# Improvement of Electro-Optical Properties of PSLC Devices by Silver Nanowire Doping
## 3 Results and Discussion  
### Effect of Ag Nanowires on the Driving Voltage of PSLC Devices  
The voltage-transmittance (V-T) curves, threshold voltages and leakage current of the Ag nanowire doped PSLC according to the Ag nanowire concentration are shown in Figure 5. The V-T curve of PSLC devices under 1 kHz square wave AC driving are shown in Figure 5a. All PSLC devices have transmittance above 95% at off state and the transmittance decreases as the voltage increases. All devices can reach a scattering state with transmittance under 18%. However, the transmittance at both on and off state decreased slightly with small amount of Ag nanowire doping at 0.01 wt.%, and the transmittance increased as the Ag nanowire concentration was increased up to 0.1 wt.%. This is because, when the concentration is too high, Ag nanowires cannot be evenly distributed in the LC and tend to aggregate together, resulting in the interconnection between the silver nanowires [34]. When the voltage continuously increased, aggregation of silver nanowires will form a local short circuit and burn up the device, thus affecting the device performance and increasing the transmittance of the device. Meanwhile, the V-T curve of the PSLC had a different tendency: the threshold voltages (V\({}_{10}\) and V\({}_{90}\)) shifted as a function of the Ag nanowire concentration. It shifted to the left side first as the Ag nanowire concentration increased to 0.02 wt.%, and then shifted to the right side as the Ag nanowire concentration continued to increase. The V-T curve of PSLC devices doped with 0.01 wt.%, 0.02 wt.%, and 0.05 wt.% Ag nanowires are on the left side of the undoped PSLC device. However, the V-T curve of PSLC device doped with 0.1 wt.% Ag nanowires is on the right side of the undoped PSLC device, meaning it has worse performance than the undoped PSLC device. The voltages for 10% transmission (V\({}_{10}\)) and 90% transmission (V\({}_{90}\)) show the same tendency. As shown in Figure 5b, V\({}_{10}\) and V\({}_{90}\) greatly decreased with a small amount of doping at 0.01 wt.% Ag nanowires, and the values decreased as the Ag nanowire concentration was increased up to 0.02 wt.%. However, the V\({}_{10}\) and V\({}_{90}\) values started increasing when the Ag nanowire concentration continued increasing up to 0.1 wt.%. When the doping concentration is 0.02 wt.%, the threshold voltage is lowest, reduced by 35-42% compared with undoped PSLC device. The reduction of the residual DC voltage through metal nanomaterial doping in the nematic LC is discussed in the literature [35; 36]. Metal nanomaterials mixed in LC materials can capture ionic impurities and enhance the electro-optic properties of LCs. Due to the small size effect of the silver nanowire, when a voltage is applied, the surface of the silver nanowire will be polarized, and thus the ionic impurities in the liquid crystal mixture will be absorbed by the silver nanowire surface. Therefore, the reason that doping a certain concentration of Ag nanowires can reduce the threshold voltage of  
Figure 4: Experiment setup for transmittance and response time measurement (when measuring response time, the integrating sphere was replaced with a photodiode, while the spectrometer was replaced by amplifier and acquisition card). the PSLC device is Ag nanowire doping can effectively eliminate the ionic impurities in the LC and reduce the conductivity in the PSLC device. Figure 5c shows the current-voltage curves of PSLC devices doped with different concentrations of Ag nanowires. At a certain voltage, the current of PSLC devices doped with 0.01 wt.% and 0.02 wt.% Ag nanowires decreasing when the concentration of Ag nanowire increases. When the Ag nanowire doping concentration is 0.02 wt.%, the current is the lowest, which represents the lowest conductivity. This is because the ionic impurities in the PSLC mixture is captured by the Ag nanowires. When the conductivity of LC material is the lowest, the electric field and force applied on the liquid crystal molecule is the strongest.