New Materials, Devices, and Processes for Advanced Concepts
Computational Science and Theory
We can use high-performance computing tools in modeling and simulation studies of semiconductor and other solar materials. We also determine the performance of solar devices. Theoretical studies can help us understand underlying physical principles or predict useful chemical compositions and crystalline structures.
NREL has strong complementary research capabilities in organic photovoltaic (OPV) cells, transparent conducting oxides (TCOs), combinatorial (combi) methods, and atmospheric processing. From fundamental physical studies to applied research relating to solar industry needs, we are developing the new materials, device structures, and tools needed to create polymer-based solar cells that are flexible, lightweight, and inexpensive.
Our primary work focuses on photovoltaic (PV) cell research. But our advances in understanding and creating new materials and processes are also being applied in such areas as organic light-emitting diodes (OLEDs) and thin-film-transistor displays.
OPV is a rapidly emerging PV technology with improving cell efficiency (currently > 8%), encouraging initial lifetime (>5,000 hours unencapsulated), and potential for roll-to-roll manufacturing processes. The building-integrated PV market may find OPV especially attractive because of the availability of absorbers in several different colors and the ability to make efficient transparent devices.
OPV's great strength lies in the diversity of organic materials that can be designed and synthesized for the absorber, acceptor, and interfaces. Considering the Department of Energy's SunShot Initiative goals, we need to further improve efficiency and lifetime. We must understand the fundamentals of device operation, including charge-separation processes, device physics, and interfacial effects. This will allow us to design more efficient, stable device architectures based on materials with improved energy-level alignment, spectral response, and transport properties.
Many solar technologies use TCOs as transparent contacts. We focus on discovering and evaluating new materials, developing new processes for high performance at low cost, and directly optimizing transparent contact materials for PV conversion technologies, especially silicon, copper indium gallium diselenide (CIGS), and OPV.
We Address Industry's R&D Challenges
- New absorber, contact, and barrier materials. We develop and apply new high-performance absorber materials for improved performance and lifetime, focusing on improving photovoltage and stability to photo-oxidation.
- Better contact materials and device architectures. We are developing new or improved TCOs, including robust indium-free TCOs for PV applications. We have also demonstrated one of the first inverted organic photovoltaic devices, which are exhibiting greatly enhanced device lifetime by eliminating unstable contact and electrode materials.
- New electron/hole contact layers. We have the scientists and the tools to combine molecular design using computational resources with organic synthesis to develop new acceptors and donors to enhance device performance and lifetime.
- Mechanisms of materials and device degradation. We investigate and demonstrate new materials and device architectures that mitigate degradation, leading to improved device stability. We have developed a combinatorial degradation system that allows us to measure the lifetime of thin-film devices under light, at different substrate temperatures, with or without filters, or under different duty cycles. This system enables us to evaluate the lifetime of a large number of samples under the same or varied conditions in a parallel manner.
We Have Special Capabilities and Tools
Our resources and scientists can help you in your research areas, including thin-film deposition, high-throughput combinatorial methods, and atmospheric processing.
- A thermal evaporator housed in an inert environment that is available for metal evaporation for completing devices
- A solar simulator, external quantum efficiency unit, Kelvin probe, probe station, and impedance spectroscopy in an inert atmosphere
- Hood space for organic synthesis capabilities.
- Multi-source and radio-frequency (RF), DC, and RF+DC sputtering
- Mapping tools for composition, conductivity, work function, and optical reflectance/transmission
- X-ray diffraction (XRD) and spectroscopic ellipsometry mapping
- XRD with in situ annealing (<800°C).
We perform high-throughput combinatorial materials science. Combinatorial approaches, based on thin-film sample libraries across a range of compositions, accelerate the development and optimization of new materials for PV and other energy technology applications. Our group has developed state-of-the-art deposition, characterization, data handling, data analysis, and modeling tools to enable these high-throughput parallel approaches. Using these tools, we work closely with applications experts to rapidly develop and optimize application-specific materials.
We understand atmospheric processing. Atmospheric processing can reduce overall cost and scalability issues of PV production. Our research focuses on developing “inks” and ink-conversion processes to create desired materials with desired properties. Research is performed across all PV technologies, i.e., silicon, thin-film, and organic PV. Atmospherically processable materials developed include metals (Ag, Ni, Cu, Al), semiconductors (CuInGa[S,Se], CuZnSn[S,Se], CdTe), and oxides (ZnO, In2O3, SiOx, BaxSr1-xTiO3).
- Tabletop inkjet printer for testing inks and commercial-style inkjet printers
- Ultrasonic spray stations
- Slot coater
- Controlled-environment rapid thermal processing (RTP) systems
- Laser scribing and annealing system.
- Multi-color inkjet printing and ultrasonic spraying, aerosol jet spraying
- Integrated vacuum deposition capability
- RTP system in controlled environment
- X-ray fluorescence and X-ray diffraction analysis.
We Have Deep Expertise
Our researchers have invented and transferred various OPV and TCO technologies to industry, and we develop cells with improved performance, reliability, and cost effectiveness. One example is our work with an industry partner, HelioVolt, to develop a hybrid CIGS scheme that involved inkjet printing of precursor metal inks. The value of this approach was recognized through two awards in 2008—the Federal Laboratory Consortium Award for Excellence in Technology Transfer and an R&D 100 Award.
In addition, members of our group are key organizers and participants in industry-wide conferences, such as the Organic Photovoltaics Meeting and International Summit on OPV Stability.
We also reach beyond our group at NREL to tap into exciting work on the theoretical, experimental, and characterization focus of new materials by design. We do this by participating in the Center for Inverse Design, which is an NREL-led Energy Frontier Research Center of the DOE Office of Science. Partners include scientists from Northwestern University, Oregon State University, and Stanford University.
We Partner with Industry
- ConocoPhillips (new absorber materials for organic photovoltaic systems)
- Plextronics (contact development and lifetime of OPV)
- TDA Research (multicomponent systems for infrared absorption)
- Luna Innovations (carbon nanosheet electrodes for OPV)
- Konarka, TOTAL, Solarmer, and others.
We also collaborate in research with academic institutions such as the University of Arizona, Georgia Tech, University of California-Santa Barbara, Princeton, Stanford, University of Colorado, Colorado School of Mines, and Energy Research Centre of the Netherlands.
Working with Us
Visit Working with Us to learn more about NREL's PV partnership opportunities.