Molecular ferroelectrics for electrocaloric cooling (MOLECTRA)

• Applicants: Professorin Dr. Anna Grünebohm; Privatdozent Dr. Vladimir V. Shvartsman
• Subject Area: Synthesis and Properties of Functional Materials ; Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 510095586

Molecular ferroelectrics have recently attracted significant research interest due to their photovoltaic properties and also as potential candidates for piezoelectric and energy storage devices. In contrast, their performance in cooling applications via the electrocaloric effect remains mainly unexplored, the fundamental understanding is incomplete and no direct measurements of the electrocaloric effect in these systems have been reported so far. This is surprising considering the fact that they combine low cost, low and tunable transition temperatures, different degrees of freedom and a large latent heat at the phase transition making them very promising in this field. In the project Molectra, we aim to understand the phase transitions and optimize the electrocaloric effect in molecular ferroelectrics. First, we want to fundamentally understand the role of the dipole moment of organic cations and the different contributions of the large latent heat to the electrocaloric effect. Second we want to use this knowledge for the materials optimization. Thereby we will focus on hybrid perovskite single crystals (Me3NCH2XN+)-TM-Y3, (X, Y = Cl, Br, I and TM = Fe, Mn, Zn) that show promising phase diagrams with a morphotropic phase boundary and low Curie temperatures. We will combine theoretical approaches, in particular ab initio (based) atomistic simulations (RUB team) and experimental studies (UDE team) including the first direct electrocaloric measurements of this material class. Both teams have extensive experience in the field of ferroelectric materials, particularly, in the study of the electrocaloric effect.

• DFG Programme: Research Grants
• Major Instrumentation: Infrared camera for ECE measurements
• Instrumentation Group: 5840 Spezielle Infrarot-Detektoren
• Co-Investigator: Professor Dr. Doru Constantin Lupascu