Foldable Transparent Substrates with Embedded Electrodes for Flexible Electronics

Abstract

We present highly flexible transparent electrodes composed of silver nanowire (AgNW) networks and silica aerogels embedded into UV-curable adhesive photopolymers (APPs). Because the aerogels have an extremely high surface-to-volume ratio, the enhanced van der Waals forces of the aerogel surfaces result in more AgNWs being uniformly coated onto a release substrate and embedded into the APP when mixed with an AgNW solution at a fixed concentration. The uniform distribution of the embedded composite electrodes of AgNWs and aerogels was verified by the Joule heating test. The APP with the composite electrodes has a lower sheet resistance (Rs) and a better mechanical stability compared with APP without aerogels. The APP with the embedded electrodes is a freestanding flexible substrate and can be used as an electrode coating on a polymer substrate, such as polydimethylsiloxane and polyethylene terephthalate. On the basis of the bending test results, the APPs with composite electrodes were sufficiently flexible to withstand a 1 mm bending radius (rb) and could be foldable with a slight change in Rs. Organic light emitting diodes were successfully fabricated on the APP with the composite electrodes, indicating the strong potential of the proposed flexible TEs for application as highly flexible transparent conductive substrates.

Silver nanowire network embedded in polydimethylsiloxane as stretchable, transparent, and conductive substrates

“…In the absence of the aerogels, however, a nonuniform, sparse distribution of AgNWs was observed, as shown in the left FE-SEM image in Figure 2(b). Furthermore, the AFM surface image in the middle of Figure 2(b) shows traces of AgNWs that failed to be embedded, which corresponds to the valleys in the AFM line-scanning data in the right side of Figure 2 In our previous work, 13 we showed that aerogels could improve the transfer of AgNWs into a UV-curable polymer [Norland Optical Adhesive 68 (NOA 68)] because of the strong van der Waals interaction of the aerogels with the AgNWs and the matrix. The results in Figure 2(c) correspond well to those of our previous investigations.…”

“…In our previous work, we showed that aerogels could improve the transfer of AgNWs into a UV‐curable polymer [Norland Optical Adhesive 68 (NOA 68)] because of the strong van der Waals interaction of the aerogels with the AgNWs and the matrix. The results in Figure (c) correspond well to those of our previous investigations . Contrary to the results in Figure (b,c) shows uniformly embedded, dense AgNWs on the surface of the PDMS.…”

“…Given the extremely high surface‐to‐volume ratio of the aerogels, a strong van der Waals interaction is expected among the aerogels, AgNWs, and the PDMS when the aerogels are inserted between the AgNWs and PDMS. This strong interaction is expected to create denser AgNW networks embedded in the PDMS and to promote the detachment of the AgNWs from the release substrate during the embedding process …”

“…This strong interaction is expected to create denser AgNW networks embedded in the PDMS and to promote the detachment of the AgNWs from the release substrate during the embedding process. 9,13 The AgNWs were transferred into the PDMS with the aerogels; the highest sheet resistance (R s ) of the PDMS and the highest ratio between the R s and that of the AgNWs coated onto glass substrates (R s,0 ) (r t ) were 21.6 X/sq and 1.77, respectively. When the AgNWs on the glass are perfectly transferred to PDMS, r t is 1. r t becomes larger than 1 as less AgNWs is transferred into PDMS.…”

Emerging Novel Metal Electrodes for Photovoltaic Applications

“…Various polymer materials, such as PVA, PDMS, PMMA, polyimide, polyelectrolyte, poly(acrylate), etc., have been investigated for the fabrication of flexible transparent electrodes to meet specific requirements in practical applications. [164][165][166][167][168][169][170][171][172][173][174][175][176][177][178][179][180][181] Pei and coworkers have made a lot of contributions in this area and various polymer materials have been developed for the application of optoelectronic devices. [182][183][184][185][186][187][188][189][190][191][192][193]…”