We have demonstrated a two-step wet-chemical route to prepare dense a SnO2 blocking layer (BL) for boosting efficaciously the optoelectronic performance of mesoporous-TiO2 based perovskite solar cells (PSCs). Through SnCl4 water-bath for moderate time, the surface features of SnO2 BL are availably optimized and recombination loss of the devices is perceptibly suppressed. The influence of bath-time upon the microstructures and photo-electronic properties of SnO2 BL and photovoltaic characteristics of the corresponding PSCs, has been discussed detailedly. Deep-going explorations on charge dynamics confirm that SnCl4 bath would facilitate charge transport, hinder charge accumulation and inhibit nonradiative recombination. Upon the basis of surface decoration of SnO2, we improve the open-circuit photovoltage from 1.02 V of initial cell to 1.06 V, and achieve a maximum photovoltaic efficiency of 17.14% and null hysteresis. Accordingly, the device with large area (1.0 cm(2)) based on modified SnO2 have higher PCE of 14.35% and weaker hysteresis index of 0.019 than its unmodified SnO2 courtpart.