Thomas M. Kraft

Formulations ternaires d'encre de mélange pour fabriquer les piles solaires organiques par l'intermédiaire de l'impression de jet d'encre: L’objectif final de la thèse est l'impression de la couche photo-active ternaire d'une cellule solaire organique en utilisant deux approches: l'une concerne l'apport de nanotubes de carbone (SWCNT) pour améliorer les propriétés de transport, l'autre concerne la préparation de mélanges ternaires de matériaux pour contrôler la couleur des cellules. Les encres pour la couche active incluant des SWCNT fonctionnalisés sont composées d’un donneur d'électron (polymère) (poly(3-hexylthiophène), [P3HT]) et d’un accepteur d'électron ( [6,6]-phényl C61-butyrique ester méthylique d'acide [PCBM]) et ont été développées pour la fabrication de cellules inversées. Ces cellules sont réalisées sur substrats de verre pour l'optimisation de leurs performances, puis sur substrats plastiques pour les applications. Diverses couches d'interfaces ont été testées, qui incluent l'oxyde de zinc (ZnO, couches obtenues par pulvérisation ionique (IBS) ou à partir de solutions de nanoparticules) pour la couche de transport d'électrons et le PEDOT:PSS, le P3MEET, le V2O5 et le MoO3 pour la couche de transport de trous. Des essais ont été effectués avec et sans CNT afin d’étudier leur impact sur les performances. Des résultats similaires sont obtenus dans les deux cas. Il était attendu que les CNT améliorent les performances, ce qui n’a pas été observé pour le moment. Des travaux supplémentaires sont donc nécessaires au niveau de la formulation de la couche active.Avec trois polymères de couleur rouge (P3HT), bleu (B1) et vert (G1), nous avons préparé des mélanges ternaires efficaces permettant l'obtention de couleurs jusque là indisponibles . Nous avons fait une étude sur le piégeage et les mécanismes de diodes parallèles associés aux mélanges. En général, nous avons constaté que les mélanges ternaires de polymères bleu et vert peuvent être décrits par une mécanisme de diodes parallèles, sans entrainer de perte de performances, ce qui n'est pas possible pour les systèmes P3HT:B1 :PCBM et P3HT:G1:PCBM qui se piègent mutuellement. L’objectif final du projet est l'impression de la couche photo-active ternaire d'une cellule solaire organique, composites ternaires (polymère:polymères:acceptor) ou dopés avec les SWCNT. Cette étape nécessite encore des développements futurs.

A key aspect of printed electronics manufacturing is layer-layer registration and potential deformation of the substrate during processing (e.g. printing) which involves thermal treatment under tension or steps without any tension (e.g. surface mount hybrid integration of electronics). The influence of thermal processing on the registration control and material interfaces for printed and hybrid processing was evaluated on a pilot printing line using roll-to-roll screen-printed silver microflakes and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) inks. The registration was not fully stabilized on polyethylene terephthalate (PET) whereas on thermally pre-treated PET (PET_t) it reached ±60 µm accuracy in the machine direction (MD) and ±100 µm in the cross-machine direction (CD) after settling. The print on PET deviated 0.18% in MD and −0.01% in CD, implying that the print dimensions were changing along the MD elongation, whereas the changes on PET_t occurred during the pre-treatment, thus, the print deviated only −0.01% in MD and 0.08% in CD. Silver-substrate interface obtained good adhesion, however partial delamination was detected after thermal post-treatment at zero tension, most likely due to substrate shrinkage. Differences in the thermal response may partially delaminate the silver. Delamination of PEDOT:PSS was not observed, which may be related to its polymeric nature. Silver resistance on PET was 8% higher than on PET_t in MD, due to the elongation of the PET that occurs during print curing. Respectively, the silver resistance on PET was 2% lower in CD, with the dimensions slightly below the nominal layout value. Thermal post-treatment at zero tension reduced the resistance on both substrates, being greater in the MD as well as the substrate shrinkage. The impacts of thermal treatment are particularly important if the hybrid electronics processing is utilizing manufacturing lines with different web tension, such as printing and surface mount technology assembly, since the dimensional changes of the substrate can cause significant reduction in accuracy and reliability.

