The U.S. government’s Solar Energy Technologies Office (SETO). Department of Energy funds research and development initiatives aimed at extending the lifespan and efficiency of hybrid organic-inorganic perovskite solar cells, accelerating the commercialization of perovskite solar technologies, and lowering manufacturing costs.
Perovskite solar cells: what are they?
A family of materials known as halide perovskites has demonstrated potential for solar cells with great performance and low production costs. Although various varieties of non-halide perovskites (such as oxides and nitrides) are used in other energy technologies, such as fuel cells and catalysts, the word “perovskite” derives from the nickname for its crystal structure.
The efficiency of perovskite solar cells has increased dramatically over the past few years, rising from reports of around 3% in 2009 to over 25% now. Even though perovskite solar cells have rapidly increased their efficiency, a number of obstacles must yet be overcome before they can be considered a viable commercial technology.
To make perovskite technologies commercially viable, SETO has identified four key issues that must be resolved at once. Each task has its own set of obstacles and must be overcome in order to meet certain technical and financial goals. Through a number of financial initiatives, such as the SETO FY2021 Small Innovative Projects in Solar (SIPS), SETO 2020 Photovoltaics, and SETO FY20 Perovskite funding programs, as well as the Perovskite Startup Prize, the office is assisting initiatives that aim to address these issues.
STABILITY AND PERMANENCE
In comparison to the most popular photovoltaic (PV) technologies, perovskite solar cells have shown comparable power conversion efficiencies (PCE) with the potential for improved performance. When perovskites react with moisture and oxygen or are exposed for a lengthy period of time to light, heat, or electrical current, they can degrade. Researchers are investigating degradation in both the perovskite material itself and the surrounding device layers to boost stability. In order to create commercial perovskite solar products, cell endurance must be improved.
Perovskite solar cells are currently not commercially practical due to their short operational lifetimes, despite substantial advancements in our understanding of the stability and degradation of these materials. Even though commercial applications outside of the power sector would be able to endure a shorter operational life, they would still need to make improvements in areas like device stability while being stored. Regardless of other advantages, technologies that cannot function for more than 20 years are unlikely to succeed for commercial solar power generation.
EFFICIENT POVER CONVERSION A LARGE SCALE
Perovskite PV cells have improved quickly during the past five years, surpassing nearly all thin-film technologies in small-area lab devices (excluding III-V technologies) in terms of power conversion efficiency. High-efficiency devices, however, have not always been reliable or scalable to produce. Perovskites must retain these high efficiencies and achieve stability in large-area modules in order to be widely deployed. The mobile, emergency response, or operational energy markets—where lightweight, high-power devices are essential—might benefit from continued progress in medium-area module efficiency.
By altering the material composition, perovskites can be tailored to respond to various sun spectrum hues, and numerous formulations have shown excellent performance. Due to their versatility, perovskites can be coupled with other, differently tuned absorber materials to increase the output of a given device. A tandem device architecture is what this is. Tandem devices can potentially have power conversion efficiency beyond 33%, which is the theoretical cap for a single junction PV cell, by utilizing multiple PV materials. Perovskite materials make ideal hybrid-tandem partners because they can be tailored to take use of the sections of the solar spectrum that silicon PV materials can’t use very effectively. A perovskite-perovskite tandem can also be created by joining two perovskite solar cells with various compositions. Due to their high power-to-weight ratios and flexibility, perovskite-perovskite tandems could be particularly competitive in the mobility, emergency response, and defense operations sectors.
For perovskite solar cells to be produced commercially, perovskite manufacturing needs to be scaled up. Scalability and reproducibility of the methods could boost production and enable perovskite PV modules to reach or surpass SETO’s levelized cost of energy goals for PV.
The layers of materials used to construct perovskite solar cells are either printed, coated with liquid inks, or vacuum-deposited. It is challenging to produce homogenous, high-performance perovskite material on a wide scale, because the efficiency of big-area modules and small-area cells differ significantly. The solution to this problem, which is still a hot topic of research in the PV field, will determine the direction of perovskite manufacture in the future.
There are considerable attempts being made to apply scalable methodologies to perovskite production, yet many of these processes utilized to create lab-size perovskite devices are difficult to scale up. There are two main forms of production for thin-film technologies:
- Sheet-to-Sheet: The device layers are applied on top of a rigid base, which commonly serves as the front surface of the finished solar module. This method is frequently applied in the cadmium telluride (CdTe) thin-film sector.
- Roll-to-Roll: Device layers are deposited on a flexible foundation that is later employed as either the interior or exterior of the finished module. The performance constraints of these technologies prevented roll-to-roll processing from taking off commercially, despite researches’ attempts with other PV technologies. However, it is frequently utilized to make paper goods like newspapers as well as photographic and chemical film.
Perovskites offer the potential for more rapid capacity increase than silicon PV if these scalable production methods can be used to produce them consistently. Both of these procedures are well-established in other industries, so scaling costs and risk can be further decreased by utilizing existing knowledge and supply chains.
The potential environmental effects of perovskite materials, which are predominantly based on lead, are additional obstacles to commercialisation. In order to assess, lessen, alleviate, and possibly completely eliminate toxicity and environmental concerns, alternative materials are being researched.
VALIDATION OF TECHNOLOGY AND BANKABILITY
The commercialization of perovskite technology depends on validation, performance verification, and bankability—the ability of financial institutions to finance a project or proposal at fair interest rates. Lack of appropriate field data and variations in testing procedures have made it difficult to compare performance across perovskite devices and predict long-term operating behavior.
The current standard PV technologies were used to design the testing procedures for solar PV devices. These test silicon and CdTe solar cells, which degrade very differently from perovskite technology, indoors using techniques that could also reliably forecast their performance outdoors. Confidence in perovskite technologies must be increased in order to encourage investment in production scale-up and deployment. This requires objective, trusted validation utilizing test methods that can sufficiently screen for real-world failure mechanisms. This standardized validation is particularly difficult and crucial since perovskite solar cells have continually evolving material and device compositions.
To address these issues, SETO has provided funding for the Perovskite Photovoltaic Accelerator for Commercializing Technologies (PACT) Validation and Bankability Center. To increase our knowledge and trust in the long-term viability of perovskite PV technologies, PACT will carry out field and lab testing, design and validate accelerated test methods, and energy yield models, as well as carry out technical and commercial bankability studies.
Based on the Performance Targets for Perovskite Photovoltaic Research, Development, and Demonstration Programs Request for Information, SETO has also created performance targets to assist commercialization paths for perovskite PV (RFI). These goals for perovskite PV device efficiency, stability, and replication can help research directions and goals align, ensuring that future funding programs are pertinent and advancing the commercialization and de-risking of perovskite technology.
The Perovskite Solar Cell Ratings