Universal Low-Temperature Thermal Crosslinker for Photolithographic Lift-Off Ptterning of Solution-Processed Electronic Materials

Electronic materials containing moieties with good solubility to organic solvents (such as alkyl pendent groups in organic semiconductors or organic ligands on nanoparticles/nanocrystals) can exploited through cost-effective solution process in device manufacturing. However, the capability to solution-process these materials yields technical challenges in making patterns through photolithographic process available in industry, as the materials are likely to degrade during the process exposed to solvent (the solvent in photoresist or in developer). In this work, we propose photolithographic lift-off patterning applicable to various solution-processible materials (including light-emitting quantum dots, light-emitting polymer semiconductors, metallic nanoparticles) using a low-temperature crosslinker universally applicable to the materials without degrading the intrinsic electronic/optoelectronic properties. The crosslinker is designed to undergo direct crosslinking reaction with neighboring alkyl chains (included in the ligands on inorganic nanoparticles or the pendent chains in polymers) at an annealing temperature low enough not to degrade the chemical/structural properties of photoresist. Exploiting the chemical robustness of the resulting crosslinked film, we demonstrate that films of colloidal InP quantum dots, light-emitting Super Yellow polymers, or Au nanoparticles can be patterned at a few micro-meter scale through conventional photolithographic lift-off process. We believe that this approach paves a novel route to form micro-meter scale patterns of solution-processible materials without compromising electronic/optoelectronic properties.