Materials for energy

Perovskite semiconductor is among the most exciting photovoltaic materials, thank for its combine low recombination losses, ease of fabrication, and high spectral tunability, however solar cells made by this material are low stability due to the ionic nature of the perovskite crystal, rendering it highly hygroscopic, and the extensive diffusion of ions especially at increased temperatures. In combination between experiments and first-principle calculations, we show that application of a simple solution-processed perfluorinated self-assembled monolayer (p-SAM) not only enhances the solar cell efficiency, but also improves the stability of the perovskite absorber and, in turn, the solar cell under increased temperature or humid conditions.

The figure shows transition state geometries of the ethylene epoxidation reaction forming of acetaldehyde (top panels) and ethylene oxide (central panels) and top view of the Ag(111), Cu/Ag(111) Cu/Ag(110), and Cu/Ag(100) catalysts.

Chemical reactions, and physical processes at surfaces, interfaces, clusters in gaseous and liquid environments Depending on the operational environment and physical phase, catalysts may act by diverse atomistic mechanisms, which typically include bringing reactants to specific sites, providing them the excitation energy (or transferring the charge) that triggers the formation/breaking of chemical bonds, This project uses the density functional theory (DFT), molecular dynamic, advanced sampling, and kinetic Monte-Carlo methods to investigate the fundamental electronic and structural phenomena, as well as the intermediate stages, of chemical reactions taking place at the heterogenous catalysts. We have applied for two chemical reactions: ethylene epoxidation and carbon monoxide oxidation on different transition metal catalysts and their alloys.

S Piccinin, NL Nguyen, C Stampfl, M Scheffler Journal of Materials Chemistry 20 (46), 10521-10527; NL Nguyen, S de Gironcoli, S Piccinin, The Journal of Chemical Physics 138 (18), 184707