Jacob Tse-Wei Wang , James M. Ball , Eva M. Barea, Antonio Abate , Jack A Alexander-Webber , Jian Huang , Michael Saliba , Iván Mora-Sero , Juan Bisquert , Henry J. Snaith , and R. J. Nicolas
There has been significant recent interest in solution-processable organic-inorganic perovskite absorbers in solar cells following demonstrations of power conversion efficiencies exceeding the highest reported values for organic and dye-sensitized solar cells. However, to date, the highest efficiencies have been achieved using an electron collection (hole-blocking) layer which still requires sintering at 500 °C for best performance, which is unfavourable for low-cost production, applications on plastic substrates, and fabrication of multi-junction device architectures for even higher efficiencies. Here we report a low-cost, solution-based deposition procedure utilising nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes act as a continuous 2D conductive framework to 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 performances with a power conversion efficiency (PCE) up to 15.6 % under simulated AM 1.5 solar illumination which is comparable to control devices using a standard TiO2 electron collection layer sintered at 500 °C. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly towards the development of low-cost solar cells.