Organic Indium Halides with Near-Unity Photoluminescence Quantum Yields for Highly Efficient Luminescent Inks and White Light Emitting Diodes

Zero-dimensional (0D) organic indium halides have been emerged as promising broadband light emitters with wide application prospects, but most of the present halides suffer from low photoluminescence quantum yield (PLQY), and a high-power excitation light source is needed to obtain desirable performance. In this work, we elaborately select appropriate organic cations as crystal structural engineering and obtained a series of highly efficient 0D indium bromides. Under UV light excitation, these 0D indium halides display broadband yellow light emissions (550-600 nm) with near-unity PLQYs, which represents one of the highest values in all the previously reported indium halides. Benefiting from successful nanoscale engineering, highly luminescent inks based on these 0D indium halides are facilely prepared by dispersing nanocrystals into various organic solvents. The luminescent ink can be utilized to print various anticounterfeiting patterns, which displays photoreversible switching with visible/invisible transformation under the alternating irradiation of UV and visible light. Furthermore, white light emitting diodes can be fabricated with high color rendering index above 90 by using these 0D halides as down-conversion phosphors. This work not only promotes the development of indium halides but also significantly broadens the application in solid-state illumination and anticounterfeiting, etc.