The semiconductor and photovoltaic properties of carbon nitride (CNx) thin films prepared using a reactive magnetron cathodic sputtering technique were investigated both individually and as composites with an organic conjugated polymer, poly(2,2'-bithiophene) (PBT). The CNx films showed an increasing thickness as the deposition power and/or nitrogen content in the gas mixture increase. At low nitrogen content and low deposition power (25-50 W), the film structure was dominated by the abundance of the graphitic sp(2) regions, whereas at higher nitrogen contents and magnetron power CNx films started to demonstrate semiconductor properties, as evidenced by the occurrence of photoconductivity and the development of a space charge region. However, CNx films alone did not show any reproducible photovoltaic properties. The situation changed, however, when CNx was deposited onto conjugated PBT substrates. In this configuration, CNx was found to function as an acceptor material improving the photocurrent generation both in solution and in solid state photovoltaic devices, with the external quantum efficiencies reaching 1% at high nitrogen contents. The occurrence of the donor-acceptor charge transfer was further evidenced by suppression of the n-doping of the PBT polymer by CNx. Nanoscale atomic force microscopy (AFM) and current-sensing AFM data suggested that CNx may form a bulk heterojunction with PBT.

This work presents the first electrochemical quartz crystal microbalance (EQCM) results for vertically-oriented graphene nanosheets (VOGNs) as supercapacitor electrodes. Conventional EQCM technique delivered primary insights on the ionic exchange mechanisms between VOGNs and organic electrolytes, showing a major contribution of anions. A more advanced electrogravimetric methodology, ac-electrogravimetry, was then used to access specific dynamic attributes for each species exchanged at the VOGN electrode surface. Accordingly, under the conditions of this study, anions were confirmed to be the major energy storage vector with high kinetic values and low transfer resistance while cations and free solvent molecules are given nonnegligible supporting roles.