A simple, fast and general protocol for quantitative analysis of X-ray photoelectron spectroscopy (XPS) data provides accurate estimations of chemical species in graphene and related materials (GRMs). XPS data are commonly used to estimate the quality of and defects in graphene and graphene oxide (GO), by comparing carbon and oxygen 1s XPS peaks, obtaining an O/C ratio. This approach, however, cannot be used in the presence of extraneous oxygen contamination. The protocol, based on quantitative line-shape analysis of C 1s signals, uses asymmetric pseudo-Voigt line-shapes (APV), in contrast to Gaussian-based approaches conventionally used in fitting XPS spectra, thus allowing better accuracy in quantifying C 1s contributions from graphitic carbon (sp 2), defects (sp 3 carbon), carbons bonded to hydroxyl and epoxy groups, and from carbonyl and carboxyl groups. The APV protocol was evaluated on GRMs with O/C ratios ranging from 0.02 to 0.30 with film thicknesses from monolayers to bulk-like (>30nm) layers and also applied to previously published data, showing better results compared to those from conventional XPS fitting protocols. Based uniquely on C 1s data, the APV protocol can quantify O/C ratio and the presence of specific functional groups in GRMs even on SiOx, substrates, or in samples containing water.

Hybrid organic–inorganic halide perovskites have emerged at the forefront of solution‐processable photovoltaic devices. Being the perovskite precursor mixture a complex equilibrium of species, it is very difficult to predict/control their interactions with different substrates, thus the final film properties and device performances. Here the wettability of CH3NH3PbI3 (MAPbI3) onto poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transporting layer is improved by exploiting the cooperative effect of graphene oxide (GO) and glucose inclusion. The glucose, in addition, triggers the reduction of GO, enhancing the conductivity of the PEDOT:PSS+GO+glucose based nanocomposite. The relevance of this approach toward photovoltaic applications is demonstrated by fabricating a hysteresis‐free MAPbI3 solar cells displaying a ≈37% improvement in power conversion efficiency if compared to a device grown onto pristine PEDOT:PSS. Most importantly, VOC reaches values over 1.05 V that are among the highest ever reported for PEDOT:PSS p‐i‐n device architecture, suggesting minimal recombination losses, high hole‐selectivity, and reduced trap density at the PEDOT:PSS along with optimized MAPbI3 coverage.

Large area van der Waals (vdW) thin films are assembled materials consisting of a network of randomly stacked nanosheets. The multiscale structure and the twodimensional (2D) nature of the building block mean that interfaces naturally play a crucial role in the charge transport of such thin films. While single or few stacked nanosheets (i.e., vdW heterostructures) have been the subject of intensive works, little is known about how charges travel through multilayered, more disordered networks. Here, we report a comprehensive study of a prototypical system given by networks of randomly stacked reduced graphene oxide 2D nanosheets, whose chemical and geometrical properties can be controlled independently, permitting to explore percolated networks ranging from a single nanosheet to some billions with roomtemperature resistivity spanning from 10 −5 to 10 −1 Ω•m. We systematically observe a clear transition between two different regimes at a critical temperature T*: Efros−Shklovskii variable-range hopping (ES-VRH) below T* and power law behavior above. First, we demonstrate that the two regimes are strongly correlated with each other, both depending on the charge localization length ξ, calculated by the ES-VRH model, which corresponds to the characteristic size of overlapping sp 2 domains belonging to different nanosheets. Thus, we propose a microscopic model describing the charge transport as a geometrical phase transition, given by the metal−insulator transition associated with the percolation of quasi-one-dimensional nanofillers with length ξ, showing that the charge transport behavior of the networks is valid for all geometries and defects of the nanosheets, ultimately suggesting a generalized description on vdW and disordered thin films.

The chemical modification of electrodes with organic materials is a common approach to tune the electronic and electrostatic landscape between interlayers in optoelectronic devices, thus facilitating charge injection at the electrode/semiconductor interfaces and improving their performance. The use of photochromic molecules for the surface modification allows dynamic control of the electronic and electrostatic properties of the electrode and thereby enables additional functionalities in such devices. Here, we show that the electronic properties of a transparent indium tin oxide (ITO) electrode are reversibly and dynamically modified by depositing organic photochromic switches (diarylethenes) in the form of self-assembled monolayers (SAMs). By combining a range of surface characterization and density functional theory calculations, we present a detailed picture of the SAM binding onto ITO, the packing density of molecules, their orientation, as well as the work function modification of the ITO surface due to the SAM deposition.Upon illumination with ultraviolet and green light, we observe a reversible shift of the frontier occupied levels by 0.7 eV, and concomitantly a reversible work function change of ca. 60 meV. Our results prove the viability of dynamic switching of the electronic properties of the electrode with external light stimuli, which could be used to fabricate ITO-based photo-switchable optoelectronic devices.

During the last decade, electrochemical exfoliation of graphite has aroused great interest from both academia and industry for mass production of graphene sheets. Electrochemically exfoliated graphene oxide (EGO) features a much better tunability than chemically EGO, or even than graphene obtained with ultrasonic exfoliation. Chemical and electrical properties of EGO can be modified extensively, thanks to its step-controllable oxidation process, varying the electrolytes and/or the applied potential. It is thus possible, using tunable electrochemical oxidation, to produce low-defect EGO sheets, featuring both good electric conductivity and good dispersibility in common solvents (e.g., acetonitrile or isopropanol). This greatly facilitates its application in several fields, for example, in flexible electronics. In this work, we correlate the dispersion behavior of EGO with its chemical properties using the relative Hansen solubility parameter, zeta potential values, X-ray photoemission spectroscopy, and Raman analysis. A surface morphology study by atomic force microscopy and transmission electron microscopy analyses also reveals that EGO sheets are multiple structures of (partially oxidized) graphene bilayers. Conductive EGO films could be easily prepared by vacuum filtration on different substrates, obtaining electrical conductivity values of up to ∼10 4 S/m with no need for further reduction procedures.