Regensburg 2022 – wissenschaftliches Programm
KFM 4.1: Vortrag
Montag, 5. September 2022, 09:30–09:45, H34
The Electronic Structure of Cs2AgBiBr6 at Room Temperature — •Julian Gebhardt1,2 and Christian Elsässer1,2,3 — 1Fraunhofer Institute for Mechanics of Materials IWM, 79108 Freiburg — 2Cluster of Excellence livMatS at FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, Albert-Ludwigs-University Freiburg, 79104 Freiburg — 3Freiburg Materials Research Center (FMF), Albert-Ludwigs-University Freiburg, 79104 Freiburg
Cs2AgBiBr6 is a stable halide double perovskite with a band gap of about 2.2 eV. Therefore, it is intensively studied as possible lead free alternative to hybrid perovskite solar cell absorber materials such as methylammonium-lead iodide. However, power conversion efficiencies of solar cells with this material have not yet exceeded 3%. A detailed understanding of the electronic structure of this material is difficult, due to the variance of reported data and experimental as well as theoretical difficulties that occur in going beyond a qualitative understanding of such an indirect semi-conductor at device operation temperature. Here we combine self-energy corrected electronic-structure theory including spin-orbit coupling and structural dynamics at room temperature to model and understand this compound in a quantitative manner, and we compare our theoretical findings with experimental ones. Based on an achieved good agreement, we propose that the observed low power conversion efficiencies can be attributed to the density of states in the conduction band region. From the relation between dimensionality and electron conductivity, we suggest a general design principle for absorber material search.