The Effect Of Electron Transport Layers And Its Interface Optimization On The Photovoltaic Performance Of Perovskite Solar Cells

Attributed to the high optical absorption coefficients and longer carrier lifetime and diffusion length of perovskite film,perovskite solar cells?PSCs?have seen rapid improvements in a few years.The best certified photoelectric conversion efficiency?PCE?has arrived at 23.7%.In perovskite solar cells,charge transfer layers are responsible for the process of carrier injection,transportation and collection,which have great influences on the photovoltaic performance of device.The research contents of this paper include surface modification of electron transport layer?ETL?,application of new hole transport materials and modification of hole transport layer?HTL?.TiO₂ is widely used in PSCs as ETL,however,on the one hand TiO₂ has low electron mobility.On the other hand,there are more defects such as oxygen vacancy on its surface,leading serious carrier recombination.In this paper,a fullerene derivative C60NH₂ was introduced as the modification layer on the surface of TiO₂.The photovoltaic performance of the device was improved with the highest efficiency of18.34%.The results of SEM,XRD indicate that C60NH₂ could promote the crystallization process of perovskite grains,preventing the aggregation of PbI₂ at the grain boundary and thus reducing carrier non-radiative recombination.The results of IV and conductivity test indicate C60NH₂ layer could promote electron transmission at MAPbI₃/TiO₂ interface,improving the efficiency of electron injection.The results of PL indicate that C60NH₂ layer could passivate defects mode on the surface of TiO₂ and inhibit carrier non-radiative recombination.Spiro-OMeTAD,as a widely used HTL,has complex preparation process,high cost and harmful effects on the long-term operation stability of PSC.Zinc porphyrin?ZnPy?,a hole transport material widely used in used in organic photovoltaic devices,was introduced in perovskite solar cells.By choosing suitable preparation technology of ZnPy film,the highest PCE of device with ZnPy was 13.75%,while the highest PCE of device with Spiro-OMeTAD was 16.08%.Although ZnPy devices can not compete with Spiro-OMeTAD devices in photovoltaic performance,the results of hole mobility,conductivity and PL indicate that the gap between the ZnPy and Spiro-OMeTAD is not obvious.In addition,compact ZnPy film can effectively prevent moisture air penetration and enhance the stability of perovskite film.CsPbI₂Br PSCs,which have excellent photovoltaic performance and better operation stability,has developed rapidly in recent years.However,disadvantages like mismatching in energy bands of CsPbI₂Br and HTLs hinder its hole transfer process at CsPbI₂Br/HTL interface.Here,a NiO_X modification layer was introduced into interface of CsPbI₂Br/HTL without PbAC₂.When NiO_X was introduced into the interface between CsPbI₂Br and Spiro-OMeTAD,PCE of the device can reach 9.09%.However,when NiO_X was introduced into the interface between CsPbI₂Br and P3HT,the improvements in photovoltaic performance were not outstanding.The characterizations of hole mobility and conductivity also indicate that in Spiro-OMeTAD devices,the NiO_X modification layer can improve the hole injection efficiency and inhibit the non-radiative recombination of carrier.