Solution-processed, high-performance n-channel organic microwire transistors

Abstract

The development of solution-processable, high-performance nchannel organic semiconductors is crucial to realizing low-cost, all-organic complementary circuits. Single-crystalline organic semiconductor nano/microwires (NWs/MWs) have great potential as active materials in solution-formed high-performance transistors. However, the technology to integrate these elements into functional networks with controlled alignment and density lags far behind their inorganic counterparts. Here, we report a solutionprocessing approach to achieve high-performance air-stable nchannel organic transistors (the field-effect mobility ( ) up to 0.24 cm 2 /Vs for MW networks) comprising high mobility, solutionsynthesized single-crystalline organic semiconducting MWs ( as high as 1.4 cm 2 /Vs for individual MWs) and a filtration-and-transfer (FAT) alignment method. The FAT method enables facile control over both alignment and density of MWs. Our approach presents a route toward solution-processed, high-performance organic transistors and could be used for directed assembly of various functional organic and inorganic NWs/MWs. organic semiconductors ͉ single crystals ͉ solution processing ͉ alignment S olution-processable, high-performance n-channel (electrontransporting) organic semiconductors are indispensable for cost-effective production of all-organic, flexible complementary logic elements (1-3). To date, however, very few solutionprocessable, air-stable organic n-channel semiconductors matching the performance of amorphous silicon (a-Si) ( Ն 0.1 cm 2 /Vs) have been reported (4-8). Organic semiconductor nano/microwires (NWs/MWs) have recently emerged as promising building blocks for various electronic and optical applications such as light-emitting diodes (LEDs) (9), field-effect transistors (FETs) (10), photoswitches (11), vapor sensors (12), solar cells (13), nanoscale lasers (14), optical waveguides (15), and memory devices (16). These unique materials combine the high-performance of singlecrystalline structures with solution-processability by dispersion (17,18). Several p-channel (hole-transporting) organic wires prepared by solution-processing have exhibited Ͼ 0.1 cm 2 /Vs for singlewire transistors (19)(20)(21)(22), whereas only a few solution-synthesized n-channel organic wires have been reported, typically with low performance ( Ϸ10 Ϫ3 Ϫ 10 Ϫ2 cm 2 /Vs) (23,24).Despite the intrinsic high mobility of single-crystalline wires, precise wire placement and wire-to-wire performance variation, due to the difference in the contact quality at the wire/insulator and wire/electrode interfaces, substantially hinder successful device integration (10, 25). Therefore, the technology to achieve network films of organic MWs deposited from a dispersion with controlled alignment and density is acutely desired. The integration of inorganic and metallic wires into functional network films has been extensively explored by using a number of methods such as the flow cell method (26), electric field (27, 28), magnetic field (29), electrospinning (30),...

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