DNA interlayers enhance charge injection in organic field-effect transistors

Fluctuation-induced dispersion forces on thin DNA films

In this work, the calculation of Casimir forces across thin DNA films is carried out based on the Lifshitz theory. The variations of Casimir forces due to the DNA thicknesses, volume fractions of containing water, covering media, and substrates are investigated. For a DNA film suspended in air or water, the Casimir force is attractive, and its magnitude increases with decreasing thickness of DNA films and the water volume fraction. For DNA films deposited on a dielectric (silica) substrate, the Casimir force is attractive for the air environment. However, the Casimir force shows unusual features in a water environment. Under specific conditions, switching sign of the Casimir force from attractive to repulsive can be achieved by increasing the DNA-film thickness. Finally, the Casimir force for DNA films deposited on a metallic substrate is investigated. The Casimir force is dominated by the repulsive interactions at a small DNA-film thickness for both the air and water environments. In a water environment, the Casimir force turns out to be attractive for a large DNA-film thickness, and a stable Casimir equilibrium can be found. The influences of electrolyte screening on the Casimir pressure of DNA films are also discussed at the end. In addition to the adhesion stability, our finding could be applicable to the problems of condensation and decondensation of DNA, due to fluctuation-induced dispersion forces.

Chiral Optoelectronic Functionalities via DNA-Organic Semiconductor Complex

We fabricate the bio-organic field-effect transistor (BOFET) with the DNA-perylene diimide (PDI) complex, which shows unusual chiroptical and electrical functionalities. DNA is used as the chirality-inducing scaffold and the charge-injection layer. The shear-oriented film of the DNA-PDI complex shows how the large-area periodic molecular orientation and the charge transport are related, generating drastically different optoelectronic properties at each DNA/PDI concentration. The resultant BOFET reveals chiral structures with a high charge carrier mobility, photoresponsivity, and photosensitivity, reaching 3.97 cm² V^-1 s^-1, 1.18 A W^-1, and 7.76 × 10³, respectively. Interestingly, the BOFET enables the definitive response under the handedness of circularly polarized light with a high dissymmetry factor of approximately +0.14. This work highlights the natural chirality and anisotropy of DNA material and the electron conductivity of organic semiconducting molecules to be mutually used in significant chiro-optoelectronic functions as an added ability to the traditional OFET.

The Time Scale of Electronic Resonance in Oxidized DNA as Modulated by Solvent Response: An MD/QM-MM Study

The time needed to establish electronic resonant conditions for charge transfer in oxidized DNA has been evaluated by molecular dynamics simulations followed by QM/MM computations which include counterions and a realistic solvation shell. The solvent response is predicted to take ca. 800–1000 ps to bring two guanine sites into resonance, a range of values in reasonable agreement with the estimate previously obtained by a kinetic model able to correctly reproduce the observed yield ratios of oxidative damage for several sequences of oxidized DNA.

Coherent Effects in Charge Transport in Molecular Wires: Toward a Unifying Picture of Long-Range Hole Transfer in DNA

In the framework of a multistep mechanism in which environmental motion triggers comparatively faster elementary electron-transfer steps and stabilizes hole-transfer products, microscopic coherence is crucial for rationalizing the observed yield ratios of oxidative damage to DNA. Interference among probability amplitudes of indistinguishable electron-transfer paths is able to drastically change the final outcome of charge transport, even in DNA oligomers constituted by similar building blocks, and allows for reconciling apparently discordant experimental observations. Properly tailored DNA oligomers appear to be a promising workbench for studying tunneling in the presence of dissipation at the macroscopic level.

Interface Engineering in Organic Field-Effect Transistors: Principles, Applications, and Perspectives

Heterogeneous interfaces that are ubiquitous in optoelectronic devices play a key role in the device performance and have led to the prosperity of today's microelectronics. Interface engineering provides an effective and promising approach to enhancing the device performance of organic field-effect transistors (OFETs) and even developing new functions. In fact, researchers from different disciplines have devoted considerable attention to this concept, which has started to evolve from simple improvement of the device performance to sophisticated construction of novel functionalities, indicating great potential for further applications in broad areas ranging from integrated circuits and energy conversion to catalysis and chemical/biological sensors. In this review article, we provide a timely and comprehensive overview of current efficient approaches developed for building various delicate functional interfaces in OFETs, including interfaces within the semiconductor layers, semiconductor/electrode interfaces, semiconductor/dielectric interfaces, and semiconductor/environment interfaces. We also highlight the major contributions and new concepts of integrating molecular functionalities into electrical circuits, which have been neglected in most previous reviews. This review will provide a fundamental understanding of the interplay between the molecular structure, assembly, and emergent functions at the molecular level and consequently offer novel insights into designing a new generation of multifunctional integrated circuits and sensors toward practical applications.

