# Stability of Silver-Nanowire-Based Flexible Transparent Electrodes under Mechanical Stress
## 1 Introduction  
Electronic components have evolved from heavy and rigid into lightweight and flexible structures, thereby allowing us the flexibility to use various devices anytime, anywhere [1; 2; 3]. Specifically, traditional transistors are heavy and inflexible, but recently reported transistors have been manufactured in lightweight and flexible forms capable of bending and stretching [4; 5; 6]. Similarly, solar cells, which were traditionally manufactured using rigid inorganic materials, now have lightweight and portable device architectures [7; 8; 9; 10]. One of the strategies that can provide such flexibility and lightness to various optoelectronic components is the adoption of flexible transparent electrodes [11; 12]. Flexible transparent electrodes have been developed based on organic and nanomaterials, which has made heavy and unbendable substrates redundant [13; 14; 15].  
Early flexible transparent electrodes were fabricated by depositing indium tin oxide (ITO) onto polyethylene terephthalate (PET) films [16; 17; 18]. The ITO deposition techniques are highly mature and therefore offer the advantage of ease of production [19; 20]. However,ITO, a ceramic material based on inorganic elements, generates cracks when subjected to external stress, resulting in an increase in the resistance of transparent electrodes and limiting the service life of flexible electronic components [21; 22; 23]. Various materials have been developed to overcome these challenges. Silver nanowires (AgNWs) are one of the promising materials for producing flexible electrodes with long-term stability [24; 25; 26]. People have reported various applications of AgNW-based electrodes, including solar cells, organic light-emitting displays, and sensors [27; 28; 29]. Flexible electrodes based on AgNWs are manufactured by simply coating AgNWs on a PET substrate or by coating AgNWs on a substrate with weak adhesion, pouring the polymer on top, curing it, and then peeling it off to create a AgNW-embedded form in the polymer [30; 31]. They have been demonstrated to be applicable in various optoelectronic devices such as solar cells and organic light-emitting devices [32; 33; 34]. However, how various types of AgNW-based electrodes exhibit different behaviors and how their physical properties change depending on the type of external stress have not yet been investigated.  
In this study, we investigated the changes in the electrical, morphological, and optical characteristics of AgNW-exposed and AgNW-embedded electrodes under compressive and tensile stress. For the fabrication of AgNW-exposed electrodes, PET was used as the substrate, and NOA63 and NOA71 were used for the AgNW-embedding process. The sheet resistance was measured to evaluate the electrical properties. The morphological properties were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Further, ultraviolet-visible (UV-Vis) spectroscopy measurements were conducted to evaluate the optical properties. Through a comprehensive analysis of these characteristics, we determined which electrode configuration performs optimally as a flexible transparent electrode under compressive and tensile stresses.