Using impedance spectroscopy and computation, we show that incorporation of multi-walled carbon nanotubes (MWCNTs) in the bulk of the active layer of perovskite-based solar cells reduces charge recombination and increases the open circuit voltage. An similar to 87% reduction in recombination was achieved when MWCNTs were introduced in the planar-heterostructure perovskite solar cell containing mixed counterions. The open circuit voltage (Vac) of perovskite/MWCNTs devices was increased by 70 mV, while the short circuit current density (J(sc)) and fill factor (FF) remained unchanged. (C) 2016 Elsevier B.V. All rights reserved.