The Dynamics of Hole Transfer in DNA

High-energy radiation and oxidizing agents can ionize DNA. One electron oxidation gives rise to a radical cation whose charge (hole) can migrate through DNA covering several hundreds of Å, eventually leading to irreversible oxidative damage and consequent disease. Understanding the thermodynamic, kinetic and chemical aspects of the hole transport in DNA is important not only for its biological consequences, but also for assessing the properties of DNA in redox sensing or labeling. Furthermore, due to hole migration, DNA could potentially play an important role in nanoelectronics, by acting as both a template and active component. Herein, we review our work on the dynamics of hole transfer in DNA carried out in the last decade. After retrieving the thermodynamic parameters needed to address the dynamics of hole transfer by voltammetric and spectroscopic experiments and quantum chemical computations, we develop a theoretical methodology which allows for a faithful interpretation of the kinetics of the hole transport in DNA and is also capable of taking into account sequence-specific effects.

Transient and Enduring Electronic Resonances Drive Coherent Long Distance Charge Transport in Molecular Wires

It is shown that the yields of oxidative damage observed in double-stranded DNA oligomers consisting of two guanines separated by adenine-thymine (A:T) _n bridges of various lengths are reliably accounted for by a multistep mechanism, in which transient and nontransient electronic resonances induce charge transport and solvent relaxation stabilizes the hole transfer products. The proposed multistep mechanism leads to results in excellent agreement with the observed yield ratios for both the short and the long distance regime; the almost distance independence of yield ratios for longer bridges ( n ≥ 3) is the consequence of the significant energy decrease of the electronic levels of the bridge, which, as the bridge length increases, become quasi-degenerate with those of the acceptor and donor groups (enduring resonance). These results provide significant guidelines for the design of novel DNA sequences to be employed in organic electronics.

A Biopolymer Heparin Sodium Interlayer Anchoring TiO2 and MAPbI3 Enhances Trap Passivation and Device Stability in Perovskite Solar Cells

Traps in the photoactive layer or interface can critically influence photovoltaic device characteristics and stabilities. Here, traps passivation and retardation on device degradation for methylammonium lead trihalide (MAPbI₃ ) perovskite solar cells enabled by a biopolymer heparin sodium (HS) interfacial layer is investigated. The incorporated HS boosts the power conversion efficiency from 17.2 to 20.1% with suppressed hysteresis and Shockley-Read-Hall recombination, which originates primarily from the passivation of traps near the interface between the perovskites and the TiO₂ cathode. The incorporation of an HS interfacial layer also leads to a considerable retardation of device degradation, by which 85% of the initial performance is maintained after 70 d storage in ambient environment. Aided by density functional theory calculations, it is found that the passivation of MAPbI₃ and TiO₂ surfaces by HS occurs through the interactions of the functional groups (COO^- , SO₃^- , or Na⁺ ) in HS with undersaturated Pb and I ions in MAPbI₃ and Ti⁴⁺ in TiO₂ . This work demonstrates a highly viable and facile interface strategy using biomaterials to afford high-performance and stable perovskite solar cells.

