Cooling, time in the dark preserve perovskite solar powerMay 17, 2016
LOS ALAMOS, N.M., May 17, 2016 -- A new study has found both the cause and a solution for the pesky tendency of perovskite solar cells to degrade in sunlight, a research breakthrough potentially removing one roadblock to commercialization for this promising technology. In a key finding, researchers at Los Alamos National Laboratory have found those degraded devices exhibit self-healing powers when given a little time in the dark. The team determined that photo-degradation in perovskite cells is a purely electronic process due to charge accumulation without chemical damage to the crystal structure and therefore can be reduced, while the cells' self-healing properties allow them to rebound in the dark.
"We can stabilize the device performance by controlling the environmental temperature," said Wanyi Nie, lead researcher on the paper published today in Nature Communications. "The degradation of the devices can be suppressed by simply lowering the temperature by few degrees, that is, from 25 degrees Celsius to 0 degrees Celsius."
The team, lead by Aditya Mohite from the Los Alamos "Light to Energy" team in the Material Synthesis and Integrated Devices group, is exploring organometallic halide semiconducting perovskite solar cells. They are promising because of their high power conversion efficiency (PCE) exceeding 20 percent and the low fabrication costs -- the perovskite material is synthesized via a low-temperature solution process. While achieving high PCE is important, the successful transition from a proof-of-concept experiment to actual market-viable photovoltaic technology requires the device to operate with stability under continuous sunlight, of course, and in the air and humidity of outdoor conditions.
The problem of stability against ambient air/humidity can be circumvented through encapsulation schemes, but the photo-stability of the perovskite-based devices remained an open question. As noted in the literature, these solar cells will undergo degradation with constant light soaking even when the device is under vacuum. Such degradation over time with solar illumination could undermine the commercialization of perovskite-based solar cells.
The new paper, "Light-activated photocurrent degradation and self-healing in perovskite solar cells" (DOI: 10.1038/ncomms11574), co-authored by Wanyi Nie and Jean-Christophe Blancon, describes the photo-degradation process. "What we found in this study is that under constant 1-sun illumination the large-grain perovskite solar cells degrade majorly in terms of the photocurrent," Nie said. "But what's interesting is that the devices can self-heal when sitting in the dark for a short while."
By performing extensive device and spectroscopy characterization, the team found that sunlight triggers the activation of meta-stable trap states at relatively low energy deep in the perovskite bandgap, which results in the trapping and captures of photo-generated charge carriers. Over time, trapped carriers can further accumulate in the device, reducing the photocurrent. On the other hand, placing the solar cell devices in the dark for several minutes allows for "evacuation" of these trapped charges, thus leading to the recovery of the pristine device performances upon the next operation cycle. The team also found that these processes are strongly temperature dependent, and that temperature control over a range of a few tens of degrees can either circumvent the activation of the photo-degradation mechanisms or speed-up the self-healing process.
After exploring several possible physical mechanisms to explain the microscopic origin of the formation of these trap states, joint experimental and theoretical investigations concluded that the most possible scenario is the creation of small polaronic states involving lattice strain and molecular re-orientations of the organic cation present in the perovskite lattice.
"Although several theoretical works have predicted the important role of the organic cation (CH3NH3) in organometallic halide perovskite, it is one of the first joint experimental-theoretical reports on the observation of its impact on the properties of perovskite materials and devices," Blancon said. "Our understanding of the organic cation is still primitive, but our work demonstrates its utmost importance in the photo-stability of perovskite devices and calls for further investigations in the future."
Most importantly this study will provide researchers across the world a first solution to the photo-stability issue in perovskite devices, and future research is now underway toward improvements and the long term technological viability of perovskite-based photovoltaics.
Hybrid perovskite materials, crystalline semiconductors that can be processed from solution at low temperature, have excellent opto-electronic properties that have enabled a wide variety of device applications. Los Alamos has been one of the leaders in the hybrid perovskite photovoltaic research community. By solving the stability problem, the team is ready to apply the material in other applications related to US energy security.
The work at Los Alamos National Laboratory was supported by DOE Office of Basic Energy Sciences and by the Los Alamos Laboratory Directed Research and Development program. This work was done in part at the Center for Integrated Nanotechnologies, a DOE Office of Science User Facility at Los Alamos. Computational and the DFT calculations performed used resources provided by the Los Alamos Institutional Computing Program, supported by the US Department of Energy National Nuclear Security Administration. The work at Purdue University was supported by a Bay Area Photovoltaic Consortium (BAPVC). The work in France was supported by Cellule Energie du CNRS (SOLHYB- TRANS Project) and the University of Rennes 1 (Action Incitative, Défis Scientifique Emergents 2015). This research used resources of the Center for Functional Nanomaterials, which is a US DOE Office of Science Facility, at Brookhaven National Laboratory.
About Los Alamos National Laboratory
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, BWXT Government Group, and URS, an AECOM company, for the Department of Energy's National Nuclear Security Administration.
Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction and solving problems related to energy, environment, infrastructure, health and global security concerns.
DOE/Los Alamos National Laboratory
Related Solar Cells Articles:
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.
A University of Toronto Engineering innovation could make printing solar cells as easy and inexpensive as printing a newspaper.
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.
Researchers develop a simple processing technique that could cut the cost of organic photovoltaics and wearable electronics.
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.
Researchers at the University of Surrey have achieved record power conversion efficiencies for large area organic solar cells.
Berkeley Lab scientists have developed a way to use optical microscopy to map thin-film solar cells in 3-D as they absorb photons.
