A laser‐based patterning technique—compatible with flexible, temperature‐sensitive substrates—for the production of large area reduced graphene oxide micromesh (rGOMM) electrodes is presented. The mesh patterning can be accurately controlled in order to significantly enhance the electrode transparency, with a subsequent slight increase in the sheet resistance, and therefore improve the tradeoff between transparency and conductivity of reduced graphene oxide (rGO) layers. In particular, rGO films with an initial transparency of ≈20% are patterned, resulting in rGOMMs films with a ≈59% transmittance and a sheet resistance of ≈565 Ω sq−1, that is significantly lower than the resistance of ≈780 Ω sq−1, exhibited by the pristine rGO films at the same transparency. As a proof‐of‐concept application, rGOMMs are used as the transparent electrodes in flexible organic photovoltaic (OPV) devices, achieving power conversion efficiency of 3.05%, the highest ever reported for flexible OPV devices incorporating solution‐processed graphene‐based electrodes. The controllable and highly reproducible laser‐induced patterning of rGO hold enormous promise for both rigid and flexible large‐scale organic electronic devices, eliminating the lag between graphene‐based and indium–tin oxide electrodes, while providing conductivity and transparency tunability for next generation flexible electronics.

A facile, fast, non-destructive and roll-to-roll compatible photochemical method for simultaneous partial reduction and doping of graphene oxide (GO) films through ultraviolet laser irradiation in the presence of a Cl2 precursor gas is demonstrated. The photochemical chlorinated GO-Cl films were fully characterized by XPS and Raman measurements, in which grafting of chloride to the edges and the basal plane of GO was confirmed. By tuning the laser exposure time, it is possible to control the doping and reduction levels and therefore to tailor the work function (WF) of the GO-Cl layers from 4.9 eV to a maximum value of 5.23 eV. These WF values match with the HOMO level of most polymer donors employed in OPV devices. Furthermore, high efficiency poly(2,7-carbazole) derivative (PCDTBT):fullerene derivative (PC71BM) based OPVs with GO-Cl as the hole transporting layer (HTL) were demonstrated with a power conversion efficiency (PCE) of 6.56% which is 17.35% and 19.48% higher than that of the pristine GO and PEDOT:PSS based OPV devices, respectively. The performance enhancement was attributed to more efficient hole transportation due to the energy level matching between the GO-Cl and the polymer donor.

We report on post-fabrication, in situ, laser induced reduction of graphene oxide (GO) field effect transistors. Our one-step method is efficient, fast, and elevates the conductivity of GO transistor channels by two orders of magnitude. Compared to other reduction techniques, it is facile and simple since it does not require any stringent experimental conditions. Most importantly, we show here that it can be applied for, in situ, post-fabrication reduction of GO devices without compromising any of its components. The physical properties of the laser-reduced graphene oxide were assessed by micro-Raman and X-ray photoelectron spectroscopy analysis and the electrical properties by electric field effect measurements. The application of this technique in other graphene-based optoelectronic devices, especially those fabricated on inexpensive and temperature sensitive flexible substrates such as plastic, is envisaged. V

Solar-energy harvesting through photovoltaic (PV) conversion is the most promising technology for long-term renewable energy production. At the same time, significant progress has been made in the development of energy-storage (ES) systems, which are essential components within the cycle of energy generation, transmission, and usage. Toward commercial applications, the enhancement of the performance and competitiveness of PV and ES systems requires the adoption of precise, but simple and low-cost manufacturing solutions, compatible with large-scale and high-throughput production lines. Photonic processes enable cost-efficient, noncontact, highly precise, and selective engineering of materials via photothermal, photochemical, or photophysical routes. Laser-based processes, in particular, provide access to a plethora of processing parameters that can be tuned with a remarkably high degree of precision to enable innovative processing routes that cannot be attained by conventional approaches. The focus here is on the application of advanced light-driven approaches for the fabrication, as well as the synthesis, of materials and components relevant to PV and ES systems. Besides presenting recent advances on recent achievements, the existing limitations are outlined and future possibilities and emerging prospects discussed.

Utilization of work-function (WF) tuned graphene oxide derivatives as cathode and anode buffer layers in organic photovoltaics (OPVs) is demonstrated.