Colloidal Liquid Crystalline Phases of Metal Halide Perovskites with Precisely Adjustable Band Gaps: Polarized Photoluminescence and Polarization-Dependent Photocurrents from Semiconductors with Self-Assembled Ordered Superstructures

Simultaneously possessing energy conversion properties and reconfigurable anisotropic structures due to their fluidity, semiconducting liquid crystals are an emerging class of soft materials for generating and detecting polarized photons. However, band-gap engineering of liquid crystalline substances remains challenging. Herein, semiconducting liquid crystals exhibiting discotic nematic ordering, linearly polarized monochromatic photoluminescence or broadband white-light emission, and polarization-dependent light-responsiveness (generation of photons and photocurrents) were systematically developed by transforming two-dimensional organic-inorganic metal halide perovskites into mesogenic colloidal nanoparticles. Emission wavelengths of the perovskite liquid crystals could be adjusted with an accuracy of 5 nanometers over a wide range in the visible region by compositional variations, indicating the possibility of fabricating polarized light-emitting or optoelectronic devices with desired band gaps using these materials.