Abstract
The stability of the perovskite/electron transport layer (ETL) interface is critical for perovskite solar cells due to the presence of ultraviolet (UV) light in the solar spectrum. Herein, we have studied the decomposition process and performance evolution of the perovskite layer in contact with different ETLs under strong ultraviolet irradiation. The normally used SnO2 layer has lower photocatalytic activity in comparison with the TiO2 layer, but the perovskite/SnO2 interface is still severely decomposed along with the formation of hole structures. Such UV light-induced decomposition, on the one hand, leads to the decomposition of the perovskite phase into PbI2 and more seriously, the formed hole structure significantly limits the carrier injection at the interface owing to the separation of the perovskite active layer from ETLs. Under the same conditions, the perovskite/PCBM interface is very stable and maintains a highly efficient carrier injection. There is no significant efficiency degradation of the encapsulated PCBM-based devices measured outdoors for about three months.
Highlights
It has been found that when perovskite solar cells (PSCs) are exposed to light and oxygen, O2À is generated by the reaction of photoelectrons and O2 and it can react with CH3NH3+ from the perovskite crystals; nally, the CH3NH3PbI3 layers degrade rapidly to CH3NH2, PbI2, and I2.9,10 In an atmosphere containing light and moisture, water molecules normally interact with IÀ in the perovskite crystals to cause CH3NH3PbI3 to degrade to CH3NH2, PbI2, and HI.[11]
It has been found that the low light stability is because of the fast interface decomposition, which leads to the decomposition of the perovskite phase into PbI2 and the separation of the perovskite active layer from electron transport layer (ETL)
It has been demonstrated that the interface between the perovskite and the ETL is extremely important for PSCs
Summary
We employed high-intensity UV light to study the stability of the perovskite lms in contact with different ETLs in a nitrogen- lled glovebox. It has been found that the low light stability is because of the fast interface decomposition, which leads to the decomposition of the perovskite phase into PbI2 and the separation of the perovskite active layer from ETL. The PCE of the device based on mp-SnO2 shows slower. Paper degradation than that based on mp-TiO2 ETL, while the PCBMbased device shows no signi cant morphology, composition and PCE degradation under the same testing period
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