Perovskite solar cells are made of relatively new semiconductors: metal halide perovskites. They have emerged as one of the most promising photovoltaic technologies because of their potentially higher efficiency and lower cost than Si ones. The one remaining challenge is the long-term stability. The state-of-the-art cells are only stable for hundreds of hours. Ion migration as well as chemical reactions are key processes causing degradation. All the above processes are triggered and accelerated by the presence of intrinsic defects in the perovskite and extrinsic device operation stress, such as, thermal stress, light excitation and electrical bias.
In our group, we use computer simulations, combining quantum methods (Density Functional Theory) with classical methods (Molecular Dynamics), to study the complex interplay of the chemistry and physics in this fascinating material. As highlights of our recent progress, we have understood the mechanisms of a major stability issue phase segregation and discovered an effective additive fluoride for effective defect passivation. Both have opened possibilities for designing new perovskite compositions for extended service life of perovskite solar cells. Our future challenges include the development of efficient multiscale methods for understanding the chemical and physical processes in the materials and devices at longer length and larger time scales. With these new tools, we will be able to gain thorough understanding of several instability problems and efficiently design ideal processing parameters for the best compositions for ultimate stable solar cells.