A facile strategy for enhanced performance of inverted organic solar cells based on low-temperature solution-processed SnO2 electron transport layer

High-efficiency organic solar cells (OSCs) based on low-temperature (LT) processed SnO2 electron transport layer (ETL) are promising for their commercial use. However, high density of traps and large contact barrier for carriers at the interface between LT SnO2 and the active layer has been reported. To solve the problem, various interface modifying layer materials, such as PFN, has been introduced. Currently, the fabrication process of such interface modifying layer materials is complex and expensive. Herein, a facile strategy involved a polar solvent ethanolamine (EA) is introduced to modify LT SnO2 surface. By soaking the SnO2 film into EA solution in 2-Methoxyethanol (2-ME), EA can easily anchor into SnO2 film surface and forms a continuous monomolecular layer via dehydration reaction. The whole process is green and highly compatible with a roll-to-roll process. Further study suggests that the deep trap centers on SnO2 surface are substantially reduced and the built-in potential in OSCs is reinforced. Finally, OSCs based on EA-modified SnO2 demonstrated an enhanced power conversion efficiency from 10.71% to 12.45% which was comparable to those based on ZnO (12.26%) under the same experiment parameters. Our work boosts the development of the inverted OSCs with easy fabrication and compatibility with roll-to-roll process.