Photocurrent generation in artificial light-harvesting protein matrices

Global interest in solar energy utilization is driving the search for new materials that allow light harvesting and photocurrent generation under a light stimulus. Light harvesting is also one of the most important natural phenomena, of which photosynthesis is an example, and such natural systems have been as well for photocurrent generation. Inspired by natural light-harvesting complexes, we present here a synthetic and artificial solid-state protein-based biopolymer that facilitates the formation of a photocurrent in a wide range of wavelengths upon the molecular doping of the natural light-harvesting chlorophyll molecules. Interfacing of the doped protein matrix with electrodes yielded a photocurrent in the order of a few microamperes when the matrix was exposed to light. We show a switchable (flipping in the) photocurrent behavior when: 1) the magnitude of the applied bias is changed, 2) the location of the irradiated area is changed with respect to the electrodes, and 3) a gradient doping, enabled by the facile molecular doping approach, is formed. Finally, the synthetic artificial nature of the protein matrix allows the exploration of several light-harvesting cofactors not used in natural systems, where we further show photocurrent generation by doped metal-free porphyrins.