Disorder on the nanoscale may be responsible for solar-cell efficiency

April 23, 2014 by Chelsea Whyte   
Disorder on the nanoscale may be responsible for solar-cell efficiency
Methylammonium lead iodide perovskite

(Phys.org) —In the past few years, perovskite solar cells have made large leaps forward in efficiency, recently achieving energy conversion with up to 16 percent efficiency. These simple and promising devices are easy enough to make and are made up of earth abundant materials, but little work has been done to explore their atomic makeup.

Researchers at Brookhaven National Laboratory and Columbia University used high-energy x-rays at the National Synchrotron Light Source (NSLS) to characterize the structure of methylammonium lead iodide (MAPbI3) in titanium oxide – the active material in high-performance . Their results are reported in a paper published online in Nano Letters on November 22, 2013,

Photoluminescent properties of these are thought to depend sensitively on the degree of structural order and defects. To characterize the structure, the researchers used beamline X17A at NSLS to study samples of the MAPbI3. Atomic pair distribution function analysis of x-ray diffraction data revealed that 30 percent of the material forms a tetragonal perovskite phase, while 70 percent exists in a disordered state. The presence of disordered material correlates with strong changes in the photoluminescence and absorbance spectra.

This disordered structure has been undetected by conventional techniques used in previous studies. "This nanostructure is expected to have a significant impact on the optoelectronic properties and device performance of the perovskites," said Simon Billinge, coauthor on the paper and a physicist with a joint appointment at Brookhaven National Laboratory and Columbia University.

For example, the absorption of this composite material, made of both ordered and disordered states, is blue shifted by about 50 meV compared to the bulk perovskite crystalline structure. They also found that disordered MAPbI3 is photoluminescent, while the crystalline material is not.

This new understanding of the structure of these materials will lead to better deposition and processing methods that may increase the performance and efficiency of future .

The high-energy x-ray atomic pair distribution function analysis performed in this paper will be applied to a wide range of even more challenging problems at the higher brightness XPD-2 beamline (PDF) at NSLS-II.

Explore further: Bandgap engineering for high-efficiency solar cell design

More information: "Structure of Methylammonium Lead Iodide Within Mesoporous Titanium Dioxide: Active Material in High-Performance Perovskite Solar Cells." Joshua J. Choi, Xiaohao Yang, Zachariah M. Norman, Simon J. L. Billinge, and Jonathan S. Owen. Nano Letters 2014 14 (1), 127-133. DOI: 10.1021/nl403514x

Related Stories

Bandgap engineering for high-efficiency solar cell design

June 22, 2012

ZnSnP2, an absorber material for solar cells, transitions from an ordered to a disordered structure at high temperatures. Researchers from University College London and the University of Bath have proposed taking advantage ...

Revolutionary solar cells double as lasers

March 28, 2014

Commercial silicon-based solar cells - such as those seen on the roofs of houses across the country - operate at about 20% efficiency for converting the Sun's rays into electrical energy. It's taken over 20 years to achieve ...

Tiny crystals to boost solar

April 2, 2014

A new approach to studying solar panel absorber materials has been developed by researchers in France, Acta Cryst. (2014). B70, 390. The technique could accelerate the development of non-toxic and readily available alternatives ...

Recommended for you

Physicists develop new technique to fathom 'smart' materials

November 26, 2015

Physicists from the FOM Foundation and Leiden University have found a way to better understand the properties of manmade 'smart' materials. Their method reveals how stacked layers in such a material work together to bring ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Apr 23, 2014
But the efficiency is only 16%, wouldn't it be higher if the disordered state was responsible? IT seems to me that the disorder is a hindrance similar to the disorder in the quantum state forbidding fusion.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.