Spray Coating of Crack Templates for the Fabrication of Transparent Conductors and Heaters on Flat and Curved Surfaces

Abstract

Transparent conducting electrodes (TCEs) have been made on flat, flexible, and curved surfaces, following a crack template method in which a desired surface was uniformly spray-coated with a crackle precursor (CP) and metal (Ag) was deposited by vacuum evaporation. An acrylic resin (CP1) and a SiO2 nanoparticle-based dispersion (CP2) derived from commercial products served as CPs to produce U-shaped cracks in highly interconnected networks. The crack width and the density could be controlled by varying the spray conditions, resulting in varying template thicknesses. By depositing Ag in the crack regions of the templates, we have successfully produced Ag wire network TCEs on flat-flexible PET sheets, cylindrical glass tube, flask and lens surface with transmittance up to 86%, sheet resistance below 11 Ω/□ for electrothermal application. When used as a transparent heater by joule heating of the Ag network, AgCP1 and AgCP2 on PET showed high thermal resistance values of 515 and 409 °C cm(2)/W, respectively, with fast response (<20 s), requiring only low voltages (<5 V) to achieve uniform temperatures of ∼100 °C across large areas. Similar was the performance of the transparent heater on curved glass surfaces. Spray coating in the context of crack template is a powerful method for producing transparent heaters, which is shown for the first time in this work. AgCP1 with an invisible wire network is suited for use in proximity while AgCP2 wire network is ideal for use in large area displays viewed from a distance. Both exhibited excellent defrosting performance, even at cryogenic temperatures.

Towards low cost materials and methods for transparent electrodes

“…Uniformity of metal mesh distribution is evident from IR camera images of flexible heater fabricated on PET substrates (Figure 3e) [71 ]. Low power consuming large area defrosting window panel was demonstrated [74] in addition to curved surface applications [75]. An unusual transparent heater fabricated on a quartz substrate was shown to have high thermal stability and extraordinary thermal response [76 ].…”

High‐Performance Flexible Transparent Electrode with an Embedded Metal Mesh Fabricated by Cost‐Effective Solution Process

“…Accurate control of the FTTH temperature was achieved by adjusting the supplied voltage, as demonstrated in Figure 7 c. The video (Supporting Information Movie S1) displays the temperature distribution of the FTTH when tuning the supplied voltage. Compared with most published results, [ 54,[65][66][67][68][69][70][71][72] a lower power density requirement (<0.15 W cm −2 ), a rapid response (<2 s), and a lower operating voltage (<1 V) make our EMTE-based FTTH to be a unique device for broad applications.…”

“…b) Plot of transmittance versus sheet resistance for copper EMTEs with different mesh thickness, with calculated FoMs shown in the inset. c) Comparison of the FoMs of EMTEs with other published transparent electrodes (metal NW, [41][42][43][44][45][46][47][48] metal mesh, [19][20][21][22][23][24]35,[49][50][51][52][53][54][55][56][57][58] and hybrid [59][60][61][62][63] ) and industrial standards. [ 63 ] solar cell applications.…”

Highly flexible, stretchable, patternable, transparent copper fiber heater on a complex 3D surface

“…Above all, the most critical issue is the limited power (P) that can be supplied to such materials. This severely restricts the maximum attainable temperature (T s ), since T s ∝ P. For example, the temperature ranges of graphene heaters, silver nanowire heaters, and heaters utilizing hybrid materials combining graphene and silver nanowires are 100-206°C, [19][20][21] 48-160°C, [22][23][24][25][26][27] and up to 225°C, 28,29 respectively.…”