Highly efficient perovskite solar cells employing SnO2 electron transporting layer derived from a tin oxalate precursor solution

Solution processed SnO2 film has been demonstrated to be an efficient electron transporting layer for perovskite solar cells owning to its outstanding opto-electric properties. At the same time, SnCl2, SnCl4 and their hydrates are the most widely used tin sources for depositing SnO2 films. Herein, we demonstrate that tin oxalate (SnC2O4) can function as an alternative tin source. A fast, clean and energy-saving method is proposed to fabricate SnO2 electron transporting layer at moderate temperature of 180 °C using a precursor solution of SnC2O4 dissolved in hydrogen peroxide. After optimization of the SnC2O4 concentrations, high quality SnO2 films can be obtained, which result in higher power conversion efficiency and better long-term device stability of the corresponding perovskite solar cells compared with the reference solar cells fabricated on commercial SnO2 films. Furthermore, the champion power conversion efficiency has been increased from 20.40% for the reference solar cell to 21.31% for the target solar cell.