The conduction of ions and electrons over multiple length scales is central to the processes that drive the biological world. The multidisciplinary attempts to elucidate the physics and chemistry of ...electron, proton, and ion transfer in biological charge transfer have focused primarily on the nano‐ and microscales. However, recently significant progress has been made on biomolecular materials that can support ion and electron currents over millimeters if not centimeters. Likewise, similar transport phenomena in organic semiconductors and ionics have led to new innovations in a wide variety of applications from energy generation and storage to displays and bioelectronics. Here, the underlying principles of conduction on the macroscale in biomolecular materials are discussed, highlighting recent examples, and particularly the establishment of accurate structure–property relationships to guide rationale material and device design. The technological viability of biomolecular electronics and ionics is also discussed.
Inspired by biological charge transfer, the field of biomolecular electronics has emerged. The ability of biomolecular macroscopic structures to mediate charge transport over millimeter and centimeter length scales, while differentiating between electron or ionic conduction, is explored, along with the different possible mechanisms of conduction. The most plausible applications for biomolecular macroscopic structures are also discussed.
Indigo and its derivatives are dyes and pigments with a long and distinguished history in organic chemistry. Recently, applications of this ‘old’ structure as a functional organic building block for ...organic electronics applications have renewed interest in these molecules and their remarkable chemical and physical properties. Natural‐origin indigos have been processed in fully bio‐compatible field effect transistors, operating with ambipolar mobilities up to 0.5 cm2/Vs and air‐stability. The synthetic derivative isoindigo has emerged as one of the most successful building‐blocks for semiconducting polymers for plastic solar cells with efficiencies > 5%. Another isomer of indigo, epindolidione, has also been shown to be one of the best reported organic transistor materials in terms of mobility (∼2 cm2/Vs) and stability. This progress report aims to review very recent applications of indigoids in organic electronics, but especially to logically bridge together the hereto independent research directions on indigo, isoindigo, and other materials inspired by historical dye chemistry: a field which was the root of the development of modern chemistry in the first place.
Indigo and its derivatives are natural‐origin molecules with a long history, and have been at the center of the development of modern chemistry. Today, these substances are making a come‐back in the field of organic electronics.
Photoactive organic semiconductor substrates are envisioned as a novel class of bioelectronic devices that transduce light into stimulating biological signals with relevance for retinal implants or ...guided cellular differentiation. The direct interface between the semiconductor and the electrolyte gives rise to different competing optoelectronic transduction mechanisms. A detailed understanding of such faradaic or capacitive processes and the underlying material science is necessary to develop and optimize future devices. Here, the problem in organic photoelectrodes is addressed based on a planar p‐n junction containing phthalocyanine (H2Pc) and N,N′‐dimethyl perylenetetracarboxylic diimide (PTCDI). The detailed characterization of photoelectrochemical current transients is combined with spectroscopic measurements, impedance spectroscopy, and local photovoltage measurements to establish a model that predicts quantitatively faradaic or capacitive current transients. The decisive elements of the model are the energy levels present at the interface and the voltage building up in the photoelectrode. The result of the efforts is a comprehensive model of photocapacitive and photofaradaic effects that can be applied to developing wireless bioelectronic photostimulation devices.
Photoelectrochemical current generation is investigated in a planar p‐n junction containing phthalocyanine and N,N′‐dimethyl perylenetetracarboxylic diimide. Transient photocurrent measurements are combined with spectroscopic and microscopic investigations of the heterojunction in contact with an aqueous electrolyte. The result is a comprehensive model of photocapacitive and photofaradaic effects that can be applied to developing wireless bioelectronic photostimulation devices.
Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising ...class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g(-1). To facilitate air-stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition-from solution at low temperature-of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles-from airplanes to quadcopters and weather balloons-for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.
Research on semiconductor photocatalysts for the conversion of solar energy into chemical fuels has been at the forefront of renewable energy technologies. Water splitting to produce H2 and CO2 ...reduction to hydrocarbons are the two prominent approaches. A lesser‐known process, the conversion of solar energy into the versatile high‐energy product H2O2 via reduction of O2 has been proposed as an alternative concept. Semiconductor photoelectrodes for the direct photosynthesis of H2O2 from O2 have not been applied up to now. Photoelectrocatalytic oxygen reduction to peroxides in aqueous electrolytes by hydrogen‐bonded organic semiconductor is observed photoelectrodes. These materials have been found to be remarkably stable operating in a photoelectrochemical cell converting light into H2O2 under constant illumination for at least several days, functioning in a pH range from 1 to 12. This is the first report of a semiconductor photoelectrode for H2O2 production, with catalytic performance exceeding prior reports on photocatalysts by one to two orders of magnitude in terms of peroxide yield/catalyst amount/time. The combination of a strongly reducing conduction band energy level with stability in aqueous electrolytes opens new avenues for this widely available materials class in the field of photo(electro) catalysis.
Semiconductor photoelectrodes for reduction of O2 to H2O2 are reported for the first time, representing an alternative solar‐to‐chemical concept. This reaction is carried out by commercial organic pigments, widely available at low cost. The materials robustly photosynthesize peroxides, operating in a pH range from 1 to 12.
We report ultrathin organic photovoltaic elements optimized to run photofaradaic reactions in biological conditions. We demonstrate concurrent oxygen reduction to hydrogen peroxide and glucose ...oxidation. The devices are powered by deep-red irradiation in the tissue transparency window. We utilize bilayers of phthalocyanine, acting as the light absorber, and perylene diimide, functioning as both electron-acceptor and the hydrogen peroxide evolution electrocatalyst. These heterojunction bilayers are stable when irradiated in simulated physiological conditions, producing photovoltages sufficient to simultaneously drive cathodic oxygen reduction to H2O2 and anodic oxidation of glucose. We find that optimization of the anode metal is critical for sustained photofaradaic reactivity. Our results demonstrate a robust "wet" thin film photovoltaic with potential for physiological applications where localized electrochemical manipulation is desired, in particular the delivery of reactive oxygen species.
The electronics era is flourishing and morphing itself into Internet of Everything, IoE. At the same time, questions arise on the issue of electronic materials employed: especially their natural ...availability and low-cost fabrication, their functional stability in devices, and finally their desired biodegradation at the end of their life cycle. Hydrogen bonded pigments and natural dyes like indigo, anthraquinone and acridone are not only biodegradable and of bio-origin but also have functionality robustness and offer versatility in designing electronics and sensors components. With this Perspective, we intend to coalesce all the scattered reports on the above-mentioned classes of hydrogen bonded semiconductors, spanning across several disciplines and many active research groups. The article will comprise both published and unpublished results, on stability during aging, upon electrical, chemical and thermal stress, and will finish with an outlook section related to biological degradation and biological stability of selected hydrogen bonded molecules employed as semiconductors in organic electronic devices. We demonstrate that when the purity, the long-range order and the strength of chemical bonds, are considered, then the Hydrogen bonded organic semiconductors are the privileged class of materials having the potential to compete with inorganic semiconductors. As an experimental historical study of stability, we fabricated and characterized organic transistors from a material batch synthesized in 1932 and compared the results to a fresh material batch.
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