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Dyes inserted into the parallel nanochannels of a fully organic crystal show efficient light conversion over a wide visible spectral region, with 100% conversion from UV to blue light. The Figure shows crystals containing either two (bottom) or three (top) dyes under U v illumination, and a top view of the structure of the dyes inserted into nanochannels

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Systematic control of 3D energy transfer (ET) dynamics is achieved in supramolecular nanostructured host-guest systems using spacer-functionalized guest chromophores. Quantum chemistry-based Monte Carlo simulations reveal the strong impact of the spacer length on the ET dynamics, efficiency, and dimensionality. Remarkably high exciton diffusion lengths demonstrate that there is ample scope for optimizing oligomeric or polymeric optoelectronic devices.Resonant energy transfer (ET) is a fundamental process in light harvesting by biological systems that can also be exploited for funneling electronic excitations in optoelectronic devices. The increasing interest in tailor-made organic conjugated materials for these devices requires a thorough understanding of diffusion-enhanced three-dimensional (3D) ET and modeling of intermolecular interactions beyond the classical Fö rster picture due to the close proximity of the molecules in solid-state device architectures. 1 New preparative approaches, such as supramolecular donor-acceptor systems, 2,3 in hand with a realistic theoretical description might tap the full potential of material design for optimized devices.In recent years, increasing attention has been paid to highly ordered supramolecular nanostructured host-guest compounds (HGCs), based either on organic 4-14 or on inorganic optically inert hosts; 15-17 in such systems, the degree of both energetic and positional disorder is small, leading to enhanced properties for optoelectronic applications. [9][10][11][12]15 In a previous study, we have used the organic nanochannel forming host perhydrotriphenylene (PHTP) to investigate 3D ET processes between weakly coupled chromophores by including rod-like donor (D) and acceptor (A) molecules at low A:D ratios. 9 By running Monte Carlo (MC) simulations and treating ET on a quantumchemical level, we were able to describe 3D ET in these systems quantitatively without using adjustable parameters. In the present study, we go a step further by using donor molecules with terminal alkyl spacer groups to systematically vary the distance between the centers of two adjacent donor moieties from 2 to 6 nm, thus gaining full spatial control of 3D ET. By combining experiments and simulations, we are able to understand the details of electronic excitation dynamics, in particular the length and directionality of exciton diffusion, as a function of intermolecular separation. In this respect, our MC approach provides a flexible toolbox for future design of optimized materials for optoelectronic applications.The systems under study are presented in Figure 1. The donor molecules nSDSB are derived from p,p-distyrylbenzene (DSB) by attaching two terminal H(CH 2 ) n O-substituents of variable lengths (with n the number of carbon atoms). The acceptor molecule quinquethiophene (5T) is added at molar doping ratios (x 5T ) ranging from 10 -4 to 10 -1 . The guest molecules are embedded in the channels of the pseudohexagonal PHTP host lattice, adjacent molecules in the same channel being in van der...