Printed electronics (PE) have provided new material and application opportunities for devices and systems as well as new manufacturing routes that all need to be considered for commercialization. This paper introduces a case study with universally relevant manufacturing processes and applications in the PE area, focusing on the Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) of the Personal Activity Monitor (PAM) device. In the study, the PAM device's most important costs and environmental impacts during the prototype pilot production and device use phases are identified and assessed. Additionally, the potential environmental impacts of post‐consumption scenarios are considered. The LCA results indicate that the roll‐to‐roll (R2R) assembly of electronics and the R2R injection over‐molding are generally the most prominent production process steps affecting the results. From the LCC perspective, the capitial expenditure (CAPEX) contributor is the R2R assembly pilot line, due to its high investment cost and long operating time compare to other production assets. The traditional electronic components are the major operating expenditures (OPEX), especially the microcontroller units (MCUs) and accelerometers, in contrast to the low impact from the printed electronics. There are several advantages to applying LCA and LCC since they provide explanations of the relationships between cost, environmental, design, and manufacturing characteristics.

The design and synthesis of three star‐shaped nonfullerene (NFA) acceptors, TPA‐2T‐INCN, TPA‐2T‐BAB, and TPA‐T‐INCN, based on a triphenylamine (TPA) core and linked through π‐conjugated thiophene (T) spacers to different terminal units (3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene) malononitrile, INCN, and 1,3‐dimethylbarbituric acid, BAB), are reported. These materials are blended with the widely used poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) donor polymer and tested in flexible organic photovoltaics (OPVs). The NFAs capped with the strong electron‐withdrawing INCN unit perform best in OPVs. Both P3HT:TPA‐T‐INCN and P3HT:TPA‐2T‐INCN blends also show the highest photoluminescence quenching efficiency (95.8% and 92.6%, respectively). Surprisingly, when reducing the number of T spacers from 2 to 1, the solubility of the NFAs in o‐dichlorobenzene increases, leading to easier processing during the OPV fabrication and better surface morphology. This explains the best performance of TPA‐T‐INCN‐based blends in OPVs, with a champion power conversion efficiency of 1.13%.

The demand for flexible large area optoelectronic devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs) is growing. Roll-to-roll (R2R) printing enables cost-efficient industrial production of optoelectronic devices. The performance of electronic devices may significantly suffer from local electrical defects. The dark lock-in infrared thermography (DLIT) method is an effective non-destructive testing (NDT) tool to identify such defects as hot spots. In this study, a DLIT inspection system was applied to visualize the defects of R2R printed silver conductors on flexible plastic substrates. A two-stage automated defect recognition (ADR) methodology was proposed to detect and localize two types of typical electrical defects, which are caused by complete or partial breaks on the printed conductive wires, based on localized segmentation and thresholding methods.

For the first time, the necessity to thermally pre-treat ubiquitously used PET substrates for printed electronics, to improve dimensional stability during manufacturing, is clearly defined. The experimental results have proven this phenomenon for both roll-to-roll (R2R) and sheet-to-sheet (S2S) processing of printed electronics. The next generation of electronics manufacturing has pushed the boundaries for low-cost, flexible, printed, and mass produced electronic components and systems. A driving force, and enabling production method, are the R2R printing presses. However, to produce electronics with increasing complexity and high yield in volume production, one must have a highly accurate process. In this article, R2R processing accuracy of printed electronics is evaluated from the point of dimensional accuracy of the flexible polyester substrate (DuPont Teijin Films’ PET Melinex ST504 with and without indium tin oxide, Melinex ST506, and Melinex PCS), precision of printing, and accuracy of layer-to-layer registration with stages that involve tension and elevated temperatures. This study has confirmed that dimensional changes during R2R processing will occur only in the first processing stage and that if a thermal pre-treatment run for the substrate is made—at identical temperature and tension of the processing stage—there is improved stability originating from a new-level strain in the crystalline PET film structure and freezing it in at the tensions and temperatures it is exposed to (i.e. 1400 μm machine direction stretching reduced to 8 μm). Furthermore, it is explained how the dimensional accuracy can be improved and reproducibly maintained in multilayer printing of electronics devices such as organic photovoltaics (OPV). These devices provide a valuable baseline of how the layer-to-layer alignment accuracy plays a crucial role in fully printed electronics devices, which lessons can be applied in all aspects of this field including hybrid systems and system fabrication involving multiple processing methods.

