Highly Efficient and Ultrafast Terahertz Modulation in Perovskite Hybrid Structure

A terahertz optical modulator based on CH3NH3PbI3/Ag wire grid/graphene was studied. The Ag wire grid structure effectively enhanced the modulation of the CH3NH3PbI3/graphene hybrid structure for terahertz waves. The wire grid served as a transfer channel for the photo-induced electrons generated in the perovskite layer, which realized the separation of photo-generated electrons and holes, reducing the probability of recombination and forming effective charge collection in the graphene layer. The modulation depth of the CH3NH3PbI3/Ag wire grid/graphene to the terahertz beam was 2.3 times that of the nonwire grid structure. The transient THz transmission upon 800 nm optical pump showed an initial positive transmission (negative THz photoconductivity), followed by a negative THz transmission (positive THz photoconductivity), which presented a strong time-dependence. Experimental results demonstrated that the developed device may also provide a possible application for the detection of visible light.