Cholesteric‐Superhelix‐Enabled Reconfigurable Circularly Polarized Luminescence from Uniaxially Aligned Upconversion Nanorod Films

The dissymmetry factor (|g(lum)|) in circularly polarized luminescence (CPL) shows great significance in many potential applications. The development of upconversion circularly polarized luminescence (UC-CPL) with a large dissymmetry factor is still limited by structural defects, especially in a self-assembly system. Here, a self-organized cholesteric liquid crystals (CLCs) composite is demonstrated, induced by uniaxially aligned upconversion nanorods (UCNRs) film, overcoming the aggregation issue via direct doping. The well-aligned UCNR film serves as a polarized emitter, and the cholesteric superhelixstructure enables the conversion from polarized upconversion luminescence (UCL) to a completely UC-CPL with an ultrahigh |g(lum)| value up to 1.92. Upon changing the concentration of chiral dopants or heating, the chiral UCL can be conveniently modulated via shifting the CLC reflection band to overlap with the UCL band. Moreover, UC-CPL with bidirectional asymmetric polarizations and emissions is achieved via forward and backward excitations. Furthermore, reversible switching from circular to linear polarization of UCL can be achieved by applying an electric field. Such a composite material system features versatile multimode and multiband modulation of UC-CPL with the significantly enhanced dissymmetry factor and multichannel modulation, providing new opportunities for advanced applications in photonics and biological optoelectronics.