Herein, we report the enhancement in blue emission of nematic liquid crystals (NLCs) doped with CdSe quantum dots (QDs) at room temperature. CdSe QDs were synthesized by a high temperature wet chemical method. X-ray diffraction pattern suggest zinc blend crystal structure of CdSe QDs without impurity phase formation. The absorption peak and PL emission of QDs is observed at 503 nm and 526 nm respectively. The QDs size is found to be 2.3 nm calculated by excitonic peak. The polarization states of the QD-based NLCs were studied by using polarising optical microscopic (POM) images under crossed geometry of polarizer and analyser. The uniform colour distribution throughout the cell indicates uniform cell thickness with a planar alignment of liquid crystal molecules. Moreover, dark, and bright states of POM images are used to analyse the defects in alignment of NLC molecules. It is worthwhile to note here that the incorporation of QDs in NLCs helps in reducing defects and light leakage centres which further increases the absorption and hence emission of NLCs. The significant enhancement in the PL intensity of the NLC of about 60% upon CdSe QDs doping is observed at room temperature which attributed to the increase in molecular alignment of NLCs composite.

We report the enhancement in photoluminescence (PL) of nematic liquid crystals (NLCs) doped with CsPbBr3 (perovskite) quantum dots (QDs). QDs play a vital role to enhance the PL intensity, which has been attributed to the increase in the planar alignment of NLC molecules by reducing light leakage centres and intrinsic defects. QDs were synthesized by the hot injection chemical method. The structural properties of QDs were examined by X-ray Diffraction (XRD) and Transmission Electron Microscopic (TEM) measurements. Orthorhombic crystallite structure of CsPbBr3 QDs without secondary phase formation was confirmed from XRD pattern. The particle size of QDs was calculated by TEM and found to be 7.3 (± 1.1) nm. The optical properties of QDs were studied by recording UV-Visible absorption and PL spectra at room temperature. The absorption spectrum reveals the excitonic peak at 509 nm and PL emission is observed at 514 nm. The chemically prepared QDs were further used to enhance the emission of NLC. Firstly, liquid crystal sample cells were fabricated by conventional polyimide technique. NLC doped with CsPbBr3 QDs were inserted into the sample cell via the capillary action. The filled sample cells were characterized by polarising optical microscope (POM) images and PL spectra measurements. The dark and bright state images of POM demonstrate the uniform alignment and homogeneous texture of liquid crystal molecules in both cells. The molecular alignment is further improved while the light leakage centres and defects were reduced after doping QDs in the host NLC material. This leads to a significant enhancement in absorption and hence the emission of NLC. We found the enhancement in PL intensity by 11% compared to pure NLC. The improved emission of NLC is attributed to modified molecular alignment in presence of QDs. Results based on present work will help to fabricate QDs based display devices with improved the optical contrast and lower the operating voltage