Transparent Conductive Coatings by Printing Coffee Ring Arrays Obtained at Room Temperature

Abstract

We report here a concept for utilization of the "coffee ring effect" and inkjet printing to obtain transparent conductive patterns, which can replace the widely used transparent conductive oxides, such as ITO. The transparent conductive coating is achieved by forming a 2-D array of interconnected metallic rings. The rim of the individual rings is less than 10 microm in width and less than 300 nm in height, surrounding a "hole" with a diameter of about 150 microm; therefore the whole array of the interconnected rings is almost invisible to the naked eye. The rims of the rings are composed of self-assembled, closely packed silver nanoparticles, which make the individual rings and the resulting array electrically conductive. The resulting arrays of rings have a transparency of 95%; resistivity of 0.5 cm(2) was 4 +/- 0.5 Omega/, which is better than conventional ITO transparent thin films. The silver rings and arrays are fabricated by a very simple, low cost process, based on inkjet printing of a dispersion of 0.5 wt % silver nanoparticles (approximately 20 nm diameter) on plastic substrates. The performance of this transparent conductive coating was demonstrated by using it as an electrode for a plastic electroluminescent device, demonstrating the applicability of this concept in plastics electronics. It is expected that such transparent conductive coatings can be used in a wide range of applications such as displays (LCD, plasma, touch screens, e-paper), lighting devices (electroluminescence, OLED), and solar cells.

Comparative Study of the Silver Nano-/Microstructures Deposited from Aerosol and Fog

“…At the same timeit was found that the silver NMS's with sizes from 0.5 to 20 nm are uniformly distributed on the substrate surface that is consistent with the ideas of the "coffee stains" model [8] [9] [10].…”

“…A promising approach to solve this problem may be thecreation of the metallic NMS precipitates formed during the evaporation of the micro-droplets from the metallic NMP colloidal solutions in various solvents [8] [9].…”

“…In the given case, depending on the conditions of the evaporation process [10], the metallic NMP deposits can exist either in the form of solid spots (this situation is considered in the "coffee stains" model [8]), or form of ring structure.…”

“…According to the research [8] [9] [10], the concerned method of the metallic NMS preparation can have many practical applications such as production of plasmon resonance sensors, catalytic surfaces, etc. The different forms of the received metallic NMS are due to the occurrence of the sedimentation processes in the highly non-equilibrium conditions which lead to the development of the self-organization.…”

Transparent Electrodes for Efficient Optoelectronics

“…One consists of the formation of transparent conductive grid patterns by self-assembly of Ag nanoparticles deposited by ink-jet printing. [96] Another approach, closer to the standard one using macroscopic metal Conductivity in relation to synthesis temperature (or annealing temperature) for selected transparent n-type and p-type conductors reported in literature. The color bar represents the absorption coefficient (averaged from 400-700 nm), with white the lowest (most transparent) and blue the highest (least transparent).…”