Coating ZnO nanoparticle films with DNA nanolayers for enhancing the electron extracting properties and performance of polymer solar cells

Here we present for the first time polymer solar cells that incorporate biological material that show state of the art efficiencies in excess of 8%. The performance of inverted polymer solar cells was improved significantly after deposition of ZnO nanoparticles (ZnO-NPs) together with a thin deoxyribonucleic acid nanolayer and used as an electron extraction layer (EEL). The ZnO-NPs/DNA double layer improved the rectifying ratio, shunt resistance of the cells as well as lowering the work function of the electron-collecting contact. Importantly, the ZnO-NPs/DNA bilayer enhanced the power conversion efficiency of cells considerably compared to cells with EELs made of only DNA (improvement of 56% in relative terms) or only ZnO-NPs (improvement of 19% in relative terms) reaching a best power conversion efficiency of 8.5%. The ZnO-NPs/DNA double layer cells also outperformed ones made with one of the most efficient previous synthetic composite EELs (i.e. ZnO/PEIE(poly(ethyleneimine)-ethoxylated)). Since all fabrication procedures were carried out at low (<150 °C) or room temperature, we have applied the findings to flexible substrates as well as on glass obtaining a high PCE of 7.2%. The solar cells with the biological/metal-oxide composite EELs also delivered an improvement in the stability (∼20% in relative term) compared to that with ZnO-NPs only. All these findings show that natural materials, in this case DNA, the premium biological material, can be incorporated in organic semiconductor devices in tandem with inorganic devices delivering uncompromising levels of performance as well as significant improvements.

New Horizons for Perovskite Solar Cells Employing DNA-CTMA as the Hole-Transporting Material

We investigate solution-processed low-temperature lead-halide perovskite solar cells employing deoxyribose nucleic acid (DNA)-hexadecyl trimethyl ammonium chloride (CTMA) as the hole-transport layer and (6,6)-phenyl C61 -butyric acid methyl ester (PCBM) as electron-acceptor layer in an inverted p-i-n device configuration. The perovskite solar cells utilizing a bio-based charge-transport layer demonstrate power conversion efficiency values of 15.86 %, with short-circuit current density of 20.85 mA cm(-2) , open circuit voltage of 1.04 V, and fill factor of 73.15 %, and improved lifetime. DNA-based devices maintained above 85 % of the initial efficiency after 50 days in air.

Ultra-Lightweight Resistive Switching Memory Devices Based on Silk Fibroin

Ultra-lightweight resistive switching memory based on protein has been demonstrated. The memory foil is 0.4 mg cm(-2) , which is 320-fold lighter than silicon substrate, 20-fold lighter than office paper and can be sustained by a human hair. Additionally, high resistance OFF/ON ratio of 10(5) , retention time of 10(4) s, and excellent flexibility (bending radius of 800 μm) have been achieved.

Physically Transient Resistive Switching Memory Based on Silk Protein

Physically transient resistive switching devices based on silk protein are successfully demonstrated. The devices can be absolutely dissolved in deionized water or in phosphate-buffered saline in 2 h. At the same time, a reasonable resistance OFF/ON ratio of larger than 10(2) and a retention time of more than 10(4) s are achieved for nonvolatile memory applications.

Tailoring Functional Interlayers in Organic Field-Effect Transistor Biosensors

This review aims to provide an update on the development involving dielectric/organic semiconductor (OSC) interfaces for the realization of biofunctional organic field-effect transistors (OFETs). Specific focus is given on biointerfaces and recent technological approaches where biological materials serve as interlayers in back-gated OFETs for biosensing applications. Initially, to better understand the effects produced by the presence of biomolecules deposited at the dielectric/OSC interfacial region, the tuning of the dielectric surface properties by means of self-assembled monolayers is discussed. Afterward, emphasis is given to the modification of solid-state dielectric surfaces, in particular inorganic dielectrics, with biological molecules such as peptides and proteins. Special attention is paid on how the presence of an interlayer of biomolecules and bioreceptors underneath the OSC impacts on the charge transport and sensing performance of the device. Moreover, naturally occurring materials, such as carbohydrates and DNA, used directly as bulk gating materials in OFETs are reviewed. The role of metal contact/OSC interface in the overall performance of OFET-based sensors is also discussed.

Resistive Switching Memory Devices Based on Proteins

Resistive switching memory constitutes a prospective candidate for next-generation data storage devices. Meanwhile, naturally occurring biomaterials are promising building blocks for a new generation of environmentally friendly, biocompatible, and biodegradable electronic devices. Recent progress in using proteins to construct resistive switching memory devices is highlighted. The protein materials selection, device engineering, and mechanism of such protein-based resistive switching memory are discussed in detail. Finally, the critical challenges associated with protein-based resistive switching memory devices are presented, as well as insights into the future development of resistive switching memory based on natural biomaterials.

