Solvent Vapor-Assisted Magnetic Manipulation of Molecular Orientation and Carrier Transport of Semiconducting Polymers

Unraveling the Molecular Weight Dependence of High Magnetic Field to Manipulate the Semiconducting Polymer Molecular Orientation

The magnetic alignment of molecules, which exploits the anisotropy of diamagnetic susceptibility, provides a clean and versatile approach to the structural manipulation of semiconducting polymers. Here, the magnetic-alignment dynamics of two molecular-weight (MW) batches of a diketopyrrolopyrrole (DPP)-based copolymer (PDVT-8) were investigated. Microstructural characterizations revealed that the magnetically aligned, high-MW (Mn = 53.7 kDa) PDVT-8 film exhibited a higher degree of backbone chain alignment and film crystallinity compared with the low-MW (Mn = 17.6 kDa) PDVT-8 film grown via the same magnetic alignment method. We found that as the MW increases, the degree of preaggregation of the polymer molecules in solution significantly increases and the aggregation mode changes from H-aggregation to J-aggregation through a cooperative assembly mechanism. These events improved the responsiveness of high-MW polymer molecules to magnetic fields. Field-effect transistors based on the magnetic aligned high-MW PDVT-8 films exhibited a 6.8-fold increase in hole mobility compared to the spin-coated films, along with a mobility anisotropy ratio of 12.6. This work establishes a significant correlation among chain aggregation behavior in solution, polymer film microstructures, magnetic responsiveness, and carrier transport performance in donor-acceptor polymer systems.

Control of Molecular Orientation and Carrier Transport of Thiophene-Based Semiconducting Polymer via Superparamagnetic Nanoparticles Fe3O4@C-Assisted Magnetic Alignment Method

Realizing the high molecular orientation and structurally ordered microstructure of organic semiconductor polymer thin films is beneficial for enhancing the charge transport of conjugated polymers and achieving high-performance organic electronic devices. In this work, we successfully developed large-area highly aligned films of a thiophene-based polymer, namely poly(2,5-bis(3-alkylthiophen-2-yl) thieno [3,2-b] thiophene) (PBTTT), using the magnetic alignment method at a low magnetic field (0.12 T), which was assisted by superparamagnetic nanoparticles Fe3O4@C. The aligned microstructure of the composite films is confirmed by systematic analysis that includes polarized optical microscopy, polarized UV–visible absorption spectroscopy, and an atomic force microscope. Organic field effect transistors based on magnetic aligned composite film exhibit a 2.8-fold improvement in carrier mobility compared with the unaligned films. We hold a formation mechanism that the rapid magnetically induced self-assembly property of Fe3O4@C and its intermolecular interaction with polymer chains are key to the new method of preparing oriented thin films.

Out-of-Plane Alignment of Conjugated Semiconducting Polymers by Horizontal Rotation in a High Magnetic Field

The effective control of film morphology and molecular packing in the out-of-plane direction of semiconductor polymers plays a critical role in governing charge carrier transport in the direction perpendicular to the substrate. In this study, a highly out-of-plane alignment of the n-type polymer P(NDI2OD-T2) film has been successfully achieved by horizontal rotation in a high magnetic field (HR-HMF). The out-of-plane alignment of the P(NDI2OD-T2) film has showed a change from 72% face-on to 98.2% face-on lamellar texture as well as a 1.6-fold increase of the π-π stacking crystalline correlation length compared with that of as-cast polymer films without HR-HMF-induced alignment. Meanwhile, the film with near-perfect face-on molecular packing exhibited more than 18-fold enhancement of electron mobility compared to the unaligned film. The excellent electrical performance achieved with the HR-HMF process indicates its application potential for fabricating high-performance sandwich-type organic electronic devices, such as solar cells and light-emitting diodes.

Recent Developments on Semiconducting Polymer Nanoparticles as Smart Photo-Therapeutic Agents for Cancer Treatments-A Review

Semiconducting polymer nanoparticles (SPN) have been emerging as novel functional nano materials for phototherapy which includes PTT (photo-thermal therapy), PDT (photodynamic therapy), and their combination. Therefore, it is important to look into their recent developments and further explorations specifically in cancer treatment. Therefore, the present review describes novel semiconducting polymers at the nanoscale, along with their applications and limitations with a specific emphasis on future perspectives. Special focus is given on emerging and trending semiconducting polymeric nanoparticles in this review based on the research findings that have been published mostly within the last five years.

Grain Boundary Control of Organic Semiconductors via Solvent Vapor Annealing for High-Sensitivity NO2 Detection

The microstructure of the organic semiconductor (OSC) active layer is one of the crucial topics to improve the sensing performance of gas sensors. Herein, we introduce a simple solvent vapor annealing (SVA) process to control 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) OSC films morphology and thus yields high-sensitivity nitrogen organic thin-film transistor (OTFT)-based nitrogen dioxide (NO₂) sensors. Compared to pristine devices, the toluene SVA-treated devices exhibit an order of magnitude responsivity enhancement to 10 ppm NO₂, further with a limit of detection of 148 ppb. Systematic studies on the microstructure of the TIPS-pentacene films reveal the large density grain boundaries formed by the SVA process, improving the capability for the adsorption of gas molecules, thus causing high-sensitivity to NO₂. This simple SVA processing strategy provides an effective and reliable access for realizing high-sensitivity OTFT NO₂ sensors.