SnO2 (Tin oxide) is one of the most successful electron transport layer (ETL) materials in perovskite solar cells (PSCs) because of its low sintering temperature and simple preparation process. Similarly, carbon-based hole transport material-free PSCs (C-PSCs) have been widely studied because of their excellent stability and low price. Therefore, C-PSCs having SnO2 as ETL can be envisaged as a promising PSCs system for commercial flexible equipment. However, studies on this system are still scarce because of its low power conversion efficiency (PCE). In this paper, the electron lifetime and current (J(sc)) of a PSC containing a Li-SnO2/Al2O3 + CH3NH3PbI3/carbon structure are greatly improved by doping lithium into SnO2(Li-SnO2) and sandwiching an Al2O3 interlayer into the Li-SnO2 ETL and CH3NH3PbI3. A PCE of 10.01% is obtained, which is 42.3% higher than a PSC having a SnO2/CH3NH3PbI3/carbon structure. The entire preparation process is very simple and is carried out in an air atmosphere below 200 degrees C (20-40% humidity).