Allrounder Strategy of Using a Photocrosslinker for Photopatterning Transparent Silver Nanowire/PEDOT:PSS Electrodes

This work aims to develop transparent conductive materials for various applications such as next-generation displays, sunlight harvesting, lighting, and smart windows. These materials need to have high optical transparency, electrical conductivity, and mechanical flexibility. Additionally, they must exhibit environmental stability and be suitable for practical manufacturing processes. Silver nanowires (AgNWs) are considered promising candidates that meet these demanding requirements. AgNWs form a percolated network that offers high optical transparency and electrical conductivity. This network structure is also tolerant to mechanical deformation. Furthermore, Ag NWs can be dispersed in various solvents and applied to flexible substrates using solution-based methods.<br/> Despite these advantages, the widespread use of AgNWs in commercial applications has been limited. One key challenge is the need for scalable processing methods to create precise and high-throughput AgNW networks that meet industrial standards. One common approach is the surface-energy-controlled transfer printing of AgNW networks onto target substrates, but this method faces challenges related to uniformity and fidelity.<br/> Photolithography, a prominent microfabrication technology, is also considered a reliable and scalable patterning technique for AgNWs. However, traditional photolithography methods, involving pre-patterned photoresist and subsequent etching or lift-off processes, are not fully compatible with AgNW networks due to their porous nature and poor adhesion to substrates.<br/> To address these issues, we developed a direct photopatterning method for AgNW networks. This method requires only a small amount of photocrosslinking agent (&lt;3 wt%). A crosslinker, (oxybis(ethane-2,1-diyl))bis(oxy))bis(ethane-2,1-diyl)bis(4-azido-2,3,5,6-tetrafluorobenzoate (2Bx-4EO), was designed and synthesized to induce crosslinking between AgNWs upon ultraviolet (UV) irradiation. This crosslinking approach allows for the precise patterning of AgNWs. To further enhance the electrode characteristics of the AgNW network, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was selectively coated onto the AgNW patterns. The unique roughness-assisted wetting phenomenon facilitated the deposition of PEDOT:PSS, resulting in hybrid bilayer electrodes with low roughness, high oxidation resistance, and high mechanical stability. These AgNW/PEDOT:PSS hybrid transparent electrodes were used to create various electrochemical devices. Organic electrochemical transistors (OECTs) were employed as driver transistors, and they exhibited improved performance when using the hybrid electrodes compared to pristine AgNW network electrodes. This improvement was attributed to the low contact resistance and smooth surface of the hybrid electrodes.<br/> Furthermore, the AgNW/PEDOT:PSS hybrid electrodes were integrated into electrochromic (EC) devices, demonstrating their stability and suitability for applications involving charge transfer reactions. The devices exhibited reversible color changes and maintained their performance over numerous voltage cycles.<br/> Finally, a seven-segment active-matrix EC display was developed by integrating seven EC cells with their own driving OECTs. This display showcased the potential of the Ag NW/PEDOT:PSS hybrid electrodes for use in more complex optoelectronic devices.