Direct Photolithography of Perovskite Nanocrytstals via i-Line Ligand Crosslinking

Perovskite nanocrystals (PeNCs) are promising materials for electroluminescence (EL) applications in display due to their high quantum yield, narrow emission line as well as low-cost, simple synthesis method. In fabricating EL devices, patterning of PeNCs is a crucial step that determines the resolution and color purity. While conventional photolithography using photoresist is the seemingly adequate patterning process to meet the industrial requirement, the polar solvents commonly used for processing the photoresist is detrimental to PeNCs with strong ionic characteristics. Herein, we demonstrate photoresist-free, direct photolithography of CsPbX₃ PeNCs using an <i>i</i>-line (365 nm) UV source. This is specifically achieved with aids of light-induced ligand crosslinker (LiXer) that forms chemical bonding with the ligands of neighboring PeNCs to interlock them. Because <i>i</i>-line UV was exploited, the photoluminescence (PL) characteristics of PeNCs could be fully preserved upon irradiation, which was not the case when using 254 nm-DUV source. The use of benign <i>i</i>-line UV source is critical not only that it permits patterning PeNCs non-destructively but also because the apparatus is most widely available in display industry.