Passivation of SnO2 Layer in Perovskite Solar Cell Applications

• Katelyn Gainer, Material Science, University of Delaware

• William Shafarman, Material Science and Engineering, University of Delaware

Perovskite is a developing material that is used as an alternative to silicon in solar cells as it is a thinner material that is more efficient. The perovskite material acts as the absorbing layer that is sandwiched between the two selective layers: the electron and hole selective layer (ETL and HTL). In this research, the perovskite material is MAPbI3 (Methylammonium Lead Iodide) and the ETL is Tin Oxide (SnO2). In the process of creating a solar cell, MAPbI3 is deposited onto the SnO2 layer in a two step vapor deposition process where PbI2 is deposited first and is then followed by MAI. However, during deposition of MAI, the gas may decompose into HI. HI will react with the SnO2 layer of the sample and etch the material which decreases the stability and efficiency of the cell. Currently, to prevent HI from reacting with SnO2, the MAI is not deposited fully which creates a perovskite film with some residual PbI2 left behind. While the PbI2 can protect the SnO2 layer from HI, it does not have any passivation properties that would enhance the efficiency of the cell nor is residual PbI2 a versatile protection method. Therefore, the goal of this project is to characterize the reactivity of SnO2 and HI and reduce its destructive property on the sample as well as enhance the passivation and efficiency of the cell. This is done through introducing a few protective barriers onto the SnO2 film including ionic salts, SAMs, and fullerenes. Each protective layer is deposited onto the SnO2 layer via spin coating or evaporation before the perovskite film is deposited. The results are determined by characterization testing, including contact angle measurements, optical properties and J-V testing. Implementing protective barriers to perovskite cells will improve the solar cell performance.