Exploring the Potential of Nucleic Acid Bases in Organic Light Emitting Diodes

Naturally occurring biomolecules have increasingly found applications in organic electronics as a low cost, performance-enhancing, environmentally safe alternative. Previous devices, which incorporated DNA in organic light emitting diodes (OLEDs), resulted in significant improvements in performance. In this work, nucleobases (NBs), constituents of DNA and RNA polymers, are investigated for integration into OLEDs. NB small molecules form excellent thin films by low-temperature evaporation, enabling seamless integration into vacuum deposited OLED fabrication. Thin film properties of adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) are investigated. Next, their incorporation as electron-blocking (EBL) and hole-blocking layers (HBL) in phosphorescent OLEDs is explored. NBs affect OLED performance through charge transport control, following their electron affinity trend: G < A < C < T < U. G and A have lower electron affinity (1.8-2.2 eV), blocking electrons but allowing hole transport. C, T, and U have higher electron affinities (2.6-3.0 eV), transporting electrons and blocking hole transport. A-EBL-based OLEDs achieve current and external quantum efficiencies of 52 cd A(-1) and 14.3%, a ca. 50% performance increase over the baseline device with conventional EBL. The combination of enhanced performance, wide diversity of material properties, simplicity of use, and reduced cost indicate the promise of nucleobases for future OLED development.

Reversible conversion of dominant polarity in ambipolar polymer/graphene oxide hybrids

The possibility to selectively modulate the charge carrier transport in semiconducting materials is extremely challenging for the development of high performance and low-power consuming logic circuits. Systematical control over the polarity (electrons and holes) in transistor based on solution processed layer by layer polymer/graphene oxide hybrid system has been demonstrated. The conversion degree of the polarity is well controlled and reversible by trapping the opposite carriers. Basically, an electron device is switched to be a hole only device or vice versa. Finally, a hybrid layer ambipolar inverter is demonstrated in which almost no leakage of opposite carrier is found. This hybrid material has wide range of applications in planar p-n junctions and logic circuits for high-throughput manufacturing of printed electronic circuits.

DNA-assisted photoinduced charge transfer between a cationic poly(phenylene vinylene) and a cationic fullerene

DNA promotes the efficient photoinduced charge transfer between a water-soluble, cationic conjugated polymer and cationic fullerene.

DNA bases thymine and adenine in bio-organic light emitting diodes

We report on the use of nucleic acid bases (NBs) in organic light emitting diodes (OLEDs). NBs are small molecules that are the basic building blocks of the larger DNA polymer. NBs readily thermally evaporate and integrate well into the vacuum deposited OLED fabrication. Adenine (A) and thymine (T) were deposited as electron-blocking/hole-transport layers (EBL/HTL) that resulted in increases in performance over the reference OLED containing the standard EBL material NPB. A-based OLEDs reached a peak current efficiency and luminance performance of 48 cd/A and 93,000 cd/m², respectively, while T-based OLEDs had a maximum of 76 cd/A and 132,000 cd/m². By comparison, the reference OLED yielded 37 cd/A and 113,000 cd/m². The enhanced performance of T-based devices is attributed to a combination of energy levels and structured surface morphology that causes more efficient and controlled hole current transport to the emitting layer.

Sericin for resistance switching device with multilevel nonvolatile memory

Resistance switching characteristics of natural sericin protein film is demonstrated for nonvolatile memory application for the first time. Excellent memory characteristics with a resistance OFF/ON ratio larger than 10(6) have been obtained and a multilevel memory based on sericin has been achieved. The environmentally friendly high performance biomaterial based memory devices may hold a place in the future of electronic device development.

High-efficiency polymer solar cells enhanced by solvent treatment

A significant enhancement of efficiency in thieno[3,4-b]-thiophene/benzodithiophene:[6,6]-phenyl C71-butyric acid methyl ester (PTB7:PC70 BM) solar cells can be achieved by methanol treatment. The effects of methanol treatment are shown in an improvement of built-in voltage, a decrease in series resistance, an enhanced charge-transport property, an accelerated and enlarged charge extraction, and a reduced charge recombination, which induce a simultaneous enhancement in open-circuit voltage (Voc), short-circuit current (Jsc), and fill factor (FF) in the devices.