Direct surface functionalization of transparent carbon nanosheet electrodes for organic photovoltaics

Carbon nanosheets (CNSs) were functionalized by a simple dipping approach using phenylhydrazine-based materials to improve their properties as transparent electrodes. X-ray photoelectron spectroscopy was used to investigate the effects of functionalization on the CNS structure and confirm the successful functionalization of phenyl functional groups containing nitrogen and fluorine atoms onto the CNS surface. The functionalized CNSs showed ~32% lower sheet resistance and an up-shifted work function of ~4.8 eV without sacrificing transmittance after being doped with highly electronegative heteroatoms. Accordingly, the functionalized CNS-electrode-based organic photovoltaics exhibited ~13% higher cell efficiency than those based on bare CNSs. These results suggest that direct surface functionalization could improve the performance of CNSs as transparent electrodes.