Recently, decreasing the amount of indium (In) element in the indium tin oxide (ITO) used for transparent conductive oxide (TCO) thin film has become necessary for cost reduction. One possible approach to this problem is using printed ITO thin film instead of sputtered. Previous studies showed potential for printed ITO thin films as the TCO layer. However, nothing has been reported on the reliability of printed ITO thin films. Therefore, in this study, the reliability of printed ITO thin films was characterized. ITO nanoparticle ink was fabricated and printed onto a glass substrate followed by heating at 400 degrees C. After measurement of the initial values of sheet resistance and optical transmittance of the printed ITO thin films, their reliabilities were characterized with an isothermal-isohumidity test for 500 hours at 85 degrees C and 85% RH, a thermal shock test for 1,000 cycles between 125 degrees C and -40 degrees C, and a high temperature storage test for 500 hours at 125 degrees C. The same properties were investigated after the tests. Printed ITO thin films showed stable properties despite extremely thermal and humid conditions. Sheet resistances of the printed ITO thin films changed slightly from 435 omega/square to 735 omega/square 507 omega/square and 442 omega/square after the tests, respectively. Optical transmittances of the printed ITO thin films were slightly changed from 84.74% to 81.86%, 88.03% and 88.26% after the tests, respectively. These test results suggest the stability of printed ITO thin film despite extreme environments.
To realize flexible and wearable electronic devices in the future, it is important to develop flexible transparent electrodes while replacing indium tin oxide‐based transparent electrodes. Herein, a highly conductive transparent electrode based on hybrid materials of MXene nanosheet films and Ag nanowires (AgNWs) is reported, which synergistically combines the advantageous properties of each material. MXene/AgNW/colorless polyimide (cPI) hybrid electrode is prepared utilizing reverse sequential processing of MXene nanosheets and AgNWs and exhibits significantly improved conductivity and transmittance compared with the MXene/cPI electrode. Furthermore, owing to the abundant hydrophilic termination groups (‐O and ‐OH) on the MXene surface, the MXene/AgNW/cPI hybrid electrode shows hydrophilic surface properties and a highly uniform film. Therefore, the MXene/AgNW/cPI hybrid electrode exhibits higher transmittance at 550 nm to 79% than MXene/cPI electrode (59%) and considerably lower sheet resistance (13.08 ohm sq −1 ) than MXene/cPI electrode (113.6 ohm sq −1 ). Flexible organic photovoltaic devices fabricated with MXene/AgNW/cPI hybrid electrode achieve higher power conversion efficiency of 10.3% compared with 6.70% of the corresponding MXene/cPI electrode. These results provide the great potential of Ti 3 C 2 ‐based MXene hybrid electrode as a flexible transparent electrode, paving the way for various and wider range of applications include solar cells and light‐emitting diodes.
As the interest in foldable smartphones recently launched onto the market shifts toward the next generation of flexible electronics, the development of ultrathin devices is gaining considerable attention. The strain formed on the surfaces of film-based devices approximates the film thickness divided by twice the radius of curvature; therefore, the use of an ultrathin substrate is the key for the development of next generation foldable devices. However, the stiffness of ultrathin films is extremely low; thus, it cannot be easily used directly as a substrate for device fabrication. Therefore, these films generally undergo device manufacturing processes while being attached to a rigid substrate such as glass and are peeled from the rigid substrate after the process is finished. Thus, the initial adhesion of the adhesive used to fix the film to the temporary substrate should be strong, and after the process is completed, the adhesion must be lessened to enable soft peeling. In this study, we succeeded in developing a novel pressure-sensitive adhesive (PSA) whose adhesive strength can be severely reduced by water treatment. Accordingly, considering that amphiphilic oligomers promote water absorption through hydrogen bonding to water, amphiphilic oligomers were mixed with an acrylic polymer to prepare the water-responsive PSA (wr-PSA). The adhesion strength of the wr-PSA in the early stage, which reached 382(±22) N/m, dramatically dropped to 9(±2) N/m after a water immersion test. Using the wr-PSA, a 1.4 μm-thick polyethylene terephthalate film coated with Ag nanowires was softly peeled off from the glass after being immersed in warm water. In addition, the adhesion reduced by the immersion in water was recovered again when the water absorbed by the adhesive was dried. This implies that the developed adhesive can be reusable.
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