Slot‐Die Coated Organic UV Indicators and Filters Processed from Green Solvents

Abstract This work reports the use of the slot‐die (SD) coating solution processing method to fabricate large‐area organic thin films composed of photochromic dyes as UV indicators and UV light absorbers as UV filters on polyethylene terephthalate flexible substrates. This is the first demonstration of large‐area SD coated organic photochromic films and UV filters. Impressively, highly uniform photochromic films comprised of small molecules are formed in air, from green solvents (i.e., alcohols) and show rapid color changes upon external stimuli (i.e., light and heat). The UV filters processed under the same conditions and comprised of only small molecules show highly transparent films in the visible and near‐IR range with T% > 97%@550 nm and excellent UV blocking ability. The work highlights the utility of roll‐to‐roll compatible SD‐coating methods to make prototype organic devices in an academic laboratory setting and opens the door for additive manufacturing of simple and low‐cost UV active films for healthcare and electronic applications.