Scientists hone in on size and environmental influence of the quantum dots used in hybrid solar cells

May 31, 2012

(Phys.org) -- Sometimes to answer big questions, you need to start small-very small. Scientists from Pacific Northwest National Laboratory's Chemical Imaging Initiative did just that when they analyzed cadmium selenide, or CdSe, quantum dots. Quantum dots are nanometer-sized particles that have different optical and electronic properties than their bulk materials. The team showed how size and environment unexpectedly alter the dots' structure. Understanding the chemistry involved in these tiny transformations has applications in hybrid solar cells, where improving the electron mobility can ultimately enhance their overall efficiency and ability to contribute to the nation's energy needs.

The majority of quantum dot studies focus on improving the and collection and the efficiency of the solar cells, but few focus on the underlying chemical mechanics. This study was the first to examine how the surrounding environment and size chemically induce changes in the structure of . Ultimately, elucidating the chemical and the electronic structure interactions of CdSe quantum dots will illustrate mechanisms that will advance the hybrid solar cell technologies.

"Because hybrid have great potential in commercial applications, most folks start by looking at the overall cell efficiency, and the fundamental understanding of the chemical and electronic structure interactions is being overlooked," said Dr. Ajay Karakoti, a PNNL scientist and the study's lead author. "We are trying to understand the fundamental interactions. We want to make sure the chemical and structural integrity do not change. In this case, it did. That was unexpected."

A starting point
Understanding the chemistry involved in these tiny transformations has applications in hybrid solar cells, where improving the electron mobility can ultimately enhance their overall efficiency and ability to contribute to the nation's energy needs.

Various imaging, spectroscopy, and diffraction instruments at EMSL were used to carry out this work. The instruments included micro X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible absorption and emission spectroscopy. Karakoti and co-author Dr. Ponnusamy Nachimuthu were quick to explain that the EMSL user facility simplified access to the diverse instrumentation and personnel skill sets necessary for their research. Combining the spectroscopy with imaging provided the chemical signature along with the spatial distribution of the elements.

While they initially conducted their study using CdSe quantum dots in their native environment and drop-cast on a silicon wafer, this was a small step toward more detailed examinations of quantum dots incorporated in a polymer matrix. Building on this research, the team has expanded its focus in determining the source of defect states in CdSe quantum dots with decreasing size and its role in phase transformation, the electronic structures, and the band alignments.

Explore further: Physicists create new nanoparticle for cancer therapy

More information: Karakoti AS, et al. 2011. "Probing the Size- and Environment-Induced Phase Transformation in CdSe Quantum Dots." The Journal of Physical Chemistry Letters 2(22):2925-2929. DOI: 10.1021/jz201243t

Related Stories

Coated Ultrasmall Quantum Dots Suitable for In Vivo Imaging

Dec 03, 2007

Quantum dots have shown promise in a variety of imaging and therapeutic applications, particularly when they are coated to render them biocompatible. However, such coating can increase the size of quantum dots signficantly, ...

Researchers Develop New Procedure to Synthesize Quantum Dots

Apr 04, 2006

Indiana University-Purdue University Indianapolis (IUPUI) researchers in the Department of Chemistry & Chemical Biology have developed a new procedure for the synthesis of “quantum dots,” as published March 31, 2006 on ...

Recommended for you

Innovative strategy to facilitate organ repair

3 hours ago

A significant breakthrough could revolutionize surgical practice and regenerative medicine. A team led by Ludwik Leibler from the Laboratoire Matière Molle et Chimie (CNRS/ESPCI Paris Tech) and Didier Letourneur ...

Physicists create new nanoparticle for cancer therapy

Apr 16, 2014

A University of Texas at Arlington physicist working to create a luminescent nanoparticle to use in security-related radiation detection may have instead happened upon an advance in photodynamic cancer therapy.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

chthonic
not rated yet May 31, 2012
I'm so tired of people's misuse of a certain verb that I'm going to go hone and spend some time with my honing pigeons.

More news stories

'Exotic' material is like a switch when super thin

(Phys.org) —Ever-shrinking electronic devices could get down to atomic dimensions with the help of transition metal oxides, a class of materials that seems to have it all: superconductivity, magnetoresistance ...

Innovative strategy to facilitate organ repair

A significant breakthrough could revolutionize surgical practice and regenerative medicine. A team led by Ludwik Leibler from the Laboratoire Matière Molle et Chimie (CNRS/ESPCI Paris Tech) and Didier Letourneur ...

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Continents may be a key feature of Super-Earths

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...