Quantum Coherence and its Impact on Biomimetic Light-Harvesting

Abstract

The survival of all photosynthetic organisms relies on the initial light harvesting step, and thus, after ~3 billion years of evolution energy capture and transfer has become a highly efficient and effective process. Here we examine the latest developments on understanding light harvesting, particularly in systems that exhibit an ultrafast energy transfer mechanism known as quantum coherence. With increasing knowledge of the structural and function parameters that produce quantum coherence in photosynthetic organisms, we can begin to replicate this process through biomimetic systems providing a faster and more efficient approach to harvesting and storing solar power for the worlds energy needs. Importantly, synthetic systems that display signs of quantum coherence have also been created and the first design principles for synthetic systems utilising quantum coherence are beginning to emerge. Recent claims that quantum coherence also plays a key role in ultrafast charge-separation highlights the importance for chemists, biologists, and material scientists to work more closely together to uncover the role of quantum coherence in photosynthesis and solar energy research.

Geometry, Supertransfer, and Optimality in the Light Harvesting of Purple Bacteria

“…1 Despite the diversity of antenna complexes, the efficiency of excitation energy transfer (EET 2 ) through them is generally high, prompting hopes that understanding EET mechanisms in these complexes will generate new ideas for improving artificial light harvesting. 3,4 In searching for design principles in photosynthetic architectures, it is important to not assume that a particular photosynthetic system is optimized simply because it is a product of billions of years of natural selection. If nothing else, the dramatically different antenna architectures in different plant and bacterial taxa 1 cannot all be optimal.…”

“…Photosynthetic organisms use light-harvesting antenna complexes to absorb light and funnel the resulting excitation energy into a reaction center (RC), where the energy is used to drive charge separation . Despite the diversity of antenna complexes, the efficiency of excitation energy transfer (EET) through them is generally high, prompting hopes that understanding EET mechanisms in these complexes will generate new ideas for improving artificial light harvesting. , …”

Distinguishing the roles of energy funnelling and delocalization in photosynthetic light harvesting

“…The energy collected by the antennas is then transmitted, through excitonic energy transfer (EET) [2], to a reaction center (RC), where it drives the first chemical reactions of photosynthesis. The thorough study of EET in photosynthetic antennas has been motivated, in part, by the prospect of learning how to design more efficient artificial light-harvesting devices [3,4].It has long been recognized that excitons in many photosynthetic complexes are directed toward the RC energetically: if the antennas lie higher in energy than the RC, the excitons can spontaneously funnel to the RC. A more recent discovery is that coherent mechanisms can also enhance light-harvesting efficiency.…”

“…The energy collected by the antennas is then transmitted, through excitonic energy transfer (EET) [2], to a reaction center (RC), where it drives the first chemical reactions of photosynthesis. The thorough study of EET in photosynthetic antennas has been motivated, in part, by the prospect of learning how to design more efficient artificial light-harvesting devices [3,4].…”