Theory of Light induced Structural Changes in Optoelectronic Organic Materials
Abstract
Unlike rigidly bonded inorganic semiconductors, organic materials have softer interactions which can be altered by excitation. Light induced structural changes can be important and play a key role in photovoltaic degradation, Stokes shifts, exciton transport, charge separation, internal conversion, and recombination. These processes are very challenging to study with available experimental techniques, but with new first principles methods we can determine the mechanisms on the atomic scale and on ultrafast timescales, using GW-Bethe Salpeter and TDDFT approaches. Two specific materials of focus are PCBM containing bulk heterojunctions and hybrid organometallic perovskites, which are of interest for photovoltaics, light emitting diodes, and other optoelectronic applications. In both cases, significant light induced degradation is observed but the mechanisms remain unclear and debated. For PCBMcontaining organic PV, evidence points to dimerization of the fullerene PCBM molecules as the culprit. The perovskites suffer from rapid degradation, which can be related to moisture and oxygen, but also has a purely light driven component, which is hypothesized to relate to rotations of the organic cations. This work will calculate the ultrafast atomic motions after light absorption in both materials, revealing the detailed pathways to degradation in both materials. The results will point the way to how to tune these processes and closely related processes of exciton transport and recombination.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501910236
Entities
People
- David A Strubbe
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of California