Abstract
Transparent electrode based on silver nanowires (AgNWs) emerges as an outstanding alternative of indium tin oxide film especially for flexible electronics. However, the conductivity of AgNWs transparent electrode is still dramatically limited by the contact resistance between nanowires at high transmittance. Polyvinylpyrrolidone (PVP) layer adsorbed on the nanowire surface acts as an electrically insulating barrier at wire–wire junctions, and some devastating post-treatment methods are proposed to reduce or eliminate PVP layer, which usually limit the application of the substrates susceptible to heat or pressure and burden the fabrication with high-cost, time-consuming, or inefficient processes. In this work, a simple and rapid pre-treatment washing method was proposed to reduce the thickness of PVP layer from 13.19 to 0.96 nm and improve the contact between wires. AgNW electrodes with sheet resistances of 15.6 and 204 Ω sq−1 have been achieved at transmittances of 90 and 97.5 %, respectively. This method avoided any post-treatments and popularized the application of high-performance AgNW transparent electrode on more substrates. The improved AgNWs were successfully employed in a capacitive pressure sensor with high transparency, sensitivity, and reproducibility.Electronic supplementary materialThe online version of this article (doi:10.1007/s40820-014-0018-0) contains supplementary material, which is available to authorized users.
Highlights
Transparent electrodes are regarded as essential components in optoelectronic applications such as solar cells, touch screens, organic light-emitting diodes, and sensor devices [1,2,3,4], and indium tin oxide (ITO) thin films are the Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users
During the synthesis and growth of AgNWs, the PVP capping agent was gradually adsorbed on the surface of the newly emerging silver crystals and grew with the crystals to be a nanolayer on the surface of the nanowire, formed from the merging of the crystals (Fig. 1c inset)
In this washing pre-treatment process, increasing the number of washing cycles leads to the gradual reduction in the thickness of PVP layer and the corresponding decrease in the sheet resistance especially at high transmittance
Summary
Transparent electrodes are regarded as essential components in optoelectronic applications such as solar cells, touch screens, organic light-emitting diodes, and sensor devices [1,2,3,4], and indium tin oxide (ITO) thin films are the Electronic supplementary material The online version of this article (doi:10.1007/s40820-014-0018-0) contains supplementary material, which is available to authorized users. bulk silver exhibits very low electrical resistivity, the conductivity of AgNW networks is limited, especially at high transmittance, by the contact resistance between wires due to the residual of polyvinylpyrrolidone (PVP) layer, which is usually employed as the capping agent to control nanostructure size and disperse nanowires during AgNW synthesis [12, 13]. (2015) 7(1): thermal annealing [14, 15], rinsing and pressure treatment [16], and photonic sintering [17] Other techniques such as nanosoldering, microwire enhancement, and galvanic displacement aim to remove the PVP layer or enlarge the contact area at wire–wire junctions [3, 18, 19]. All of these are the post-treatment methods after AgNWs are deposited on the substrate or the surface of device. Do these methods complicate the fabrication process, they inevitably influence the performance of the heat-sensitive, pressure-sensitive, or chemical-sensitive substrates
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