Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Light 'relaxes' crystal to boost solar cell efficiency

06.04.2018

Rice, Los Alamos discovery advances case for perovskite-based solar cells

Some materials are like people. Let them relax in the sun for a little while and they perform a lot better.


Constant illumination was found to relax the lattice of a perovskite-like material, making it more efficient at collecting sunlight and converting it to energy. The stable material was tested for solar cell use by scientists at Rice University and Los Alamos National Laboratory.

Credit: Light to Energy Team/Los Alamos National Laboratory

Usage Restrictions:For news reporting purposes only.

A collaboration led by Rice University and Los Alamos National Laboratory found that to be the case with a perovskite compound touted as an efficient material to collect sunlight and convert it into energy.

The researchers led by Aditya Mohite, a staff scientist at Los Alamos who will soon become a professor at Rice; Wanyi Nie, also a staff scientist at Los Alamos, and lead author and Rice graduate student Hsinhan (Dave) Tsai discovered that constant illumination relaxes strain in perovskite's crystal lattice, allowing it to uniformly expand in all directions.

Expansion aligns the material's crystal planes and cures defects in the bulk. That in turn reduces energetic barriers at the contacts, making it easier for electrons to move through the system and deliver energy to devices.

This not only improves the power conversion efficiency of the solar cell, but also does not compromise its photostability, with negligible degradation over more than 1,500 hours of operation under continuous one-sun illumination of 100 milliwatts per cubic centimeter.

The research, which appears this week in Science, represents a significant step toward stable perovskite-based solar cells for next generation solar-to-electricity and solar-to-fuel technologies, according to the researchers.

"Hybrid perovskite crystal structures have a general formula of AMX3, where A is a cation, M is a divalent metal and X is a halide," Mohite said. "It's a polar semiconductor with a direct band gap similar to that of gallium arsenide.

"This endows perovskites with an absorption coefficient that is nearly an order of magnitude larger than gallium arsenide (a common semiconductor in solar cells) across the entire solar spectrum," he said. "This implies that a 300-nanometer thick film of perovskites is sufficient to absorb all the incident sunlight. By contrast, silicon is an indirect band gap material that requires 1,000 times more material to absorb the same amount of sunlight."

Mohite said researchers have long sought efficient hybrid perovskites that are stable in sunlight and under ambient environmental conditions.

"Through this work, we demonstrated significant progress in achieving both of these objectives," he said. "Our triple-cation-based perovskite in a cubic lattice shows excellent temperature stability at more than 100 degrees Celsius (212 degrees Fahrenheit)."

The researchers modeled and made more than 30 semiconducting, iodide-based thin films with perovskite-like structures: Crystalline cubes with atoms arranged in regular rows and columns. They measured their ability to transmit current and found that when soaked with light, the energetic barrier between the perovskite and the electrodes largely vanished as the bonds between atoms relaxed.

They were surprised to see that the barrier remained quenched for 30 minutes after the light was turned off. Because the films were kept at a constant temperature during the experiments, the researchers were also able to eliminate heat as a possible cause of the lattice expansion.

Measurements showed the "champion" hybrid perovskite device increased its power conversion efficiency from 18.5 percent to 20.5 percent. On average, all the cells had a raised efficiency above 19 percent. Mohite said perovskites used in the study were 7 percent away from the maximum possible efficiency for a single-junction solar cell.

He said the cells' efficiency was nearly double that of all other solution-processed photovoltaic technologies and 5 percent lower than that of commercial silicon-based photovoltaics. They retained 85 percent of their peak efficiency after 800 hours of continuous operation at the maximum power point, and their current density showed no photo-induced degradation over the entire 1,500 hours.

"This work will accelerate the scientific understanding required to achieve perovskite solar cells that are stable," Mohite said. "It also opens new directions for discovering phases and emergent behaviors that arise from the dynamical structural nature, or softness, of the perovskite lattice."

The lead researchers indicated the study goes beyond photovoltaics as it connects, for the first time, light-triggered structural dynamics with fundamental electronic transport processes. They anticipate it will lead to technologies that exploit light, force or other external triggers to tailor the properties of perovskite-based materials.

Co-authors of the paper are research scientist Bo Chen, Rafael Verduzco, an associate professor of chemical and biomolecular engineering and of materials science and nanoengineering, and Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry, all of Rice; graduate student Reza Asadpour and Muhammad Ashraf Alam, the Jai N. Gupta Professor of Electrical and Computer Engineering, of Purdue University; research scientists Jean-Christophe Blancon, Sergei Tretiak and Wanyi Nie of Los Alamos; research assistant professor Constantinos Stoumpos and Mercouri Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern University; Jacky Even and Olivier Durand, professors of physics at the Institute of Electronics and Telecommunications of Rennes, France, and Joseph Strzalka, a physicist at Argonne National Laboratory.

This work was supported by the Department of Energy's Office of Energy Efficiency and Renewable Energy and its Basic Energy Sciences office.

###

Read the abstract at http://science.sciencemag.org/cgi/doi/10.1126/science.aap8671

DOI: 10.1126/science.aap8671

This news release can be found online at http://news.rice.edu/2018/04/05/light-relaxes-crystal-to-boost-solar-cell-efficiency/

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Ajayan Research Group: http://ajayan.rice.edu

Verduzco Lab: http://verduzcolab.blogs.rice.edu

Light to Energy Team (Mohite Lab): http://www.lanl.gov/org/padste/adeps/materials-physics-applications/materials-synthesis-integrated-devices/light-energy/index.php

Rice Department of Materials Science and NanoEngineering: https://msne.rice.edu

George R. Brown School of Engineering: https://engineering.rice.edu

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,970 undergraduates and 2,934 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for quality of life and for lots of race/class interaction and No. 2 for happiest students by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Media Contact

David Ruth
david@rice.edu
713-348-6327

 @RiceUNews

http://news.rice.edu 

David Ruth | EurekAlert!

More articles from Materials Sciences:

nachricht New materials: Growing polymer pelts
19.11.2018 | Karlsruher Institut für Technologie (KIT)

nachricht Why geckos can stick to walls
19.11.2018 | Jacobs University Bremen gGmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

New materials: Growing polymer pelts

19.11.2018 | Materials Sciences

Earthquake researchers finalists for supercomputing prize

19.11.2018 | Information Technology

Controlling organ growth with light

19.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>