Aligned silver nanowire-based transparent electrodes for engineering polarisation-selective optoelectronics.

Byoungchoo Park,In-Gon Bae,Yoon Ho Huh

doi:10.1038/srep19485

Abstract

We herein report on a remarkably simple, fast, and economic way of fabricating homogeneous and well oriented silver nanowires (AgNWs) that exhibit strong in-plane electrical and optical anisotropies. Using a small quantity of AgNW suspension, the horizontal-dip (H-dip) coating method was applied, in which highly oriented AgNWs were deposited unidirectionally along the direction of coating over centimetre-scale lengths very rapidly. In applying the H-dip-coating method, we adjusted the shear strain rate of the capillary flow in the Landau-Levich meniscus of the AgNW suspension, which induced a high degree of uniaxial orientational ordering (0.37–0.43) of the AgNWs, comparable with the ordering seen in archetypal nematic liquid crystal (LC) materials. These AgNWs could be used to fabricate not only transparent electrodes, but also LC-alignment electrodes for LC devices and/or polarising electrodes for organic photovoltaic devices, having the potential to revolutionise the architectures of a number of polarisation-selective opto-electronic devices for use in printed/organic electronics.

Highlights

To fabricate AgNW films on solid substrates we used AgNWs suspended in isopropyl alcohol (IPA) (0.5–2.0 wt%) (NTC-01, Nanopyxis Co., LTD.), with an average diameter and length of about 25 nm and 32 μ m, respectively
The surface morphology results obtained by AFM show that the values of the rms surface roughness for 40, 60, and 200 nm-thick H-dip-coated AgNWs were 12.8, 18.4, and 26.0 nm, respectively, which were almost identical at different positions on the investigated layers, while the rms surface roughness observed for the 40-nm-thick spin-coated AgNWs was ~22.1 nm
We investigated the optical microscopic properties of the AgNWs under a polariser: the observed texture is bright-state when the x-direction of the AgNWs is perpendicular to the transmission axis (P) of the polariser, but becomes dark-state when the x-direction is parallel to the P axis, indicating the clear dichroic properties of the AgNWs

Summary

Results and Discussion

In contrast to the isotropic absorptions of the PCDTBT:PCBM70 PV layer (Fig. 4a) and the spin-coated AgNW electrode (Supplementary Fig. S1b), the sample AgNW-OPV cell with the H-dip-coated AgNW anode shows clear absorption anisotropy due to the oriented. When tested under unpolarised glass illumination, the sample AgNW-OPV cell with the 85 nm-thick PCDTBT:PCBM70 PV layer and the H-dip-coated AgNW anode achieved a power conversion efficiency (PCE) of 2.22%, with a short-circuit current density (JSC) of 9.35 mA/cm[2], an open-circuit voltage (VOC) of 0.82 V, and a fill factor (FF) of 29.08%, while when tested under unpolarised Ag-illumination, the cell showed a PCE of 1.99%, with a JSC of 8.13 mA/cm[2], a VOC of 0.82 V, and an FF of 29.85% (Supplementary Table S1 and Fig. S5). Considering all these results, it is clear that oriented AgNWs produced by H-dip-coating can act as a multi-functional anisotropic optical and electrical component in various polarising opto-electronic devices

Conclusions

Author Contributions

Additional Information