Homogeneous dewetting on large-scale microdroplet arrays for solution-processed electronics

Unidirectional dewetting enables the production of large-area thin films with high efficiency at low cost. Herein, we report homogeneous unidirectional dewetting on large-area microdroplet arrays via gravity-induced deformation in droplets combined with alternating lyophilic/lyophobic patterns. This process allows the scaled-up deposition of thin films, including organic semiconductors and transition metal oxides, through the autogenous shrinkage of droplets, which further enables the fabrication of large-area organic thin-film transistor (OTFT) arrays. The resulting field-effect mobility and on/off ratio of the fully printed OTFTs exceeded 13 cm2 V−1 s−1 and 108, respectively. Therefore, the presented dewetting method is promising to realize the roll-to-roll manufacture of large-area flexible electronics. Large-scale arrays of microdroplets can be aligned into crystalline films for device purposes by tilting substrates perpendicularly. Dewetting freshly deposited liquid or solid films into small islands, similar to beads of water on glass, is an emerging technique for patterning organic semiconductor 'inks'. Takeo Minari from Japan's National Institute for Materials Science and colleagues have demonstrated the benefits of using gravity to induce ink dewetting in a single direction. Real-time imaging revealed that increasing the tilt angle caused the deformation of organic liquid microdroplets and the unidirectional dewetting, which resulted in unidirectionally-aligned large crystalline domains. The team exploited this behavior to solution print organic transistors with source and drain electrodes bridged by the single-crystalline semiconductor islands. The resulting flexible device had promising mobility and switching characteristics for roll-to-roll manufacturing. A Homogeneously unidirectional dewetting on large-area microdroplet arrays was developed, which was induced via the gravity-induced deformation in droplets combined with alternating lyophilic/lyophobic patterns. This process allows the scaling-up deposition of thin films including organic semiconductors and transition metal oxides as the autogenous shrinkage of droplets, which further enables the fabrication of large-area organic thin-film transistor (OTFT) arrays. The resulting field-effect mobility and on/off ratio of fully-printed OTFTs exceed 13 cm2 V−1 s−1 and 108, respectively.