Title : Circularly polarized electroluminescence from thin-film devices based on momentum-space engineering
일시 : 2022년 10월 11일(화), 17시
Speaker : 전영철(UNIST)
Abstract : Circularly polarized (CP) light sources are important for various applications including 3D displays, optical recording, optical communication, bioimaging, and biomedical diagnosis. Accordingly, CP light sources based on perovskite materials are attracting considerable attention to fully exploit their exceptional optoelectronic properties. Recently, there has been extensive research for achieving CP photoluminescence from perovskite materials (based on electronic Rashiba effect, chiral perovskites, etc). However, there was no demonstration of CP electroluminescence (EL) yet with a substantial degree of circular polarization (DCP), although it represents a critical step toward practical device applications.
In this talk, I present a recent experimental work from our group. We experimentally achieved CP EL with a substantial DCP (~0.38) using momentum-space engineering. Although various three-dimensional and two-dimensional chiral nanostructures have been studied and engineered in real space, strong chiral optical responses can also be obtained in momentum space. In our design, a periodic lattice of inversion-symmetry-broken polycrystalline silicon (poly-Si) patterns is integrated with an inorganic perovskite (CsPbBr3) EL device. The bottom poly-Si layer and top metal layer forms a photonic cavity; a Fabry–Perot resonance and guided resonance are spectrally overlapped, and their interactions can produce prominent CP EL with a large DCP in thin-film light-emitting devices. In our device, a pair of left circularly polarized (LCP) and right circularly polarized (RCP) EL is split into two opposite directions with equal power. Because many chiral applications require both LCP and RCP light sources, our design may be desirable for various applications requiring the compact CP light sources.