No abstract

Semiconductor nanorods (NRs) with strong fluorescence anisotropy are considered promising polarized light sources for liquid crystal displays. Here, we achieved a high fluorescence anisotropy value of 0.4 in the mixed-anion lead halide perovskite NRs, which constitutes a four-fold enhancement as compared to pristine CsPbBr 3 NRs. This was realized by substituting some smaller bromine anions with larger iodine anions in the orthorhombic CsPbBr 3 NRs via anion exchange. The resulting CsPbBr 1.2 I 1.8 NRs kept a highly uniform length of ∼36 nm and width of ∼8.6 nm, and possessed a high emission quantum yield of 83%. On the basis of the DFT calculations, we attribute the improved polarized emission of the mixed-anion perovskite NRs to a moderate structural distortion of PbX 6 octahedra units in the orthorhombic perovskite lattice, which results in a preferred direction of the optical transition dipole moment along the Pb−X−Pb axis. Our study provides a guidance for design and fabrication of perovskite NRs with high fluorescence anisotropy.

Inkjet printing of quantum rods on to the photoaligned substrate opens up the possibility of both brightness and color enhancement for liquid crystal displays (LCD) in the form of quantum rod enhancement films (QREF) for LCD backlights.

The photoalignment process to align semiconductor quantum rods (QRs) in the liquid crystal monomer (LCM) matrix is a flexible technology; however, the optical quality of the resulting enhancement films drops at high concentrations of the QRs. The compatibility between the ligand shell on the QRs and the LCM plays an important role in avoiding this issue. Herein, several kinds of ligand shells on the rod-in-rod CdSe/CdS QRs are designed, without affecting the optical properties of QRs, and their compatibility with LCM molecules is studied. Promesogenic dendritic ligands in combination with relatively short alkylphosphonic acids are found to provide the highest optical quality, without QR aggregation, and so the high brightness of the resulting enhancement films, even at higher concentrations of QRs in LCM, which is perfectly suitable for the application in liquid crystal displays.