Low-temperature processed electron collection layers of graphene/TiO2 nanocomposites in thin film perovskite solar cells

The highest efficiencies in solution-processable perovskite-based solar cells have been achieved using an electron collection layer that requires sintering at 500 °C. This is unfavorable for low-cost production, applications on plastic substrates, and multijunction device architectures. Here we report a low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes provide superior charge-collection in the nanocomposites, enabling the entire device to be fabricated at temperatures no higher than 150 °C. These solar cells show remarkable photovoltaic performance with a power conversion efficiency up to 15.6%. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly toward the development of low-cost solar cells. This work was funded by EPSRC, UK. The authors thank Jin Zhang for experimental assistance. J.T.-W.W. would like to acknowledge Swire Educational Trust for supporting his DPhil study at Oxford. J.M.B. and H.J.S. acknowledge the European Union Seventh Framework Programme under the SANS project (grant 246124), and DESTINY project (grant 316494). A.A. thanks the EPSRC APEX project for financial support. E.M.B, I.M.-S., and J.B. acknowledge support by a project from Generalitat Valenciana (PROMETEO/2009/058).