Exfoliated Fluorographene Quantum Dots as Outstanding Passivants for Improved Flexible Perovskite Solar Cells.

Flexible perovskite solar cells (PSCs) are currently one of the most attractive flexible thin-film photovoltaic technologies. Despite achieving remarkable progress in power conversion efficiencies (PCEs), flexible PSCs have not yet kept pace with rigid PSCs. Defect passivation is of crucial importance to further enhance the PCEs of flexible PSCs. Here, highly-dispersed fluorographene quantum dots (FGQDs) are exfoliated from fluorinated graphite with the aid of stirring and sonication and used to passivate the grain boundaries and surface of the perovskite films for high-performance flexible PSCs. Photoluminescence spectroscopy (PL) and time-resolved PL decays indicate that the FGQDs are beneficial for suppressing carrier recombination. Space-charge-limited current measurements prove that the passivated perovskite film exhibits reduced trap densities. As a result, a best PCE of 20.40% is achieved from the flexible PSCs, owing to significantly reduced charge recombination. Moreover, the champion device delivers an outstanding steady-state PCE exceeding 20%. The flexible PSCs with the FGQDs also exhibit enhanced thermal stability and environmental stability. Our work not only highlights the importance of passivating the defects within the perovskite films for high-efficiency flexible PSCs but also offers a promising future for the commercialization of flexible PSCs.