Nav: Home

An ordered route to improved performance

January 10, 2017

Silicon is the dominant material in the production of solar cells. However, perovskites are catching up: they are cheap, flexible and have a promising light-to-electricity conversion efficiency. KAUST researchers are investigating the formation of these perovskites to better understand their properties and gain insight into the design of more efficient devices1.

Metal halide perovskites have three components: a metal (often lead), a halogen (commonly iodine although chlorine or bromine are also candidates) and an organic (usually methylammonium). Thin films of these materials can be created by combining methylammonium iodine (MAI) and a lead salt that provides the additional halogen atoms required, such as PbI2, PbBr2 or PbCl2, in a solvent. A drop on a substrate is quickly rotated to create a film and then heated to form the desired solid polycrystalline perovskite material.

The beauty of this approach is its simplicity; however, what happens during the process is not entirely clear. As a result, reproducibility across laboratories has been unsuccessful, with different groups creating samples with different properties.

Aram Amassian, KAUST Associate Professor of Material Science and Engineering, and fellow researchers from the University's Solar Center used bright X-rays at the Cornell High Energy Synchrotron Source in New York, U.S. to observe this one-step solution-coating process in real time. This technology allowed them to identify that the conversion of the perovskite solution to the perovskite crystalline solid occurs via an intermediate solid state that is highly solvated.

"We show that the nature and the stability of this solvated precursor state is crucial to the reproducibility of the final product," said Amassian.

The team measured the changes in film thickness during spinning with the common solvent N,N-dimethylformamide. Using an optical reflective measurement, the team identified that the thickness of the film evolved over time depending on the ratio of MAI to lead salt and that when the concentration of MAI was increased, the solution thinned much slower, strongly impacting the film's formation behavior. This effect is not evident in other material systems used in other similar technologies, such as organic solar cells, providing the first clue that solvent-solute interactions are very important in halide perovskites.

"We then used synchrotron X-ray scattering during spinning to find out more about this intermediate precursor," explained Amassian. "We identified that the precursor existed in either a crystalline or a disordered state within 15 to 20 s of spinning."

Regardless of time delay, the precursors in the crystalline state were stable in time and converted reliably into perovskite films with consistent microstructure and morphology such that their surface coverage and shape were reproducible. Meanwhile, precursors in the disordered state were sensitive to time, causing large variability in the properties of the resultant material and the performance of the solar cells.

King Abdullah University of Science & Technology (KAUST)

Related Solar Cells Articles:

Solar cells more efficient thanks to new material standing on edge
Researchers from Lund University in Sweden and from Fudan University in China have successfully designed a new structural organization using the promising solar cell material perovskite.
Printable solar cells just got a little closer
A University of Toronto Engineering innovation could make printing solar cells as easy and inexpensive as printing a newspaper.
A big nano boost for solar cells
Solar cells convert light into electricity. While the sun is one source of light, the burning of natural resources like oil and natural gas can also be harnessed.
Game changer for organic solar cells
Researchers develop a simple processing technique that could cut the cost of organic photovoltaics and wearable electronics.
Physics, photosynthesis and solar cells
A University of California, Riverside assistant professor has combined photosynthesis and physics to make a key discovery that could help make solar cells more efficient.
Throwing new light on printed organic solar cells
Researchers at the University of Surrey have achieved record power conversion efficiencies for large area organic solar cells.
A new way to image solar cells in 3-D
Berkeley Lab scientists have developed a way to use optical microscopy to map thin-film solar cells in 3-D as they absorb photons.
Toward 'greener,' inexpensive solar cells
Solar panels are proliferating across the globe to help reduce the world's dependency on fossil fuels.
A new technique opens up advanced solar cells
Using a novel spectroscopic technique, EPFL scientists have made a much-needed breakthrough in cutting-edge photovoltaics.
OU physicists developing new systems for next generation solar cells
University of Oklahoma physicists are developing novel technologies with the potential to impact utility-scale energy generation, increase global energy capacity and reduce dependence on fossil fuels by producing a new generation of high efficiency solar cells.

Related Solar Cells Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".