Single nanocrystal spectroscopy identifies the interaction between zero-dimensional CdSe/ZnS nano crystals (quantum dots) and two-dimensional layered tin disulfide as a non-radiative energy transfer, whose strength increases with increasing number of tin disulfide layers. Such hybrid materials could be used in optoelectronic devices such as photovoltaic solar cells, light sensors, and LEDs. Credit: Brookhaven National Laboratory
It paves the way for better optoelectronic apps eg energy-harvesting photovoltaics, light sensors, LEDs. Scientists combined excellent light-harvesting properties of quantum dots with the tunable electrical conductivity of a layered tin disulfide semiconductor. The hybrid material exhibited enhanced light-harvesting properties through the absorption of light by the quantum dots and their energy transfer to tin disulfide, both in laboratory tests and when incorporated into electronic devices.
The work analyzes how light excites the quantum dots (made of a cadmium selenide core surrounded by a zinc sulfide shell), which then transfer the absorbed energy to layers of nearby tin disulfide. “We have come up with an interesting approach to discriminate energy transfer from charge transfer, two common types of interactions promoted by light in such hybrids,” said Prahlad Routh, a graduate student from Stony Brook University. “We do this using single nanocrystal spectroscopy to look at how individual quantum dots blink when interacting with sheet-like tin disulfide. This straightforward method can assess whether components in such semiconducting hybrids interact either by energy or by charge transfer.”
The rate for non-radiative energy transfer from individual quantum dots to tin disulfide increases with an increasing number of tin disulfide layers. But performance in laboratory tests isn’t enough to prove the merits of potential new materials. So the scientists incorporated the hybrid material into an electronic device, a photo-field-effect-transistor, a type of photon detector commonly used for light sensing applications.
The hybrid material dramatically enhanced the performance of the photo-field-effect transistors resulting in a photocurrent response (conversion of light to electric current) that was 500% better than transistors made with tin disulfide material alone.
“This kind of energy transfer is a key process that enables photosynthesis in nature,” said Chang-Yong Nam, a materials scientist at Center for Functional Nanomaterials. “Our device demonstrates the performance benefits realized by using both energy transfer processes and new low-dimensional materials.”
Cotlet concludes, “The idea of ‘doping’ two-dimensional layered materials with quantum dots to enhance their light absorbing properties shows promise for designing better solar cells and photodetectors.” https://www.bnl.gov/newsroom/news.php?a=11829
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