The industrialization of perovskite solar cells relies on solving intrinsic‐to‐material issues. To reach record efficiencies perovskite deposition needs to be finely adjusted by multi‐step processes, in a humidity free glove‐box environment and by means of hardly scalable techniques often associated with toxic solvents and anti‐solvent dripping/bath. Herein, the use of polymeric material is proposed to deposit perovskite layers with easy processability. To the scope, a starch‐polymer/perovskite composite is developed to suit slot‐die coating technique requirement, allowing the deposition of hybrid halide perovskite material in a single straightforward step without the use of toxic solvents, and in uncontrolled humid environment (RH up to 70 %). The starch‐polymer increases the viscosity of the perovskite precursor solutions and delays the perovskite crystallization that results in the formation of perovskite films at mild temperature (60 °C) with good morphology. These innovative inks enables the fabrication of flexible solar cells with p‐i‐n configuration featured by a power conversion efficiency higher than 3 %. . Overall, this approach can be exploited in the future to massively reduce perovskite manufacturing costs related to keeping the entire fabrication line at high‐temperature and under nitrogen or dry conditions.

The future of printed electronics involves advancements not only related to full system integration, but also lean process manufacturing. A critical aspect of this progress is developed in this study, which evaluates a highly flexible screen printed through-hole-via using silver microparticle inks, for applications in energy harvesting and storage modules. The printed vias’ fabrication and durability are evaluated by means of a double sided screen-printing method and repetitive (cyclic) bending tests. Vias, through 125-µm-thick PET foil, were laser cut (nominally 50, 100, 150, and 200 µm diameters) then filled, and simultaneously connected to adjacent vias by screen printing. To investigate the use of the printed via in a monolithic energy module, the vias were used for the fabrication of a flexible printed supercapacitor containing aqueous electrolyte and carbon electrodes. The results indicate that the lower viscosity silver ink (DuPont 5064H) fills the via less effectively than the higher viscosity ink (Asahi LS411AW), and as the via size increases (≥150 µm diameter) via walls are coated rather than filled. Conversely, the more viscous ink fills the via thoroughly and exhibited a 100% yield (1010 vias; 100 µm nominal via diameter) with the two-step direct screen-printing method. The 10-mm radius bending test showed no signs of via specific breakdown after 30,000 cycles. The results indicate that this via filling process is likely roll-to-roll compatible to enable multi-layered printed electronic devices.

The comparison of solution processed organic photovoltaics with two roll-to-roll coated electron transport layers (ETL), as well as printed grid or solid back electrodes provides insight into the future of R2R fabricated architectures. The variation in performance of the R2R slot-die coated zinc oxide (ZnO) versus the tin oxide (SnO ₂ ), showed a clear dependence on the spectrum of the illumination source. It was found that under indoor light conditions (200–1000 lux LED and fluorescent sources) the SnO ₂ outperformed the ZnO with highest efficiencies near 13% and 10% respectively. This is in contrast to results obtained under 1 Sun (AM 1.5) in which the cells fabricated with a ZnO ETL had a higher power conversion efficiency than those prepared with SnO ₂ . The results also confirm the significance of the layout of the printed silver back contact; in which cells with the grid structure outperformed those with full coverage by approximately 35% for ZnO and just under 10% for SnO ₂ (all light conditions). The combination of a R2R coating and S2S printing process to prepare modules with 8 cells in series (PET/ITO/SnO ₂ /PV2001:PCBM/PEDOT:PSS/silver grid) resulted in a PCE of 13.4% under indoor office light conditions.