printing in conjunction with photonic sintering enabled preparation of complete modules on flexible substrates and subsequent integration of the modules into a laser pointer demonstrator.

Fast Inline Roll‐to‐Roll Printing for Indium‐Tin‐Oxide‐Free Polymer Solar Cells Using Automatic Registration

Abstract: carbon nanotubes [20] with varying success. However, only the report in Ref. [11] has demonstrated the potential to be sufficiently scaleable for the final substrate to be produced at a speed and cost allowing for its consideration as a serious candidate for R2R printing. Here we present a new flexible semitransparent substrate which, when used in the preparation of OPVs, provides similar performances to analogous modules prepared on ITOcovered substrates. [1] This “flextrode” substrate is suitable for inverted-structure OPVs and is based on a high-conductivity PEDOT:PSS layer, which is coated with zinc oxide. For larger areas a flexo-printed silver grid reduces sheet resistance. We demonstrate how the ITO-free electrode material can be processed at high speed by printing several layers at the same time using inline printing and coating. We show that a length of 1000 m is easily manufactured within a few hours having full 2-dimensional registration of the printed pattern. We see this as the first real candidate for a mass producible replacement for ITO, and to promote the use of such substrates in academic research, this substrate is made freely available.

Practical evaluation of organic polymer thermoelectrics by large-area R2R processing on flexible substrates

Abstract: Here, we present a process based on roll-to-roll (R2R) technology which allows for very fast processing of polymer thermoelectric (TE) devices and we furthermore demonstrate a simplified but more efficient way of serially connecting these devices by means of R2R thin-film processing. The new device architecture makes it possible to use only one TE material (opposed to two materials which are employed in well-known Peltier elements), and a total of 18,000 serially connected junctions were prepared by flexoprinting of silver electrodes and by rotary screen printing of poly(3,4-ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS) as the TE material. Testing of devices revealed that the new architecture clearly showed to be functioning as expected, but also pointed toward challenges for thin-film TE development which is the influence of the substrate thickness on the thermal gradient over a device and the currently low performance available. A life-cycle assessment (LCA) was carried out in order to evaluate the sustainability of the new architecture and to estimate the requirements for development of a successful technology.

Comparison of Fast Roll-to-Roll Flexographic, Inkjet, Flatbed, and Rotary Screen Printing of Metal Back Electrodes for Polymer Solar Cells

Abstract: Metal Back Electrodes for Polymer Solar Cells DTU Orbit (06/11/2019) Comparison of Fast Roll-to-Roll Flexographic, Inkjet, Flatbed, and Rotary Screen Printing of Metal Back Electrodes for Polymer Solar Cells The majority of polymer solar cells reported today employs processing under high vacuum for one or more of the layers in the solar cell stack. Most notably the highly conducting metal back electrode is almost exclusively applied by evaporation of the pure metal. While it is not impossible to envisage mass production of polymer solar cells using vacuum processing it does present some drawbacks in terms of both processing speed, capital investment in processing equipment technical yield and direct process energy. From this point of view it is clear that vacuum processed electrodes should be avoided and electrodes should be printable using methods that provide a high degree of accuracy and high technical yield. When considering large area polymer solar cells (i.e., not laboratory devices) a few reports have employed printable back electrodes mostly by use of silver formulations[1–4] but also carbon[5] and copper has been discussed whereas copper is unlikely to yield the necessary cost reduction and resistance to oxidation. Most reports have employed flatbed or rotary screen printing whereas other methods are available and described later on. The important question to answer is which technique is most suited for manufacture of polymer solar cell modules in terms of technical yield, materials use and processing speed? Evidently the back electrode has to be of high conductivity, which implies the use of a thick electrode. Therefore thick film printing techniques such as the screen printing techniques have proven excellent while they do present disadvantages in speed due to significant drying requirements but also they do require significant amounts of material.[2,6] In this paper we employ four different roll-to-roll (R2R) printing methods for printing silver back electrodes for polymer solar cell modules based on the IOne process which is a fully printable, indium-tin-oxide (ITO), and vacuum free technology that provide similar performance to ITO-based polymer solar cell modules when using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester ([60]PCBM) as the active layer. We analyze advantages and disadvantages for each method and also outline boundaries of their use and highlight a few areas where development could lead to disruptive progress for the polymer solar cell as a technology.

