Organic-Inorganic Hybrid Nanowires as Multifunctional Photodetectors

DoctorOrganic-Inorganic hybrid materials have attracted great attention in scientific and industrial communities because they show the capability to take advantage of both inorganic and organic materials, while overcoming their own shortcomings. Recently, organic-inorganic hybrid nanowires (NWs) have emerged to develop multifunctional nanodevices such as NW logic device, ‘wavelength selective” NW photodetectors (PDs) and multi-spectral NWPDs. For development of NW-based multifunctional devices, it is required to precisely integrate single organic-inorganic hybrid NWs in the designed positions. However, it is still challenging to precisely integrate each NW addressing in the designed position despite recent efforts for development of integration methods such as flow-assisted alignment, Langmuir-Blodgett approach, and microcontact printing. In this study, I successfully realized the precise integration of organic-inorganic hybrid NWs by direct writing of organic-inorganic hybrid materials. This remarkable result was able to develop multifunctional PDs such as spectrum-discriminating NWPD array, high performance UV-visible-NIR NWPDs, and unprecedented stretchable NWPD array. First, I developed unprecedented single nanowires with ‘ambipolar (positive/negative) photoresponse’ that changes sign depending on illumination wavelength. Specifically, I show that single inorganic (ZnO nanoparticles)-organic (PEDOT:PSS) hybrid NWs integrated Au electrodes exhibit ambipolar (positive/negative) photoresponse photoresponse by illumination wavelength (UV/visible regime). I also demonstrated a “heart” pattern array of the single hybrid NWs, integrated at the planned sites, as spectrum (UV/visible)-discriminating photodetector array. Remarkably, the nanowires array shows a very small NW-to-NW photoresponse variation, indicating the excellent uniformity of integrated NWs. The single hybrid NWs with ambipolar photoresponse open an exciting opportunity for the creation of a spectrum-discriminating photodetector that can bridge UV photonics and visible photonics. Second, I developed high performance UV-visible-NIR NWPDs. Specifically, I for the first time achieved single PbS quantum dot (QD)-P3HT hybrid NWs by using meniscus-guided direct writing technology. The single PbS QD-P3HT hybrid NWPDs showed very high ON/OFF ratios in UV-visible range and very fast response time in UV range by two orders of magnitude comparing to previous results of NWPDs with UV to NIR response. The photoresponse of the hybrid NWPDs was significantly enhanced by controlling the concentration and size of QDs. This work suggests that our organic-inorganic hybrid NWs opens up possibility for high performance optoelectronic nanodevices Lastly, I demonstrated an unprecedented stretchable UV-visible-NIR NWPD array by individually integrating single PbS QD-P3HT hybrid NW arches on Au-Al electrodes embedded in PDMS. The NWPD array showed nearly identical photoresponse under extreme (up to 100%) and repeated stretching (up to 100 cycles), indicating excellent mechanical and photoelectrical stability. This demonstration will be an important step for stretchable/flexible nanophotonics in future. From this thesis, I suggest two major advancements in nanotechnology. First, this work describes the growth of organic-inorganic hybrid NWs, using the experimentally simple method, for high performance nanodevices with versatile functions. Second, this work introduces a novel integration technology for future stretchable nanophotonics based on the stretchable nature of NW arch structure presented in this work. I expect that direct writing of organic-inorganic hybrid NWs could be utilized for development of advanced optoelectronic and photonics nanodevices with unusual functionality