Color brightness modulation of a responsive photonic liquid for multicolored electrochromic displays

Electrically-responsive photonic crystals have drawn extensive interest due to the growing demands of camouflage, displays, sensing, energy-saving buildings, etc., due to their fine control, fast response and convenient implementation. Veiled by the development on hue modulation, brightness/saturation tuning still remains a challenge. This work demonstrates a strategy to modulate the brightness of electrically-responsive photonic pixels via surface charge treatment of electrodes. The reflection intensity is raised by 110% due to the growth of the short-range ordered Fe3O4@C colloidal lattice as a result of enhanced Coulombic forces. The numerical simulation of the potential of the photonic liquid confirms that the potential distribution depends on the electrode surface charge. Furthermore, wide angle-independent photonic colors are well-tuned due to the anisotropic expansion/compression of the photonic lattice via electrophoretic movements of charged particles under an electric field. We believe that our work not only provides a useful way to modulate brightness but also suggests novel designs for electrically-responsive photonic devices.