In this work, the efficient and stable planar perovskite solar cells (PSCs) based on CH3NH3PbI3-x(SCN)(x) perovskite layer and low-temperature processed SnO2 electron transport layer (ETL) have been fabricated in ambient air with 70% humility. The maximum processing temperature of the PSCs is only 150 degrees C. The effect of SnO2 solution concentrations on photoelectronic characteristics of the PSCs has been symmetrically investigated. At the optimized SnO2 concentration, the PSCs based on SnO2 ETL (SnO2-PSCs) achieve the champion power conversion efficiency (PCE) of 16.23% and average PCE of 15.82%, being much higher than that of the reference PSCs based on TiO2 ETL. The higher PCE of SnO2-PSCs can be attributed to the improved carrier transfer and collection, and the suppressed charge recombination. Importantly, the SnO2-PSCs without encapsulation demonstrate an excellent long-term stability. After being stored in ambient air with 70% humidity for 30 days, the PCE of the unsealed SnO2-PSCs decay only 15%. This work presents a simple low-temperature solution method to fabricate efficient and stable PSCs in ambient air with high humidity, which is beneficial for future application of PSCs. (c) 2017 Elsevier Ltd. All rights reserved.