Modulating the Surface via Polymer Brush for High‐Performance Inkjet‐Printed Organic Thin‐Film Transistors

Abstract

A strategy is reported to control the morphologies of inkjet‐printed small organic molecule semiconductor by modifying printed surfaces with polymer brushes. Polystyrene (PS) brushes with different chain lengths from 1.66 to 7.35 nm are grafted onto a dielectric surface via surface‐initiated atom transfer radical polymerization to form uniform, hydrophobic surfaces. Single droplets of 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐pentacene) are then inkjet‐printed onto these PS brush‐modified substrates. TIPS‐pentacene crystals are obtained with different morphologies depending on the chain length of the PS brushes. Short PS chains behave like self‐assembled monolayers on the dielectric surface such that small crystals are formed with random orientations. Longer PS chains become partially extended in the solvent altering ink spreading, contact‐line pinning, solute migration, and ultimately crystallization. Large self‐assembled crystals are generated with highly oriented structures. Organic thin film transistors are fabricated by printing single dots of TIPS‐pentacene. The device based on PS brushes of 5.14 nm exhibits the optimal device performances with an average mobility of 0.35 ± 0.23 cm2 V−1 s−1. These results demonstrate that these polymer brushes provide a route toward further understanding inkjet‐printing techniques for high‐performance organic electronics.