투명 유연 나노 전자소자를 위한 무기 금속 산화물/유기물 나노와이어

Abstract

Future ubiquitous optoelectronics require versatile features, such as the portability, wearability, transparency and flexibility with a superior electrical and mechanical stability. The technological innovations, research, and the fabrication processes of the next-generation optoelectronics have propelled the flexible and transparent display industry to greater heights. Transparent and flexible transistors for circuits and systems represent a key research area for future applications for invisible electronics. In particular, one dimensional nanostructure such as a nanowire is desirable attribute that offer higher mobility, transparency and flexibility for the transparent and flexible transistors. Nanowires required for optoelectronic researches are classified according to the electrical conductivity of the materials, such as semiconducting and conducting materials. Two kinds of nanowires are positively necessary components to compose the flexible and transparent nano-electronics. During the last decades, various methods were developed consequently for nanowires mass production, but they usually suffer from the difficulty in precise control position and orientation of individual nanowires. A novel approach is required to overcome limitations, we develop the direct printing system, electrohydrodynamic nanowire printer (e-NW printer). The e-NW printing method, which employs a strong electrical field to elongate polymers from a viscous solution into solid-state wires, is probably so far the most powerful and most popular technique to produce long, continuous and aligned nanowire. A key challenge for nano-electronics is the designable alignment of one-dimensional nanostructures. In Chapter 3, we introduce a e-NW printing method that prints arbitrarily long and continuous precursor-incorporated micro and nanowires (NWs) on a large area with computer-digital-control to achieve designed metal oxide micro and nanowire (MOW) patterns. Scalable fabrication of various long continuous MOWs that were digitally aligned on a large area was successfully achieved, indicative of broad applicability of the technique. The MOWs were then utilized for the fabrication of field-effect transistors (FETs) to demonstrate their versatile electronic applications. We fabricated unprecedented large-scale all-wire transistors using semiconducting IZO NWs and conducting In2O3 NWs with a high mobility of ~17.67 cm2/Vs, which provide a useful platform for fully transparent electronics. This is a benefit of longitudinal crystal structure along the channel. The e-NW printing is a simple, inexpensive, and rapid fabrication approach that can solve the difficulties in aligning MOWs, and thus provides an important addition to the state-of-art technologies towards future nano-electronics and transparent electronics. In Chapter 4, flexible organic-nanowire transistors are fabricated using e-NW printed highly-aligned polymer nanowires as semiconducting channels and self-patterned PFI-doped PEDOT:PSS conducting polymer electrodes. All polymer transistors were also successfully obtained. The devices exhibited significantly enhanced charge carrier mobility and endure extreme bending tests. These superior electrical properties of the devices pave the way to realization of future flexible nano-electronics. In Chapter 5, organic and inorganic hybrid nanowire p-n junction photodiodes are fabricated using highly-aligned polymer (P3HT:PEO blended p-type NW) and metal oxide (ZnO, IZO, IGZO, n-type NW) nanowires as semiconducting channels printed e-NW printing method. Both polymer and metal oxide nanowires successfully formed the cross-stacked nanoscale p-n junction for the enhanced sensing performance. The nanowires nano-junction exhibited good rectification ability as well as photodiode characteristics. Our study demonstrated that organic and inorganic hybrid nanowire photodetector is beneficial in the advancement of novel nano-scale photo-responsible technology.