Kyung Sun Park

High‐Performance Air‐Stable Single‐Crystal Organic Nanowires Based on a New Indolocarbazole Derivative for Field‐Effect Transistors

A new indolocabazole derivative possessing an extended aromatic core and solubilizing long aliphatic chains effectively self-assembles and crystallizes within the nanoscale channels to form single-crystal nanowires via a direct printing method from an ink solution. Single-crystal organic nanowire transistor arrays based on the π-extended indolocarbazole derivative exhibit an excellent hole mobility of 1.5 cm² V⁻¹ s⁻¹ and outstanding environmental stability.

Inkjet‐Assisted Nanotransfer Printing for Large‐Scale Integrated Nanopatterns of Various Single‐Crystal Organic Materials

Inkjet-assisted nanotransfer printing (inkjet-NTP) facilitates spatial control of many arrays of various organic functional materials on a single substrate with a high-throughput integration process, enabling monolithic integration of various organic nanopatterns. Inkjet-NTP enables wafer-scale organic electronic circuits composed of field-effect transistors, complementary inverters, and p-n diodes, demonstrating its capability to produce a high-performance, multifunctional organic chip.

Wafer-scale single-crystal perovskite patterned thin films based on geometrically-confined lateral crystal growth

We report a facile roll-printing method, geometrically confined lateral crystal growth, for the fabrication of large-scale, single-crystal CH3NH3PbI3 perovskite thin films. Geometrically confined lateral crystal growth is based on transfer of a perovskite ink solution via a patterned rolling mould to a heated substrate, where the solution crystallizes instantly with the immediate evaporation of the solvent. The striking feature of this method is that the instant crystallization of the feeding solution under geometrical confinement leads to the unidirectional lateral growth of single-crystal perovskites. Here, we fabricated single-crystal perovskites in the form of a patterned thin film (3 × 3 inch) with a high carrier mobility of 45.64 cm2 V−1 s−1. We also used these single-crystal perovskite thin films to construct solar cells with a lateral configuration. Their active-area power conversion efficiency shows a highest value of 4.83%, which exceeds the literature efficiency values of lateral perovskite solar cells.

Cross-Stacked Single-Crystal Organic Nanowire p−n Nanojunction Arrays by Nanotransfer Printing

We fabricated cross-stacked organic p-n nanojunction arrays made of single-crystal 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and fullerene (C60) nanowires as p-type and n-type semiconductors, respectively, by using a nanotransfer printing technique. Single-crystal C60 nanowires were synthesized inside nanoscale channels of a mold and directly transferred onto a desired position of a flexible substrate by a lubricant liquid layer. In the consecutive printing process, single-crystal TIPS-PEN nanowires were grown in the same way and then perpendicularly aligned and placed onto the C60 nanowire arrays, resulting in a cross-stacked single-crystal organic p-n nanojunction array. The cross-stacked single-crystal TIPS-PEN/C60 nanowire p-n nanojunction devices show rectifying behavior with on/off ratio of ∼ 13 as well as photodiode characteristic with photogain of ∼ 2 under a light intensity of 12.2 mW/cm(2). Our study provides a facile, solution-processed approach to fabricate a large-area array of organic crystal nanojunction devices in a desired arrangement for future nanoscale electronics.

Heterogeneous Monolithic Integration of Single-Crystal Organic Materials

Manufacturing high-performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high-performance organic electronic and optoelectronic devices relies on high-quality single crystals that show optimal intrinsic charge-transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high-performance organic integrated electronics are also addressed.

One-step fabrication of nanowire-grid polarizers using liquid-bridge-mediated nanotransfer molding

Ag nanowire-grid polarizers (NWGPs) were prepared by a one-step fabrication method, called liquid-bridge-mediated nanotransfer molding (LB-nTM). LB-nTM is a new direct nano-patterning method based on the direct transfer of various materials from a mold to a substrate via liquid layer. We fabricated NWGPs with Ag nanowire arrays (81 nm parallel lines and 119 nm spaces) on 2.5 in. transparent substrates by LB-nTM using an Ag nanoparticle solution. The maximum and minimum transmittances of the Ag NWGP at 800 nm were 80% and 10%, respectively.

Observation of Charge Separation and Space-Charge Region in Single-Crystal P3HT/C60 Heterojunction Nanowires.

We directly observed charge separation and a space-charge region in an organic single-crystal p-n heterojunction nanowire, by means of scanning photocurrent microscopy. The axial p-n heterojunction nanowire had a well-defined planar junction, consisted of P3HT (p-type) and C60 (n-type) single crystals and was fabricated by means of the recently developed inkjet-assisted nanotransfer printing technique. The depletion region formed at the p-n junction was directly observed by exploring the spatial distribution of photogenerated carriers along the heterojunction nanowire under various applied bias voltages. Our study provides a facile approach toward the precise characterization of charge transport in organic heterojunction systems as well as the design of efficient nanoscale organic optoelectronic devices.

Ultra Gas-Proof Polymer Hybrid Thin Layer

Hermetic sealing is an important technology for isolating and protecting air-sensitive materials and is key in the development of foldable and stretchable electronic devices. Here we report an ultra gas-proof polymer hybrid thin layer prepared by filling the free volume of the polymer with Al2O3 using gas-phase atomic layer infiltration. The high-density polymer-inorganic hybrid shows extremely low gas transmission rate, below the detection limit of the Ca corrosion test (water vapor transmission rate <10-7 g m-2 day-1). Furthermore, because of the remarkable nanometer-scale thinness of the complete polymer-inorganic hybrid, it is highly flexible, which makes it useful for hermetic sealing of stretchable and foldable devices.

Nanotransfer Printing: Inkjet-Assisted Nanotransfer Printing for Large-Scale Integrated Nanopatterns of Various Single-Crystal Organic Materials (Adv. Mater. 15/2016).

Inkjet-assisted nanotransfer printing, described by M. M. Sung and co-workers on page 2874, enables monolithic integration of crystalline nanowire arrays with a diverse range of organic materials. Droplets of different molecular ink solutions are transformed into single-crystal organic nanowires within nanoscale channels at selected locations in a nanoscale line-patterned mold. Patterned arrays of various functional nanowires within the mold are then printed directly onto a substrate through the liquid-bridge-mediated transfer process.