Highly Efficient Flexible Perovskite Solar Cells Using Solution-Derived NiO_x Hole Contacts

A solution-derived NiO_x film was employed as the hole contact of a flexible organic-inorganic hybrid perovskite solar cell. The NiO_x film, which was spin coated from presynthesized NiO_x nanoparticles solution, can extract holes and block electrons efficiently, without any other post-treatments. An optimal power conversion efficiency (PCE) of 16.47% was demonstrated in the NiO_x-based perovskite solar cell on an ITO-glass substrate, which is much higher than that of the perovskite solar cells using high temperature-derived NiO_x film contacts. The low-temperature deposition process made the NiO_x films suitable for flexible devices. NiO_x-based flexible perovskite solar cells were fabricated on ITO-PEN substrates, and a preliminary PCE of 13.43% was achieved.