For thermal stability in perovskite solar cells, we employed a zwitterion-modified electron transport (ETL) layer with a dopant-free hole transport layer (HTL). To modify ETL, a zwitterionic compound, 3-(1-pyridinio)-1-propanesulfonate is dooped in to SnO2 ETL. There are few advantages for a zwitterionic compound since they form interfacial dipoles. First, zwitterion causes work function of SnO2 work function shifts. Second, they pulls electrons from perovskite layers to the border between ETL and pervoskite layer to enhance ETL performance. At last, postively charged atoms in zwitterion passiviate Pb-I defects enhancing device stability. Because of these advantages, we achieved power converstion efficiency of 21.43% with spiro-OMeTAD peroveskite solar cell. Furthermore, we also achieved 20.5% efficiency using dopant-free HTL among the highest effiency using dopant-free polymeric HTLs using green solvents. Therefore, this work suggests promsing strategy to solve thermal stability issue in planar perovskite solar cell.