In planar perovskite solar cells (PSCs), the carrier recombination at the interface between the TiO 2 and the perovskite is one of the dominant factors that limits the devices performance. To this end, we employ a facile method to introduce an ultrathin SnO 2 at the TiO 2 /perovskite interface, which well-solved this issue and improved the performance of device by significantly enhancing the short circuit current (J sc ) of 3.2 mA cm −2 . The detailed characterizations including photoluminescence, time-resolved photoluminescence decay, electrochemical impedance spectroscopy and space charge limited current indicated that the introduction of SnO 2 layer can reduce the density of trap state at TiO 2 /perovskite interface. As a result, the TiO 2 /SnO 2 based device exhibited facilitated charge extraction and suppressed interfacial carrier recombination. This approach effectively addressed one of the main limitations of PSCs performance and paved an effective passivation method to improve the device performance by interfacial engineering.

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