Solar panels are proliferating across the globe to help reduce the world's dependency on fossil fuels.
Using a novel spectroscopic technique, EPFL scientists have made a much-needed breakthrough in cutting-edge photovoltaics.
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:
The Complete Guide About Solar Energy: A Practical Beginners Guide To Solar Panels, Cells and Electricity
by Russel Hobbs (Author)
Discover Right Now How To Harness Solar Energy More Efficiently
SPECIAL OFFER: OVER 50% DISCOUNT
BUY TODAY FOR ONLY $6.99!
(regularly priced at $14.99)
This book has been designed to take you through the numerous stages of gathering your solar panels equipment and how to harness solar radiation by checking different topographical areas or checking your home’s landscape to detect where you can get most sunshine for your solar panels. With the book, you may or may not need the help of professional Solar panel installer, because the... View Details
Physics of Solar Cells: From Basic Principles to Advanced Concepts
by Peter WÃ¼rfel (Author)
Based on the highly regarded and extremely successful first edition, this thoroughly revised, updated and expanded edition contains the latest knowledge on the mechanisms of solar energy conversion.
The textbook describes in detail all aspects of solar cell function, the physics behind every single step, as well as all the issues to be considered when improving solar cells and their efficiency.
Requiring no more than standard physics knowledge, the book enables both students and researchers to understand the factors driving conversion efficiency and to apply this knowledge to their... View Details
The Physics of Solar Cells (Properties of Semiconductor Materials)
by Jenny Nelson (Author)
This book provides a comprehensive introduction to the physics of the photovoltaic cell. It is suitable for undergraduates, graduate students, and researchers new to the field. It covers: basic physics of semiconductors in photovoltaic devices; physical models of solar cell operation; characteristics and design of common types of solar cell; and approaches to increasing solar cell efficiency. The text explains the terms and concepts of solar cell device physics and shows the reader how to formulate and solve relevant physical problems. Exercises and worked solutions are included.
... View Details
Solar Cells: Operating Principles, Technology, and System Applications (Prentice-Hall series in solid state physical electronics)
by Martin A. Green (Author)
Prentice hall series View Details
Build A Solar Hydrogen Fuel Cell System
by Phillip Hurley (Author)
Learn how to construct and operate the components of a solar hydrogen fuel cell system: the fuel cell stack, the electrolyzer to generate hydrogen fuel, simple hydrogen storage, and solar panels designed specifically to run electrolyzers for hydrogen production. Complete, clear, illustrated instructions to build all the major components make it easy for the non-engineer to understand and work with this important new technology.
Featured are the author's innovative and practical designs for efficient solar powered hydrogen production including:
ESPMs (Electrolyzer Specific... View Details
Solar Cell Device Physics, Second Edition
by Stephen Fonash (Author)
There has been an enormous infusion of new ideas in the field of solar cells over the last 15 years; discourse on energy transfer has gotten much richer, and nanostructures and nanomaterials have revolutionized the possibilities for new technological developments. However, solar energy cannot become ubiquitous in the world's power markets unless it can become economically competitive with legacy generation methods such as fossil fuels.
The new edition of Dr. Stephen Fonash's definitive text points the way toward greater efficiency and cheaper production by adding coverage of... View Details
The Physics of Solar Cells: Perovskites, Organics, and Photovoltaic Fundamentals
by Juan Bisquert (Author)
The book provides an explanation of the operation of photovoltaic devices from a broad perspective that embraces a variety of materials concepts, from nanostructured and highly disordered organic materials, to highly efficient devices such as the lead halide perovskite solar cells. The book establishes from the beginning a simple but very rich model of a solar cell, in order to develop and understand step by step the photovoltaic operation according to fundamental physical properties and constraints. It emphasizes the aspects pertaining to the functioning of a solar cell and the... View Details
Physics of Solar Cells: From Basic Principles to Advanced Concepts (No Longer Used)
by Peter WÃ¼rfel (Author), Uli WÃ¼rfel (Author)
The new edition of this highly regarded textbook provides a detailed overview of the most important characterization techniques for solar cells and a discussion of their advantages and disadvantages.
It describes in detail all aspects of solar cell function, the physics behind every single step, as well as all the issues to be considered when improving solar cells and their efficiency. The text is now complete with examples of how the appropriate characterization techniques enable the distinction between several potential limitation factors, describing how quantities that have been... View Details
Solar Cells: Materials, Manufacture and Operation
by Tom Markvart (Author), Luis Castaner (Author)
The capture and use of solar energy has been growing for many years, but only in recent times have advances in design and manufacture allowed us to see the incorporation of solar energy as a significant player in the renewable energy arena.
Solar cells are at the heart of any photovoltaic system and in this book the various types are described and their characteristics reviewed.
Going beyond materials, design and function, ‘Solar Cells’ also covers their testing, monitoring and calibration thus providing a comprehensive account of current activity in this important field of... View Details
Printable Solar Cells (Advances in Hydrogen Production and Storage (AHPS))
by Nurdan Demirci Sankir (Editor), Mehmet Sankir (Editor)
This book provides an overall view of the new and highly promising materials and thin film deposition techniques for printable solar cell applications. The book is organized in four parts. Organic and inorganic hybrid materials and solar cell manufacturing techniques are covered in Part I. Part II is devoted to organic materials and processing technologies like spray coating. This part also demonstrates the key features of the interface engineering for the printable organic solar cells. The main focus of the Part III is the perovskite solar cells, which is a new and promising family of the... View Details