Solution processed all-carbon transistors via directed assembly and transfer printing of CNT channel and electrodes

Carbon nanotube (CNT) field effect transistors (FETs) have shown great promise for flexible device applications, but a method to selectively print each layer with high fidelity and low cost on flexible substrates remains elusive. To address this gap, we combine the simplicity of directed assembly with the high resolution and pattern fidelity of transfer printing to print all-carbon transistors on a flexible polyimide substrate. For the presented device, the channel and electrodes consist of semiconducting single-walled CNTs and multi-walled CNTs, respectively. We demonstrate an approach to selectively assemble multi-walled CNTs on a chemically heterogenous surface of a highly doped silicon wafer using electrophoresis, while single-walled CNTs are assembled on a photoresist templated substrate using meniscus driven fluidic assembly. Both layers are sequentially transfer printed on a stack of polyurethane and SU-8, which serves as the gate dielectric. This approach utilizes lithographically patterned silicon wafers as reusable templates, which significantly lowers the manufacturing cost and provides greater resolution than other printing techniques. The printed transistors exhibit on/off ratio as high as 106 with mobility approaching 10 cm2 V−1 s−1, which is highly promising for fully printed flexible FETs.