Comprehensive Stability Improvement of Silver Nanowire Networks via Self-Assembled Mercapto Inhibitors

Abstract

Instability of silver nanowire (AgNW) has been regarded as a major obstacle to its practical applications in optoelectrical devices as transparent electrodes. Physical barrier layers such as polymer, metal, and graphene have been generally employed to improve the stability of AgNW in previous study. Herein, we first report self-assembled organothiols as an inhibitor for AgNW to achieve an overall enhancement in antioxidation, antisulfidation, thermal stability, and anti-electromigration. The self-assembled monolayers (SAMs) of phenyl azoles, methoxy silane, and methyl alkane were formed on the surface of AgNW via Ag−S covalent bond as barrier layers which provided protective effects against corrosives (e.g., O 2 , H 2 S). In particular, the decoration of 2-mercaptobenzimidazole (MBI) offered the best resistance to H 2 S and excellent stability under a high-temperature and high-humidity environment (85 °C and 85 RH %) for 4 months. Moreover, different SAMs exhibited a stabilizing or destabilizing effect on Plateau−Rayleigh instability of AgNW, which realized the tunability of degradation temperature of AgNWs, for example, increasing by ≥100 °C with MBI SAM or decreasing by ∼50 °C with octadecanethiol SAM compared with pristine AgNWs. Notably, the MBIdecorated AgNWs could survive at 400 °C which is by far the highest bearing temperature for solution-processed AgNW film. As a result, a transparent heater made of the MBI-AgNWs exhibited superior heating characteristics (higher working temperature and durability), as compared with the pristine AgNW-based heater. Our findings on the organothiols decoration not only provide a new paradigm in overall stability improvement of NW of noble metals but also show the potential in morphology controllability of metal NW.

Increasing Silver Nanowire Network Stability through Small Molecule Passivation

“…Instead of coating a passivating material over the entire electrode surface as in the paragraph above, coating the surfaces of the AgNWs only with an organic short molecule has many advantages. Functionalization of the metal nanowires with strongly bound ligands enhance their chemical stability, and in many cases does not affect the transparency and conductivity of an electrode [28,29,30]. It should also not have any effect on the electrode’s mechanical flexibility, and the process is cost-effective.…”

“…Liu et al recently tested the passivation abilities of several different organothiols. For example, with 2-mercaptobenzimidazole (MBI), the resistance increase of a AgNW network was limited to only 67% after 120 days [30]. However, these latter tests were performed in a chamber without exposure of the AgNWs to light.…”

“…Very recently, AgNWs were passivated with alkanethiolate (octadecanethiol, ODT), a similar molecule to MUA but with 18 carbon chains instead of 10, and having no acidic function at the molecule end [29,30]. An 18% resistance increase was measured after 30 days versus 169% for unpassivated nanowires.…”

“…Furthermore, the surface of a nanowire network cannot be covered in a non-conductive polymer if used in a solar cell or LED since the electrode is not electrically accessible. In a later study, the effectiveness of ODT was studied without embedding the nanowires in a resin, but only tests in the dark were performed whereas in applications, AgNW electrodes will absolutely be exposed to light [30].…”

Synthesis and Applications of Silver Nanowires for Transparent Conductive Films

“…Based on the well-formed Ag NWs, the TCE with high conductivity and high transparency is obtained, and this review will introduce several important preparation methods of TCE, such as spin coating [26,27], inkjet printing [28], and roll-to-roll (RTR) printing process [29,30]. On this basis, some common problems in the preparation process are discussed including high junction resistance [31], poor adhesion between Ag NWs and substrate [32], poor thermal stability and environmental stability of Ag NWs TCE [33]. These problems limit the production and applications of Ag NWs TCE.…”