High efficiency hysteresis-less inverted planar heterojunction perovskite solar cells with a solution-derived NiO_x hole contact layer

A hysteresis-less inverted planar heterojunction perovskite solar cell with 14.42% power conversion efficiency (PCE) was successfully fabricated by employing a solution-derived NiO_x film as the hole selective contact. Here, the non-stoichiometric transparent NiO_x film is composed of a lot of small NiO_x nanocrystals with a cubic crystal structure. Inverted planar heterojunction perovskite solar cells based on the as-prepared NiO_x hole selective contacts show a much higher PCE and air storage stability than the control device fabricated from the PEDOT:PSS film as the hole selective contact, since NiO_x has a better electron blocking property due to its high conduction band edge position. The thickness of the NiO_x contact strongly influences the performance of the NiO_x-based perovskite solar cells, which include the PCE, hysteresis behaviors and air storage stability due to the thickness-dependent morphology of the NiO_x contact.