Research On The Design Of Electron Transporting Layer In Perovskite Solar Cells

Electron transporting layer(ETL)plays the role of transporting electrons and blocking holes in perovskite solar cells.We systematically study the effects of SnO2 ETL monolayer,TiO2/SnO2 composite ETL,SnO2/Li-TFSI(Lithium bis(trifluoromethanesulphonyl)imide,C2F6LiNO4S2)composite ETL on the photovoltaic performances of perovskite films and perovskite solar cells.(1)The post-annealing temperatures of SnO2 ETL are adjusted.It is found that the photo-generated electrons in the SnO2/PVK interface can be extracted by Sn02 films most fast when the temperature is set at 150?.Meanwhile,the fabricated perovskite films based on this temperature with best coverage,large crystallinity and high light absorption intensity facilitate the decrease of the concentrations of the trap states in perovskite films,which inhibits the non-radiative recombination.Thus,the short circuit current and fill factor of the devices are improved,leading to increased power conversion efficiency.(2)The constructed TiO2/SnO2 composite ETL through spin-coating a SnO2 layer on the TiO2 ETL can effectively increase the crystallinity,coverage of the perovskite films,decrease the PbI2 defects and the concentrations of trap states in the perovskite films.Meanwhile,the ability of extracting the photo-generated electrons in the SnO2/PVK interface is enhanced.The photovoltaic performances of the fabricated perovskite solar cells are improved.(3)The constructed SnO2/Li-TFSI composite ETL through spin-coating a Li-TFSI modification layer on the SnO2 ETL enhances the ability of transporting and extracting the photo-generated carriers in the Sn02/PVK interface.The short circuit current of the fabricated perovskite solar cells is increased,thus improving the photovoltaic performances of the devices.The result shows that the study on the structural design on ETL can dominantly improve the transporting properties of carriers in the ETL,effectively separate electrons and holes,decrease the recombination in the interface,improve the crystallinity quality of the perovskite films and the photovoltaic conversion efficiency of the devices.This provides important experimental evidence for further performances improvement of perovskite films and perovskite solar cells.