[6,6]-Phenyl-C-61-Butyric Acid Methyl Ester/Cerium Oxide Bilayer Structure as Efficient and Stable Electron Transport Layer for Inverted Perovskite Solar Cells

Stability issues and high material cost constitute the biggest obstacles of a perovskite solar cell (PVSC), hampering its sustainable development. Herein, we demonstrate that, after suitable surface modification, the low-cost cerium oxide (CeOx) nanocrystals can be well dispersed in both polar and nonpolar solvents and easily processed into high quality electron transport layers (ETLs). The inverted PVSC with the configuration of NiMgLiO/MAPbI(3)/[6,6]-phenyl-C-61-butyric acid methyl ester (PCBM)/CeOx has achieved a high efficiency up to 18.7%. Especially, the corresponding devices without encapsulation can almost keep their initial PCEs in 30% humidity-controlled air in the dark for 30 days and also show no sign of degradation after continuous light soaking and maximum power point tracking for 200 h in a N-2 atmosphere. These results have been proved to be associated with the dual functions achieved by the PCBM/CeOx bilayer ETLs in both efficient electron extraction and good chemical shielding. Furthermore, an all inorganic interfacial layer based PVSC with the configuration of NiMgLiO/MAPbI(3)/CeOx has also achieved a promising efficiency of 16.7%, reflecting the potential to fabricate efficient PVSCs with extremely low cost.