Date: Tuesday, January 31, 2017
Time: 11:00 am
Speaker: Yang Yang, UCLA
Title: Molecular Foundry/ALS Joint Seminar: Interface and Intermediate Phases Engineering for Achieving Efficient Perovskite Solar Cells
Location: Building 66 Auditorium
The interfacial properties and morphology are two essential factors governing the device performance of perovskite solar cells. The ionic nature enabled the perovskite films with exceptional optoelectronic properties, and make specific optimization strategies different from other PV techniques, e.g. the organic solar cells, and more. In this work, we investigate the role of interfacial chemical interactions for perovskite solar cells, and conclude that the chemical interactions at the interface between the perovskite and electrode dominates the interfacial properties instead of the energy level alignment. Perovskite solar cell with champion efficiency of 18.8% is obtained by modifying the interfacial chemical interactions, which constitute 10% improvement compared to that without modification.
On the other hand, we developed a novel method of vapor-induced-intermediate-phases (VIP) to control the perovskite morphology for extremely high solar energy conversion efficiency. In transition from the precursor to perovskite structure, intermediate phases have demonstrated to be highly important in morphological evolution, but have been limited in the past by both processing methods (one step solution process with DMSO additives) and intermediate phase species (PbI2-MAI-DMSO). Our work reports, for the first time, the generation of various intermediate phases by exposing the precursor films to different saturated solvent vapor atmospheres. With this method, we constructed different intermediate phases to facilitate perovskite film formation. Thereafter, high quality perovskite films were obtained, and a champion power conversion efficiency of 19.2% was achieved as one of the highest planar junction perovskite solar cells reported in literature.
Finally, I will also talk about the recent progress in perovskite LEDs, and OPVs at UCLA.