Creation of Nanotips on ITO Electrode by Nanoparticle Deposition: An Easy Way to Enhance the Performance of Electrically Responsive Photonic Crystal and Fabricate Electrically Triggered Anticounterfeiting Tags

Electrically responsive photonic crystals (ERPC) are promising materials for electrophoretic displays, smart windows, and tunable optical devices. However, the high working voltage limits the application of most polar ERPCs because it damages color saturation, response stability, and reversibility. Herein, an easy but general method based on the modification of electrodes with nanoparticles is developed to improve ERPC's performance. The deposition of Au, Cu, or Cu₂O nanoparticles created nanotip structures on the electrode, which enhanced the charge injection and local electric field strength, lowered 43% of the working voltage, and increased the color saturation. Meanwhile, the lowered voltage inhibited the electrodeposition of colloidal particles and the electrochemical reaction, which also improved the stability and reversibility of the electrical response. Based on the region-selective modification of the electrode and the resulting asymmetric electrical response, an electrically triggered tag with a “pattern showing/hiding” effect is fabricated for anticounterfeiting purposes.