The photoconversion efficiency record of silicon-perovskite solar cells exceeds 30% owing to hybrid perovskites ΆPbX3 with organic cations Ά that stabilize the perovskite sublattice not only by ionic bonding but also by non-covalent bonding (that is absent in all-inorganic perovskites). As the lowest-energy electronic transitions mainly involve orbitals of the inorganic skeleton, the optoelectronic properties are determined by the halogen composition X, PbX6 tiltings and rotations, and bulk and surface defects. The main drawbacks of hybrid perovskites are their intrinsic instability towards photoinactive δ-phases and degradation by light, heat, oxygen, and moisture, for example. We address the stability issue from the perspectives of the bulk crystal phases, point defects, and surfaces and interfaces. It is shown that the softness of the lattice allows various organic cations to fit into and bond stronger with the inorganic skeleton than methylammonium and formamidinium, enabling mixed-cation compositions of higher stability.

Dr. Udo Schwingenschlögl is a Professor of Materials Science and Engineering & Applied Physics at King Abdullah University of Science and Technology (KAUST). Prior to joining KAUST in 2009, he worked at the International Center of Condensed Matter Physics in Brasilia, Brazil, and the University of Augsburg, Germany. His research interests in condensed matter physics and first-principles materials modeling focus on 2D materials, interface and defect physics, correlated materials, thermoelectric materials, metal-ion batteries, nanoparticles, and quantum transport.

 All faculty, researchers and students are invited to attend.