Predictive modeling of broad wavelength light-harvesting performance in assemblies of multiple chromophores

Abstract

Developing efficient panchromatic light harvesting systems that exploit the energy available from the entire solar spectrum in an economically feasible and scalable fashion is of great importance. Light harvesting by incorporating multiple chromophores into molecular assemblies such as micelles and vesicles is one method for accomplishing this result. In this paper, we describe panchromatic light harvesting in lipid-based vesicle bilayers that contain a random distribution of lipid-bound chromophores. Numerically exact modeling based on Förster theory is developed to establish the criteria for designing a highly efficient panchromatic light-harvesting unit. An approximate modeling method is also developed to greatly reduce the complexity of the modeling problem. Both the exact and approximate models are verified by designing and experimentally testing an efficient three-chromophore light-harvesting system. For the experiments, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (Rhod) as the lowest energy chromophore, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (NBD) as an intermediate acceptor, and Marina Blue® 1,2-Dihexadecanoyl-sn-Glycero-3-Phosphoethanolamine (MB) as the highest energy absorber (donor) are selected. From chromophore concentrations and R0 values, modeling predicts an overall efficiency of energy transfer to the terminal acceptor greater than ≈0.6 across a broad excitation wavelength range of ≈250 nm. The predicted transfer efficiency is verified by the experimental results. In addition, comparison of the approximate modeling method with both the numerically exact method and experimental results confirms that the computationally efficient approximate method is sufficiently accurate to guide choices of experimental parameters such as chromophore concentration. Overall, these results show predictive design of panchromatic light-harvesting performance can be performed rapidly and efficiently using an approximate kinetic model for randomly distributed assemblies of multiple chromophores.