Enhanced energy transport in genetically engineered excitonic networks

Abstract

One of the challenges for achieving efficient exciton transport in solar energy conversion systems is precise structural control of the light-harvesting building blocks. Here, we create a tunable material consisting of a connected chromophore network on an ordered biological virus template. Using genetic engineering, we establish a link between the inter-chromophoric distances and emerging transport properties. The combination of spectroscopy measurements and dynamic modelling enables us to elucidate quantum coherent and classical incoherent energy transport at room temperature. Through genetic modifications, we obtain a significant enhancement of exciton diffusion length of about 68% in an intermediate quantum-classical regime.

Exciton Dynamics in Phthalocyanine Molecular Crystals

“…4 Recent studies, however, have shown that an efficient singlet exciton migration can occur in highly ordered supramolecular materials. [6][7][8] In particular, Sung et al. have shown by ultrafast transient fluorescence spectroscopy that in helical π-stacks of perylene bisimides delocalized excitons are initially formed and move coherently along the chain in tens of femtoseconds prior to the excimer formation.…”

“…7 Heechul et al have obtained a tunable light-harvesting material, based on a selfassembled chromophore network controlled by a genetically-engineered virus template, which has exhibited enhanced exciton transport via a partially coherent regime. 8 These recent examples clearly highlight the growing interest for obtaining controllable molecular materials for potential nanophotonic and quantum information applications where excitons move beyond the incoherent transport regime. In this sense, it would be 3 useful to consider model systems for studying partially coherent exciton propagation with a good level of detail.…”

“…16,18 A few examples in related self-assembled systems (porphyrins) have shown that exciton diffusion can efficiently occur by means of a coherent mechanism. 19 Recently, an octa(butyl)-substituted metal-free phthalocyanine, H2-OBPc (1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine, see Figure 1a) has been synthesized and exhibited good crystallinity properties (1D π-stacked arrangements, see Figure 1b) in thin films. 20,21 The high degree of crystallinity of the solution-processed thin films allowed Rawat et al to investigate the correlation between long-range order and the nature of the lowest exciton states of the aggregate.…”

Global coherence of quantum evolutions based on decoherent histories: Theory and application to photosynthetic quantum energy transport

“…After a time τ decoh = γ −1 the histories are fully decohered. Indeed, due to the specific model of decoherence (11), which amounts to projective measurements on |i i| at each site with a rate γ , the system kills the coherence in the site basis, which in turn corresponds to the stable pointer basis for this model [7], i.e., the basis in which the density matrix is forced to be diagonal by the specific decoherence model. On the other hand, and for the same reason, the dynamics starts to build up coherence in the exciton basis |E i E i | [see Fig.…”

“…There is now an emerging consensus that efficient transport in natural and biologically inspired artificial light-harvesting systems builds on a finely tuned balance of quantum coherence and decoherence caused by environmental noise [9][10][11][12][13], a phenomenon known as environment-assisted quantum transport (ENAQT). This paradigm has emerged with clarity in recent years, as modern spectroscopic techniques first suggested that exciton transport within photosynthetic complexes might be coherent over appreciable time scales [14].…”