Comparison of UV-Curing, Hotmelt, and Pressure Sensitive Adhesive as Roll-to-Roll Encapsulation Methods for Polymer Solar Cells

Abstract: The most distinct advantage of the polymer solar cell is the possibility for roll-to-roll (R2R) fabrication compatibility based on printing and coating processes. The R2R encapsulation is the last crucial process step in the manufacturing workflow and is evaluated in this study. Polymer solar cell modules are directly printed on barrier foil and encapsulated with the same barrier foil either on the backside or on both sides of the device. The three lamination methods comprise of UV-curable epoxy resin, hotmelt, and pressure sensitive adhesive (PSA). It is shown that a single-sided encapsulation with UV-curable adhesive is enough to achieve the same or better lifetime than double-sided encapsulation with all the adhesives utilized here. This is mainly due to the good edge sealing effect of the thin adhesive with no edge bleaching after 900 h of constant illumination. Although the fabrication of the PSA method is the fastest method (in this study) it generates a considerable amount of waste (paper liner) and two lamination steps are required to achieve a sufficient lifetime. We conclude that UV-curing presents the largest advantages of all methods with a good upscaling potential and low embodied energy due to the possibility for single-sided encapsulation.

OPV for mobile applications: an evaluation of roll-to-roll processed indium and silver free polymer solar cells through analysis of life cycle, cost and layer quality using inline optical and functional inspection tools

Abstract: Organic photovoltaic modules have been evaluated for their integration in mobile electronic applications such as a laser pointer. An evaluation of roll-to-roll processed indium and silver free polymer solar cells has been carried out from different perspectives: life cycle assessment, cost analysis and layer quality evaluation using inline optical and functional inspection tools. The polymer solar cells were fabricated in credit card sized modules by three routes, and several encapsulation alternatives have been explored, with the aim to provide the simplest but functional protection against moisture and oxygen, which could deteriorate the performance of the cells. The analysis shows that ITO- and silver-free options are clearly advantageous in terms of energy embedded over the traditional modules, and that encapsulation must balance satisfying the protection requirements while having at the same time a low carbon footprint. From the economic perspective there is a huge reduction in the cost of the ITO- and silver-free options, reaching as low as 0.25 € for the OPV module. We used inspection tools such as a roll-to-roll inspection system to evaluate all processing steps during the fabrication and analyse the layers' quality and forecast whether a module will work or not and establish any misalignment of the printed pattern or defects in the layers that can affect the performance of the devices. This has been found to be a good tool to control the process and to increase the yield.

Fast printing of thin, large area, ITO free electrochromics on flexible barrier foil

Abstract: Processing of large area, indium tin oxide (ITO) free electrochromic (EC) devices has been carried out using roll-to-roll (R2R) processing. By use of very fine high-conductive silver grids with a hexagonal structure, it is possible to achieve good transparency of the electrode covered substrates and when used in EC devices switching times are similar to corresponding ITO devices. This is obtained without the uneven switching of larger areas, which is generally observed when using ITO because of its high-sheet resistance. The silver electrode structures for 18 × 18 cm2 devices can be processed at high speed (10 m/min) on PET by flexographic printing and the EC polymer ECP-Magenta as well as a minimal color changing polymer MCCP by slot-die coating, showing the potential for fast fabrication of large volumes of low-priced flexible EC devices by use of R2R processing techniques. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

Conductance Enhancement of InAs/InP Heterostructure Nanowires by Surface Functionalization with Oligo(phenylene vinylene)s

Abstract: We have investigated the electronic transport through 3 μm long, 45 nm diameter InAs nanowires comprising a 5 nm long InP segment as electronic barrier. After assembly of 12 nm long oligo(phenylene vinylene) derivative molecules onto these InAs/InP nanowires, we observed a pronounced, nonlinear I–V characteristic with significantly increased currents of up to 1 μA at 1 V bias, for a back-gate voltage of 3 V. As supported by our model calculations based on a nonequilibrium Green Function approach, we attribute this effect to charge transport through those surface-bound molecules, which electrically bridge both InAs regions across the embedded InP barrier.