Constructing amorphous titanium nitride/titanium oxides hybrid electron transporting layer for achieving efficient and stable perovskite solar cells

The electron transport layers (ETLs) play a pivotal role in perovskite solar cells (PSCs), which affect the extraction and transfer of the photo-generated-electrons. To explore a superior ETL material, which can not only improve electron transporting but also reduce interface defects, is extremely important for the development of the PSCs. Herein, a hybrid ETL with amorphous titanium nitride and titanium oxides (a-TiNx/TiO2, abbreviated as TiON) is developed to polish the microstructure of the ETL/perovskite interface. The TiON layer can adjust the bandgap alignment to produce favorable cascade energy levels with perovskite layer and facilitate the carrier transfer at ETL/perovskite interface. Meanwhile, the N atoms in TiON ETL surface can bifacially passivate the buried interface of the perovskite layer and the surface of the TiO2, decreasing uncoordinated Pb2+ and Ti4+ defects and reducing non-radiative recombination. Consequently, the TiON-based MAPbI3 solar cells attain the PCE as high as 21.06 % with an open-circuit voltage of 1.18 V. This research demonstrates that TiON and relative metal nitrides can be promising electron transport materials, which provide a reference to develop more high quality ETLs for photovoltaic application.