Accelerated and outdoor weathering of silver nanowire transparent conductors under electrical stress in pseudo-modules

Abstract

In realistic applications, silver nanowires (AgNWs) are encapsulated in optoelectrical devices to function as transparent conductors and electrodes. Environmental stressors along with the essential electrical stress are inevitably harmful to the AgNWs inside the devices. Herein, to investigate the degradation behavior discrepancy between materials-level and device-level tests, we adopted pseudo-module to mimic the encapsulation. The pseudo-module allows the application of electrical stress and facilitates the interim specimen access for materials characterization through assembly-disassembly. Indoor accelerated and outdoor weathering tests with applied electrical stress to the pseudo-module encapsulated AgNW networks were performed. The impaired optoelectrical properties and morphological changes of AgNWs due to multiple or individual stressor(s) are investigated. Results indicate UVA exposure at elevated temperature coupled with electrical stress is responsible for the electrical failure of AgNW networks. Sulfidation that depresses optical transparency of AgNW networks is prone to occur at lower temperature. This work provides unambiguous degradation behaviors of AgNWs inside encapsulants, helping to improve the design of AgNWs related optoelectrical devices in the applications of solar irradiation environments.

Weathering and Material Characterization of ZTO/Ag/ZTO Coatings on Polyethylene Terephthalate Substrates for the Application of Flexible Transparent Conductors

“…The field test of outdoor weathering was performed using an under-glass exposure box conforming to ASTM G24 and G201 standards. The exposure site of the field tests was located on the campus of the Feng Chia University in Taiwan [9,19]. The outdoor weathering test was carried out for 92 days starting from 15 July 2021.…”

“…Recently, the technology of laminated coatings composed of oxide/metal/oxide (abbreviated as OMO) layers has reached commercialization level for mass production and commercial use for the requirements of flexible transparent conductive films. However, the durability and weatherability of the materials-including laminated nanofilms with a transparent conductive metal oxide/silver mesh/metal oxide structure and polymeric substrates-affect their performance [4][5][6][7][8][9]. The reliability of the fabricated optoelectrical components and devices is accordingly affected; therefore, the viability of widespread commercialization for flexible and printable optoelectronics is impeded.…”

“…On the other hand, as for the metal layer, the research results of Jeong et al show that doping with oxygen atoms in the silver interstitial sites can reduce the free energy of the interface for the silver mesh layer [7], greatly improving the ability of dewetting and material stability, and inhibiting thermal degradation. In addition, because ultraviolet (UV) light can easily decompose and recombine oxygen molecules in the environment to form stable oxygen atoms and ozone [8], UV light is inevitably an environmental factor that impairs the flexible transparent conductors of the laminated OMO structures and polymeric substrates [9]. However, the weatherability and stability problems caused by the effects of UV exposure at elevated temperatures have not been reported in any literature so far.…”