For plants and some bacteria to absorb incoming sunlight, they rely on chromophores, a light-harvesting protein complex containing molecules. This complex funnels solar energy to the photosynthetic reaction center, where it is converted into chemical energy for metabolic processes.

Scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Stony Brook University (SBU) are inspired by this found-in-nature architecture, and as a result, they have assembled a nanohybrid structure that contains both biologically derived (biotic) and inorganic (abiotic) materials. The team combined a light-harvesting protein from cyanobacteria, semiconducting nanocrystals (quantum dots), and a two-dimensional (2-D) semiconducting transition metal only one atomic layer thick. They described the findings of their research in a paper published in ACS Photonics, a journal of the American Chemical Society (ACS), that nanostructure could be used to improve the efficiency with which solar cells harvest energy from the sun.

A material scientists in the Soft and Bio Nanomaterials Group at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility, and also the corresponding author of the study, Mircea Cotlet, said that today's best solar panels can convert almost 23 percent of the sunlight they absorb into electricity, but on average, their efficiency ranges between 15 and 18 percent. If this efficiency can be boosted, more power can be generated. The assembled biotic-abiotic nanohybrid shows enhanced harvesting of light and generation of electrical charge carriers compared to the 2-D semiconductor-only structure. These properties increase the nanohybrid's response to light when the structure is incorporated into a field-effect transistor (FET), a kind of optoelectronic device.

The team chose atomically thin 2-D molybdenum diselenide (MoSe2), in designing the nanohybrid, as the platform for bottom-up assembly. Molybdenum diselenide is a semiconductor or a material whose electrical conductivity is in between that of a regular conductor (little resistance to the flow of electrical current) and insulator (high strength). They combined MoSe2 with two stable light-harvesting nanomaterials: quantum dots (QDs) and the allophycocyanin (APC) protein from cyanobacteria.

The team proposed that adding APC in between QDs and MoSe2 creates a funnel-like energy-transfer effect due to the way that APC preferentially orients itself relative to MoSe2.

The first author of the study and research associate Mingxing Li, who is working with Cotlet in the CFN Soft and Bio Nanomaterials Group, said that they believe this study represents one of the first demonstrations of a cascaded biotic-abiotic nanohybrid involving a 2-D transition-metal semiconductor. In a follow-on study, the researchers will work with theoreticians to more deeply understand the mechanism underlying this enhanced energy transfer and identify its applications in energy harvesting and bioelectronics.