Recent advances and future perspectives of photoluminescent liquid crystals and their nanocomposites for emissive displays and other tunable photonic devices

Liquid crystal (LC) materials have been playing a significant role in the field of displays and other photonic devices. For instance, they are being continuously utilized in a wide range of optoelectronic devices from sensors, lasers, tunable filters/gratings/lenses, wrist watch, pocket calculator, automobile's meter to ultrahigh definition flat liquid crystal display (LCD) panels. However, LCDs require a fluorescent lamp (or light emitting diode) for backlighting due to their non-emissive (or weak emissive) capability. The use of colour filters in LCDs also put a limit on the brightness of LCDs. Interestingly, some of the organic LC materials with inherent emission may offer less dependence of LCDs on the backlighting and color filters. To boost the inherent emission of LCs upto the level which excludes the requirement of color filters, highly emissive nanomaterials (NMs, metal/metal oxides, semiconducting and carbon) may be utilized to enhance the photoluminescence (PL) intensity of NMs-LCs nanocomposites. In the present article, we review reports on PL of pure LCs as well as enhanced and tunable PL of NMs-LCs nanocomposites. Moreover, the future perspectives of such photoluminescent LCs and their composites with nanomaterials is discussed.