Paper is a flexible material, commonly used for information storage, writing, packaging or specialized purposes. It also has strong appeal as a substrate in the field of flexible printed electronics. Many applications, including safety, merchandising, smart labels/packing, chemical/biomedical sensors, require an energy source to power operation. Here we review progress regarding development of photovoltaic and energy storage devices on cellulosic substrates where one or more of the main material layers are deposited via solution processing or printing. Paper can be used simply as the flexible substrate or, exploiting its porous fibrelike nature, as an active film by infiltration or co-preparation with electronic materials. Solar cells with efficiencies of up to  4% on opaque and 9% on transparent substrates have been demonstrated. Recent developments in paper-based supercapacitors and batteries are also reviewed with maximum achieved capacity of 1350 mF cm -2 and 2000 mAh g -1 respectively.Analysing the literature, it becomes apparent that more work needs to be carried out in continuing to improve peak performance, but especially stability and the application of printing techniques, even roll-to-roll, over large areas. Paper is not only environmentally friendly and recyclable, it is thin, flexible, low-weight, biocompatible, and low-cost.

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 The article will comprise both published and unpublished results, on stability during aging, upon electrical, chemical and thermal stress, and will finish with an outlook section related to biological degradation and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.

Self-assembled monolayers (SAMs) derived of 4-methoxy-terphenyl-3'',5''-dimethanethiol (TPDMT) and 4-methoxyterphenyl-4''-methanethiol (TPMT) have been prepared by chemisorption from solution onto gold thin films and nanoparticles. The SAMs have been characterized by spectroscopic ellipsometry, Raman spectroscopy and atomic force microscopy to determine their optical properties, namely the refractive index and extinction coefficient, in an extended spectral range of 0.75-6.5 eV. From the analysis of the optical data, information on SAMs structural organization has been inferred. Comparison of SAMs generated from the above aromatic thiols to well-known SAMs generated from the alkanethiol dodecanethiol revealed that the former aromatic SAMs are densely packed and highly vertically oriented, with a slightly higher packing density and a absence of molecular inclination in TPMT/Au. The thermal behavior of SAMs has also been monitored using ellipsometry in the temperature range 25-500 degrees C. Gold nanoparticles functionalized by the same aromatic thiols have also been discussed for surface enhanced Raman spectroscopy applications. This study represents a step forward tailoring the optical and thermal behavior of surfaces as well as nanoparticles.

Organic field‐effect transistors (OFETs) are key devices in organic electronics, and their performances largely depend on molecular structure and solid‐state organization of the π‐conjugated compounds used as semiconductors. This microreview reports several examples of materials for OFET devices and sensors, which have been selected to highlight the basic criteria of molecular design together with the synthetic logic driving the development of organic semiconductors. Versatile synthetic methodologies enable to optimize properties by tailoring molecular structures and functionalization, thus playing a key role in the progress of OFET technology, and more in general of organic electronics, which is emphasized in the discussion.

We demonstrate the direct bioconjugation of hydrogen-bonded organic semiconductors with two different complex functional proteins in an aqueous environment. The representative semiconductors are epindolidione and quinacridone, materials used in devices in the form of vacuum-evaporated polycrystalline films. First, these molecules in thin films react spontaneously with N-hydroxysuccinimide functionalized linkers: disuccinimidyl suberate and succinimidyl biotinate. The suberate linker is then used to covalently bind the Rhodobacter sphaeroides reaction centre (RC), the key photoenzyme for conversion of light into electrical charges in photosynthetic bacteria. Similarly, the biotin linker is used to bridge streptavidin to the surface of the hydrogen-bonded semiconductor film. Multiple-reflection infrared spectroscopy, water contact angle measurements, and atomic force microscopy are used to verify surface functionalization. The presence and functional integrity of the immobilized proteins are demonstrated by specific experiments: a charge recombination kinetics assay in the case of the RC, and photoluminescence measurements for quantum dot-labelled streptavidin. As key results of our work, we have shown that upon bioconjugation, the semiconductors preserve their favourable electrical properties: as evidenced by photoconductor devices operating under water sensitized by the RC, and thin film transistor measurements before and after bioconjugation. These are enabling steps for using hydrogen-bonded semiconductors as platforms for multifunctional bioelectronics devices

Light machine: The simplest photosynthetic protein able to convert sunlight into other energy forms is covalently functionalized with a tailored organic dye to obtain a fully functional hybrid complex that outperforms the natural system in light harvesting and conversion ability.

Direct arylation of 5-octylthieno[3,4-c]pyrrole-4,6-dione with a series of functionalized aryl iodides via C-H bond activation is demonstrated in a deep eutectic solvent made of choline chloride and urea in non-anhydrous conditions and without exclusion of air. This is the first demonstration of a thiophene-aryl coupling via direct arylation in deep eutectic solvents.

Chemical manipulations of the photosynthetic bacterial reaction center for the implementation of this photoenzyme into bioelectronic devices are overviewed.