| 초록 |
The high transparency of graphene, together with its good electrical conductivity and mechanical robustness, enable its use as transparent electrodes in optoelectronic devices such as solar cells. While initial demonstrations of graphene-based organic photovoltaics (OPV) have been promising, realization of scalable technologies remains challenging due to their performance and, critically, poor device reproducibility and yield. In this work, we demonstrate by engineering the interface between graphene and photoactive layers, device performance and yield become close to devices using ITO. Our study confirms that the key issue leading to the poor performance or irreproducibility in graphene-based OPV originates from the graphene interface, and can be addressed by a simple interface modification method introduced in this work. We then show similar approach allows graphene to be used as cathode in inverted OPV geometry, thereby demonstrating the universal application of graphene as transparent conductors for both the anode and cathode. Furthermore, nanostructure-based hybrid photovoltaic structures have gained significant interests because of their potential to achieve directional charge transport pathways and large interfacial areas from well-ordered bulk heterojunction geometry. However, building nanostructures directly on the pristine graphene surface is challenging due to the stable nature of graphene. Via the aforementioned method, we further demonstrate inverted graphene-based hybrid solar cells using two different photoactive materials, conjugated polymers and PbS quantum dots, and ZnO nanowires as the electron transporting layer. The advances demonstrated in this work suggest graphene serves as a viable replacement or alternative for ITO in various photovoltaic device configurations. |
