Spectroscopic signatures of excited state dynamics in organic materials

In our quest for a green energy supply, the sun is arguably the most promising option. In natural photosynthesis, solar light harvesting has been optimized through a long time of evolution. Understanding the physics of this phenomenon opens avenues to improve man-made solar cells in order to maximize efficiencies. For this reason, research on photosynthesis has blossomed for several decades already.

A potential optimization principles relies on quantum mechanics according to which energy can be transported swiftly as a wave. Recent experiments using ultrashort laser pulses have provided indications that wavelike transport is present in photosynthetic complexes. Nevertheless, the organic molecules constituting such complexes are soft and disordered, as a result of which waves are expected to die out fast. How wavelike behavior can still be retained is therefore an intriguing question.

In this thesis, quantum behavior of energy is considered in a synthetic molecule. By looking at a small molecule, quantum effects can be studied more tractably than in a large photosynthetic complex. Our study shows that wavelike behavior is maintained for longer times due to vibrations of the molecule. Hence, surprisingly, the soft character of organic materials actually have a beneficial impact on wavelike energy transport.

This thesis concludes with a proposal of an ultrafast laser experiment in which quantum effects can be identified with a much higher certainty than the experiments used to date. This helps us to determine the possibility of engineering solar cells with optimized quantum transport.