Nav: Home

Hybrid nanostructure steps up light-harvesting efficiency

June 12, 2019

UPTON, NY--To absorb incoming sunlight, plants and certain kinds of bacteria rely on a light-harvesting protein complex containing molecules called chromophores. This complex funnels solar energy to the photosynthetic reaction center, where it is converted into chemical energy for metabolic processes.

Inspired by this found-in-nature architecture, scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Stony Brook University (SBU) have assembled a nanohybrid structure that contains both biologically derived (biotic) and inorganic (abiotic) materials. They combined a light-harvesting protein from a cyanobacteria, semiconducting nanocrystals (quantum dots), and a two-dimensional (2-D) semiconducting transition metal only one atomic layer thick. Described in a paper published on April 29 in ACS Photonics--a journal of the American Chemical Society (ACS)--this nanostructure could be used to improve the efficiency with which solar cells harvest energy from the sun.

"Today's best solar panels can convert nearly 23 percent of the sunlight they absorb into electricity, but on average, their efficiency ranges between 15 and 18 percent," said corresponding author Mircea Cotlet, a materials scientist in the Soft and Bio Nanomaterials Group at Brookhaven Lab's Center for Functional Nanomaterials (CFN)--a DOE Office of Science User Facility. "If this efficiency can be boosted, more electricity 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."

In designing the nanohybrid, the scientists chose atomically thin 2-D molybdenum diselenide (MoSe2) 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 resistance). They combined MoSe2 with two strong light-harvesting nanomaterials: quantum dots (QDs) and the allophycocyanin (APC) protein from cyanobacteria.

The scientists chose the components based on their light-harvesting properties and engineered the components' band gaps (minimum energy required to excite an electron to participate in conduction) such that a concerted stepwise energy transfer can be promoted through the nanohybrid in a directional manner. In the hybrid, energy flows from light-excited QDs to the APC protein and then to MoSe2. This energy transfer mimics natural light-harvesting systems where surface chromophores (in this case, QDs) absorb light and direct the harvested energy to intermediate chromophores (here, APC) and finally to the reaction center (here, MoSe2).

To combine the different components, the scientists applied electrostatic self-assembly, a technique based on the interactions between electrically charged particles (opposite charges attract; like charges repel). They then used a specialized optical microscope to probe the transfer of energy through the nanohybrids. These measurements revealed that the addition of the APC protein layer increases the energy transfer efficiency of the nanohybrid with single-layer MoSe2 by 30 percent. They also measured the photoresponse of the nanohybrid incorporated into a fabricated FET and found that it showed the highest responsivity relative to FETs containing only one of the components, producing more than double the amount of photocurrent in response to incoming light.

"More light is transferred to MoSe2 in the biotic-abiotic hybrid," said first author and research associate Mingxing Li, who is working with Cotlet in the CFN Soft and Bio Nanomaterials Group. "Increased light transfer combined with the high charge carrier mobilities in MoSe2 means more carriers will be collected by the electrodes in a solar cell device. This combination is promising for boosting device efficiency."

The scientists 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.

"We believe this study represents one of the first demonstrations of a cascaded biotic-abiotic nanohybrid involving a 2-D transition-metal semiconductor," said Li. "In a follow-on study, we will work with theoreticians to more deeply understand the mechanism underlying this enhanced energy transfer and identify its applications in energy harvesting and bioelectronics."
-end-
Co-author Jia-Shiang Chen, an SBU graduate student, contributed to the research and acknowledges support from the DOE Office of Science Graduate Student Research program.

Brookhaven National Laboratory is supported by the U.S. Department of Energy's Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.

Follow @BrookhavenLab on Twitter or find us on Facebook.

DOE/Brookhaven National Laboratory

Related Quantum Dots Articles:

Controlling the charge state of organic molecule quantum dots in a 2D nanoarray
Australian researchers have fabricated a self-assembled, carbon-based nanofilm where the charge state (ie, electronically neutral or positive) can be controlled at the level of individual molecules.
Modified quantum dots capture more energy from light and lose less to heat
Los Alamos National Laboratory scientists have synthesized magnetically-doped quantum dots that capture the kinetic energy of electrons created by ultraviolet light before it's wasted as heat.
Using quantum dots and a smartphone to find killer bacteria
A combination of off-the-shelf quantum dot nanotechnology and a smartphone camera soon could allow doctors to identify antibiotic-resistant bacteria in just 40 minutes, potentially saving patient lives.
Synthesizing single-crystalline hexagonal graphene quantum dots
A KAIST team has designed a novel strategy for synthesizing single-crystalline graphene quantum dots, which emit stable blue light.
US Naval Research Laboratory 'connects the dots' for quantum networks
Researchers at the US Naval Research Laboratory developed a novel technique that could enable new technologies that use properties of quantum physics for computing, communication and sensing, which may lead to 'neuromorphic' or brain-inspired computing.
Quantum rebar: Quantum dots enhance stability of solar-harvesting perovskite crystals
Engineering researchers have combined two emerging technologies for next-generation solar power -- and discovered that each one helps stabilize the other.
2D gold quantum dots are atomically tunable with nanotubes
Gold atoms ski along boron nitride nanotubes and stabilize in metallic monolayers.
Graphene quantum dots for single electron transistors
Scientists from the Higher School of Economics, Manchester University, the Ulsan National Institute of Science & Technology and the Korea Institute of Science and Technology have developed a novel technology, which combines the fabrication procedures of planar and vertical heterostructures in order to assemble graphene-based single-electron transistors of excellent quality.
Quantum dots can spit out clone-like photons
MIT and ETH Zurich researchers have produced coherent single photon emitters, a key component for future quantum computers and communications systems.
Tracking pollen with quantum dots
Most plant species on earth are reliant on insects for pollination, including more than 30% of the food crops we eat.
More Quantum Dots News and Quantum Dots Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.