High color saturation and angle-insensitive ultrathin color filter based on effective medium theory

An ultrathin angle-insensitive color filter enabling high color saturation and a wide color gamut is proposed by relying on a magnesium hydride-hydrogenated amorphous silicon (MgH2-a-Si:H) lossy dielectric layer. Based on effective medium theory, the MgH2-a-Si:H layer with an ultrathin thickness can be equivalent to a quasi-homogeneous dielectric layer with an effective complex refractive index, which can be tuned by altering the thickness of MgH2 to obtain the targeted value of the imaginary part, corresponding to the realization of high color saturation. It is verified that the proposed color filter offers highly enhanced color saturation in conjunction with a wide color gamut by introducing a few-nanometer thick MgH2 layer. As the MgH2-a-Si:H layer retains the advantages of high refractive index and tiny thickness, the proposed color filter exhibits large angular tolerance up to ±60°. In addition, MgH2 with an unstable property can interconvert with Mg under a dehydrogenation/hydrogenation reaction, which empowers the proposed color filter with dynamically tunable output color. The proposed scheme shows great promise in color printing and ultracompact display devices with high color saturation, wide gamut, large angular tolerance, and dynamic tunability.