On the efficiency limits of artificial and ultrafast light‐funnels

Abstract

AbstractMany researchers are recently working on artificial light‐harvesters that funnel energy onto high‐performance photovoltaics. However, similar to the theoretical photovoltaic Shockley‐Queisser limit, there are also physical limits in the maximum efficiency of funneling light energy. Unfortunately, they are very complex and depend on many opposing molecular as well as macroscopic structure factors. For example, higher pigment concentrations absorb more sun‐light but lead also to higher, intrinsic reabsorption losses. Molecular orientations increasing incoming light absorption can also increase re‐emission losses back into the same direction. Larger spectral absorption ranges collect more sunlight but simultaneously increase losses due to lower emission photon energies. Larger macroscopic areas of light‐harvesting material decrease the need for expensive photovoltaic materials but also increase molecular re‐absorption losses. Larger pools of energy funneling molecules increase light concentration but also increase energy transfer losses. For finding the optimal overall molecular and macroscopic structure these opposing effects need to be varied within physical feasible boundaries. Here, we present a theoretical assessment that include all necessary molecular and macroscopic parameters and that provided optimized light‐harvesting structures representing a new efficiency bench mark. For highest efficiencies, our results indicate that combined organic molecule/quantum particle systems share many of the optimum spectroscopic characteristics.