Professor Maria Abrahamsson of Chalmers University of Technology

"Charge and energy transfer in solar energy conversion materials – routes to long-lived charge separation and efficient energy conversion using benign materials"

Efficient solar energy conversion, to electricity in a photovoltaic device or to fuels relies on efficient utilization of the absorbed photons, either in energy transfer processes or in charge transfer events. Furthermore, the materials used should meet sustainability requirements which presents new challenges for society.

In a typical solar energy conversion device, many photons are not utilized due to the so-called spectrum losses. One promising approach to higher conversion efficiencies includes using more of the low energy photons through upconversion by triplet-triplet annihilation (TTA-UC) and utilizing the high-energy photons better through singlet fission (SF). Both processes rely on bimolecular interaction and the rates for the different processes need to be controlled and tuned, to avoid destructive pathways and to increase the overall efficiencies of the processes. To some extent rates can be tuned by molecular design, since molecules typically provide tuning opportunities. However, many applications require solid state materials, in which it is often a challenge to maintain efficient energy transfer. Here different approaches to self-organization of SF and TTA-UC chromophores in semi-solid state materials will be discussed. The talk will also cover some recent work on photocatalytic CO2-conversion assemblies based on benign materials.

From Sundin et al, J. Phys. Chem. C 2020, 124, 20794−20805.