Effective Molecular Alignment of Semiconducting Polymer and Its Application to Photopatterned Stretchable Transistors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-05 |
| Journal | Advanced Materials Technologies |
| Authors | Yasutaka Kuzumoto, SungâGyu Kang, Hyunbum Kang, Sangah Gam, Hyungjun Kim |
| Institutions | Hallym University, Samsung (South Korea) |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the development of high-mobility, fine-patterned, intrinsically stretchable organic thin-film transistors (int-OTFTs) using a novel fabrication approach combining material alignment and interface engineering.
- High Mobility Achieved: The optimized process yielded a peak mobility of 3.17 cm2 V-1 s-1 on rigid substrates, which is 3.6 times higher than conventional spin-coating methods and exceeds the performance of amorphous silicon.
- Enhanced Molecular Alignment: High mobility was achieved by combining solution shearing with nano-grooved substrates (G-s), significantly improving the crystalline structure and facilitating strong Ï-Ï stacking of the DPP-P/SEBS semiconductor blend.
- High-Performance Stretchable Device: Photopatterned int-OTFTs with a short channel length (10 ”m) demonstrated excellent performance metrics: 2.66 cm2 V-1 s-1 mobility and an ultra-low off-current of 0.96 pA.
- Interface Engineering: A 1-bromooctane (1-BO) solvent treatment was applied to the stretchable micro-cracked Au electrodes, effectively reducing the contact resistance (RonW) from 5.1 MΩ cm to 790 kΩ cm.
- Robust Stretchability and Durability: The int-OTFTs maintained stable electrical properties with only minor variations under 50% applied strain and demonstrated high durability after 1000 stretching cycles at 40% strain.
- Material System: The stretchable semiconductor composite consists of a diketopyrrolopyrrole-based polymer (DPP-P) and a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene elastomer (SEBS).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Peak Mobility (Solution Sheared, G-s) | 3.17 ± 0.21 | cm2 V-1 s-1 | Rigid substrate, parallel to grooves |
| Peak Mobility (Photopatterned int-OTFT) | 2.66 | cm2 V-1 s-1 | W/L = 100/10 ”m, intrinsically stretchable |
| Off-Current (Ioff) | 0.96 | pA | Photopatterned int-OTFT, L = 10 ”m |
| Mobility Ratio (Anisotropy) | 5.54 | N/A | H1221-s-OSC, parallel/perpendicular mobility ratio |
| Contact Resistance (RonW) | 790 | kΩ cm | With 1-BO treatment (VDS = -0.5 V, VGS-Vth = -3 V) |
| Gate Insulator Capacitance | 3.9 | nF cm-2 | Cross-linked SEBS |
| Maximum Strain Tested | 50 | % | Stable electrical properties |
| Cycling Durability | 1000 | Cycles | Tested at 40% strain |
| Nanogroove Lapping Film | 0.1 | ”m | Diamond particle size |
| Shearing Speed Range | 2-4 | mm s-1 | Solution shearing process |
| Shearing Substrate Temperature | 70 | °C | During s-OSC coating |
| Annealing Temperature | 190 | °C | Post-coating annealing (1 hour) |
| DPP-P:SEBS Weight Ratio (Shearing) | 3:7 | N/A | Optimized for solution shearing |
| DPP-P:SEBS Weight Ratio (Spin-coating) | 6:4 | N/A | Optimized for spin-coating |
| Lamellar Stacking Distance | 2.5 | nm | Determined by GIWAXS (qz = 0.25 A-1) |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication of the high-performance, photopatterned int-OTFTs involved several critical steps focused on molecular alignment and interface control:
- Nanogrooved Substrate Preparation (G-s): Rigid substrates (SiO2/Si or glass) were rubbed 50-100 times using a 0.1 ”m diamond lapping film (pressure â 0.1 kg cm-2) to create nano-grooves. These surfaces were subsequently modified with an ODTMS self-assembled monolayer (SAM).
- Stretchable Substrate and Electrode Fabrication: A dextran sacrificial layer was coated on glass, followed by a highly cross-linked SEBS layer (substrate/gate insulator). Micro-cracked Au electrodes (gate, source, and drain) were patterned using thermal deposition and lift-off.
- Interface Treatment: The surface of the S/D electrodes and gate insulator was treated with 1-bromooctane (1-BO) solvent (spin-coated five times) to remove surface impurities (photoresist residue, PFBT) and significantly reduce contact resistance prior to semiconductor transfer.
- Molecular Alignment via Solution Shearing: The DPP-P/SEBS solution (3:7 ratio) was coated onto a rigid G-s substrate using a solution-shearing technique, aligning the polymer chains parallel to the nano-grooves and the intended channel direction.
- s-OSC Transfer: The aligned s-OSC film was transferred from the rigid G-s substrate onto the stretchable BG-BC structure using a PDMS film, ensuring the nanogroove/shearing direction was parallel to the channel length.
- Photopatterning of s-OSC: The transferred s-OSC layer was photopatterned using a fluorinated photoresist and dry etching to define the active channel area and suppress parasitic current leakage.
- Encapsulation and Release: The device was encapsulated with a SEBS layer. The sacrificial dextran layer was dissolved in water, releasing the fully stretchable int-OTFT film from the rigid glass substrate.
Commercial Applications
Section titled âCommercial ApplicationsâThe development of high-mobility, intrinsically stretchable organic transistors is critical for next-generation flexible and wearable electronics.
- Stretchable Displays: Enabling high-resolution, durable backplanes for displays that can conform to complex, dynamic surfaces (e.g., automotive interiors, clothing).
- Skin-Like Electronics: Fabrication of highly compliant, skin-mounted sensors, health monitors, and human-machine interfaces requiring high mobility and mechanical robustness.
- Smart Textiles and Wearables: Integration of complex electronic circuits directly into clothing or flexible devices that must withstand significant stretching and cycling.
- Flexible Integrated Circuits: Use in stretchable logic circuits and memory arrays where performance must exceed that of typical amorphous silicon or low-mobility organic materials.
- Advanced Sensing: Creation of large-area, stretchable sensor arrays (e.g., pressure, temperature) that require high signal processing speed provided by high-mobility TFTs.
View Original Abstract
Abstract Intrinsically stretchable organic transistors are promising solutions for realizing stretchable electronic systems, such as skinâlike wearables and nextâgeneration displays. Nevertheless, applying stretchable organic thinâfilm transistors to highâend display backplanes requires enhancing key electrical properties, including mobility and offâcurrent, beyond the amorphous Si level, particularly for short channel lengths. Herein, enhanced performances of intrinsically stretchable organic transistors with a high degree of molecular alignment in stretchable semiconductor composites, comprising a diketopyrrolopyrroleâbased polymer and polystyreneâblockâpoly(ethyleneâranâbutylene)âblockâpolystyreneâelastomer, utilizing the solution shearing process on nanogrooved surfaces is reported. The density and shapes of the nano grooves are controlled by the number of rubbings with a 0.1 ”m diamond lapping film, achieving mobility values exceeding 3 cm 2 Vs â1 on SiO 2 /Siâthreeâfold higher than that of the conventional spinâcoating method. This process improves the crystalline structure of semiconductor films, facilitating Ï-Ï stacking and largeâsized crystalline structures. Additionally, the solvent treatment on the surface of stretchable Au electrodes effectively reduces the contact resistance with highly oriented polymer semiconductors in intrinsically stretchable transistors, exhibiting 2.66 cm 2 Vs â1 mobility and 0.96 pA offâcurrent at 10 ”m short channel length. The electrical properties of stretchable transistors yield only minor variations under 50% strain conditions and after 1000 cycles at 40% strain.