Preethi Susan Mathew

Chemistry and Biochemistry

Faculty Advisor: Prashant Kamat

Understanding the Effect of Crystallinity on Perovskite Stability

Perovskite solar cells are coming up as the next generation solar cells with predicted cell efficiencies of up to 40 percent. They are much cheaper to produce than Silicon solar cells which are commercially used now. Perovskite materials allow for tuning of their bandgap, making it possible to absorb light of different wavelengths. This is possible by using Mixed Halide Perovskites (MHPs) which typically make use of Bromine and Iodine. However, these MHPs segregate under light irradiation. i.e., under light irradiation, a homogenous MHP separates into Iodide and Bromide rich domains. This significantly reduces the efficiency of a MHP solar cell. 

Increased crystallinity of perovskite films has been proposed as a method to mitigate phase segregation. Phase segregation is promoted at grain boundaries in perovskite films, thus having increased crystallinity, or in other words increased grain size, should reduce phase segregation. This project will explore the effect of crystallinity of perovskite films on phase segregation. Specifically, it will look into how varying the grain size of perovskite thin films changes the extent of phase segregation under irradiation. It will also give a threshold grain size above which films will be stable from phase segregation.