The Application of 2D materials in Photovoltaic Devices

Graphene has shown promising applications in photovoltaic devices for its high carrier mobility and conductivity, high transparency, excellent mechanical flexibility and ultrathin thickness and can be used in solar cells as transparent electrodes or interfacial layers. In this talk, I will introduce our recent work on the applications of graphene and other 2-D material in organic solar cells and perovskite solar cells as follows. (1) Package-free flexible organic solar cells are fabricated with multilayer graphene as top transparent electrodes, which show high power conversion efficiency, excellent flexibility and bending stability. The devices also show good air stability, indicating that multilayer graphene is a promising environmental barrier that can protect the organic solar cells from air contamination. (2) Semitransparent perovskite solar cells are prepared by laminating graphene transparent electrodes on the top for the first time. The device performance is optimized by improving the conductivity of the graphene electrodes and the contact between the graphene and the perovskite active layers during the lamination process. The devices show high power conversion efficiencies when they are illuminated from both sides. (3) Solution exfoliated few layers black phosphorus (BP) can be served as an effective electron transport layer in organic photovoltaics for the first time. The power conversion efficiencies of the BP-incorporated OPVs can be improved to 8.18% in average with the relative enhancement of 11%. The incorporation of BP flakes with the optimum thickness of ~ 10 nm can form cascaded band structure in OPVs, which can facilitate electron transport and enhance the PCEs of the devices.