Spin-polarized currents induced in antiferromagnetic polymer multilayered field-effect transistors.

A theoretical construction of an antiferromagnetic polymer multilayered field-effect transistor with polymers stretched between the source and drain contacts was undertaken. The model employed a quantum approach to the on-chain spin-charge distribution, which was self-consistently coupled with the charge distribution controlled by the gate voltage. Contrary to standard field-effect transistors, we found that the current firstly increased superlinearly with the drain voltage, then it achieved the maximum for drain voltages notably lower than the gate voltage, and after that, it decreased with the drain voltage with no saturation.

Photophysics of Benzoxazole and Dicyano Functionalised Diketopyrrolopyrrole Derivatives: Insights into Ultrafast Processes and the Triplet State.

Diketopyrrolopyrrole (DPP) functionalised with an electron donating unit acts as a donor-acceptor molecules that have shown potential for application in dyes and photovoltaics. These molecules offer broad absorption/emission properties and structure-dependent dynamics. In this study, we used femtosecond pump-probe spectroscopy to investigate the photo-initiated dynamics of thiophene linked DPP derivatives.

Formation of spin-polarized current in antiferromagnetic polymer spintronic field-effect transistors.

We have theoretically investigated the feasibility of constructing a spintronic field-effect transistor with the active channel made of a polymer chain with the antiferromagnetic coupling oriented in the source-to-drain direction. We found two different device function regimes controlling the on-chain spin-charge carrier density by tuning the gate voltage. At higher charge carrier densities, the source-drain current linearly increases with decreasing charge carrier densities.

Kinetics of the Photoexcited States in Thin Films of Metallo-Supramolecular Polymers With Ditopic Thiophene-Bridged Terpyridine Ligands.

Managing the excited-state decay by a supramolecular structure is a crucial issue for organic photovoltaics. We show that in thin films of metallo-supramolecular polymers made of bis(terpyridine-4'-yl)terthiophenes and coupling ions, the photoexcited states generated by ultrashort laser pulses at the wavelength of 440 nm decay by the bi-molecular annihilation predominantly controlled by the Förster transfer between singlet states. During this bi-molecular annihilation of singlet states, intermediate hot triplet pairs are formed, which subsequently dissociate into long-living diffusing triplet states.

Singlet Fission in Thin Solid Films of Bis(thienyl)diketopyrrolopyrroles.

The singlet fission (SF) process discovered in bis(thienyl)diketopyrrolopyrroles (TDPPs) can boost their potential for photovoltaics (PV). The crystal structures of TDPP analogs carrying n-hexyl, n-butyl, or 2-(adamant-1-yl)ethyl substituents are similar, but contain increasingly slipped stacked neighbor molecules. The observed SF rate constants, k , (7±4), (9±3) and (5.

Impact of Hydrogen Bonds Limited Dipolar Disorder in High-k Polymer Gate Dielectric on Charge Carrier Transport in OFET.

The paper contributes to the characterization and understanding the mutual interactions of the polar polymer gate dielectric and organic semiconductor in organic field effect transistors (OFETs). It has been shown on the example of cyanoethylated polyvinylalcohol (CEPVA), the high-k dielectric containing strong polar side groups, that the conditions during dielectric layer solidification can significantly affect the charge transport in the semiconductor layer. In contrast to the previous literature we attributed the reduced mobility to the broader distribution of the semiconductor density of states (DOS) due to a significant dipolar disorder in the dielectric layer.

Gate voltage impact on charge mobility in end-on stacked conjugated oligomers.

We present a model of the charge transport in thin film organic field-effect transistors with the active channel made of linear conjugated chains stacked on the substrate with end-on-orientation. The transport was simulated in a box consisting of 25 polymer chains, in which the delocalized quantum orbital eigenstates of the on-chain hole distribution were calculated. The inter-chain charge transfer was solved semi-classically.

Plasmonic Screening Effect of Gold Nanoparticles Array on Light Absorption in Poly(3-hexyl)Thiophene Thin Film.

The localized surface plasmon (LSP) photophysical phenomenon occurring in metal nanostructures is often presented as a way to effectively couple light into sub-wavelength-scale photovoltaic devices, which would otherwise suffer from a weak light absorption. The simultaneous complementary effect of localized optical field depletion receives far less attention. We studied a system consisting of a planar gold nanoparticles array (AuNP) deposited at the surface of a semiconducting polymer thin film (P3HT).

On the methodology of the determination of charge concentration dependent mobility from organic field-effect transistor characteristics.

We developed a new methodology for determining charge concentration dependent mobility from organic field-effect transistor (OFET) characteristics, applicable for semiconducting polymers with structural and energy disorder. We show that basic formulae recommended by the "IEEE Standard for Test Methods for the Characterization of Organic Transistors and Materials" for the determination of the field-effect mobility as obtained from the slope Ivs. V (in the saturation regime) or from the transconductance dI/dV (in the linear regime) are not suitable for materials with concentration dependent charge carrier mobility.

Phonons spreading from laser-heated gold nanoparticle array accelerate diffusion of excitons in an underlying polythiophene thin film.

Localized surface plasmon (LSP) photophysical phenomena occurring in metal nanostructures are often presented as a method to effectively couple light into photovoltaic devices of sub-wavelength-scale thickness. However, the excitation of LSP is also associated with rapid energy dissipation leading to local heating, which affects the excitation energy pathway. We studied a system consisting of a planar gold nanoparticle (AuNP) array deposited at the surface of a semiconducting polymer thin film (P3HT).

Modelling of the charge carrier mobility in disordered linear polymer materials.

We introduced a molecular-scale description of disordered on-chain charge carrier states into a theoretical model of the charge carrier transport in polymer semiconductors. The presented model combines the quantum mechanical approach with a semi-classical solution of the inter-chain charge hopping. Our model takes into account the significant local anisotropy of the charge carrier mobility present in linear conjugated polymers.

Time-Resolved Transient Optical Absorption Study of Bis(terpyridyl)oligothiophenes and Their Metallo-Supramolecular Polymers with Zn(II) Ion Couplers.

α,ω-Bis(terpyridyl)oligothiophenes spontaneously assemble with Zn(II) ions giving conjugated constitutional dynamic polymers (dynamers) of the metallo-supramolecular class, which potentially might be utilized in optoelectronics. Their photophysical properties, which are of great importance in this field of application, are strongly influenced by the dynamic morphology. It was assessed in this study by using ultrafast pump-probe optical absorption spectroscopy.

Roles of octabutoxy substitution and J-aggregation in stabilization of the excited state in nickel phthalocyanine.

Nickel phthalocyanine (NiPc) complexes are known to show a rapid nonradiative deactivation of the photoexcited state through the internal conversion. This could be exploited in practical applications, such as photoprotection and photodynamic therapy. The butoxy substitution of NiPc plays an important role for drug delivery but also greatly influences its photophysics.