Thin-film solar cell technology is the second generation of photovoltaic (PV) solar cells, featuring a thin semiconductor going from a few nanometers to micrometers. One of the most popular types of thin-film solar technology is the Copper Indium Gallium Selenide (CIGS). CIGS solar cells have proven to deliver a high power output, are cost-efficient, feature a lower CO2 footprint, and have several other benefits.
If you are interested in learning more about CIGS solar cells, the benefits of this technology, or the current growth status of CIGS solar panels in the market, this is the right article for you.
Here you will review the basics of this technology, learn about its pros and cons, understand the different applications for CIGS solar cell technology, learn about the most recent updates on the technology, and more.
CIGS thin-film solar technology: Understanding the basics
A brief history…
CIGS solar panel technology can trace its origin back to 1953 when Hahn made the first CuInSe2 (CIS) thin-film solar cell, which was nominated as a PV material in 1974 by Bell Laboratories. In that year, researchers began to test it , and by 1976 University researchers made the first p-CuInSe2/n-CdS, taking the first steps towards CIGS thin-film solar cells. In 1995, researchers from the National Renewable Energy Laboratory (NREL) finally introduced gallium into the CIS solar cell mix, creating the first CIGS solar cell.
Basics on the CIGS solar cell structure
CIGS thin-film solar panel technology is manufactured with a p-n junction made out of Copper, Indium, and Gallium, which is later annealed with Selenide vapor. The flexible property of the module is obtained by varying the substrate, which is what gives it unique properties for different applications. The CIGS solar cell structure also features a conductive sheet for conductivity and a protective layer.
An upside of a CIGS thin-film solar panel is that its technology is extremely versatile, being able to adapt to numerous applications. PV modules using this technology can be manufactured as flexible modules, rigid modules, Building-Integrated Photovoltaics (BIPV) products, and with current technologies, even as high-efficiency bifacial modules.
Impact on the environment & recycling
There is also an important environmental advantage to CIGS thin-film solar panel technology compared to crystalline silicon (c-Si) ones. Manufacturing c-Si PV modules produce equivalent pollution of 50–60 g of CO2/kWh, while a CIGS solar panel only produces 12–20 g of CO2/kWh, which is similar to wind power that produces 10–12 g of CO2/kWh.
Since producing a CIGS thin-film solar panel requires using valuable metals, it is a good point in favor of this technology that it can be recycled. Around 100% of the silver and 85% of the Indium used to manufacture these modules can be recovered during recycling.
Great conversion efficiency & performance
CIGS solar panel technology is one of the most efficient thin-film technologies available. A record CIGS solar cell efficiency of 23.35% was achieved by Nakamura et al in 2019 for CIGS solar cells, while CIGS flexible solar panel modules feature a recorded efficiency of 22.2%, achieved in 2022 by Swiss Federal Laboratories for Materials Science & Technology (EMPA).
This technology delivers a great performance, partially thanks to its low-temperature coefficient (TCO) of only -0.36%/ºC, being excellent for all applications in extreme climate locations. As the technology is further developed or combined as tandem solar cells, it is possible to increase its efficiency.
Pros & Cons of CIGS thin-film solar panels
High conversion efficiency
The record-high conversion efficiency for CIGS solar cells has been achieved at 23.35%. This is above the average, and close to the record of other popular c-Si technologies.
Competitive production costs
CIGS solar panels have competitive production costs, thanks to their thin design, featuring a lower requirement of materials to manufacture solar cells.
Low carbon footprint
Manufacturing CIGS solar cells barely generates 12–20g of CO2 equivalent/kWh. This low carbon footprint is fairly close to that of wind energy.
Thanks to a lighter and thinner design, CIGS solar cells feature a superior aesthetic appearance. On top of it, CIGS flexible solar panel models adapt to oddly shaped buildings, ideal for improving aesthetics.
Unique properties suited for various applications
With their lightweight, CIGS solar cells can be installed on rooftops with a limited weight capacity. This technology can also be manufactured into CIGS flexible solar panel options for oddly shaped buildings or Building-Integrated Photovoltaics (BIPV).
Better performance in diffuse light & high temperatures
CIGS solar cells can perform better thanks to better adaptation in diffuse light locations and a low-temperature coefficient of -0.36%/ºC, which reduces power losses in extreme climate locations.
Suitable for bifacial applications
Bifacial CIGS solar panels can be manufactured, to take advantage of the albedo resource. The solar industry recently made breakthroughs to improve bifacial CIGS technology.
CIGS thin-film solar panels can potentially be recycled
CIGS solar cell technology can be recycled, recovering 100% of the silver and 85% of the Indium used to manufacture the cells.
Manufacturing requires a rare metal
CIGS thin-film solar panels require Indium, which is considered a rare metal. The only upside is that most of the Indium in CIGS thin-film solar panels can be recycled from old modules.
Rapid solar cell degradation in certain conditions
CIGS thin-film solar cells can be highly affected by water vapour that causes sodium migration within the cell, and increases solar cell degradation. To avoid this, it is not recommended to use this type of PV technology in areas with high humidity and intense sunlight when the product quality is unknown.
Applications of CIGS thin-film solar panels
CIGS thin-film solar panels have several applications. This technology can be used for traditional applications, but also unique ones not suitable for conventional c-Si solar panels.
Traditional residential, commercial & industrial/utility-scale applications
CIGS thin-film solar panels can be designed as rigid or flexible modules, to be used in traditional PV installations on scales that go from residential up to utility ones. The great performance in different lighting and extreme temperatures, makes these modules perform better than traditional technologies.
Building-Integrated Photovoltaics (BIPV)
BIPV is a particular application suitable for CIGS and a few other thin-film solar technologies. CIGS solar cells can be designed into the façade of a building, the windows, or adapted into different shapes to provide buildings with the capacity to produce solar power, without disrupting the aesthetics of the place.
Few technologies, including CIGS, can be adapted into space applications. Until 2023, Ascent Solar, the U.S.-based CIGS solar panel manufacturer, produced CIGS PV modules for space applications with unique properties that have been often demonstrated by NASA.
The latest findings & updates on CIGS thin-film panels (2022-2023)
Record efficiency of 22.2% for flexible CIGS solar cells
In September 2022, researchers from the Swiss Federal Laboratories for Materials Science and Technology (EMPA) presented a new record efficiency achieved for a flexible CIGS solar cell of 22.2%, at the 8th World Conference on Photovoltaic Energy Conversion (WCPEC-8). The previous record sat at 21.4%, while the record for CIGS thin-film technology, in general, is held at 23.35%.
The Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) later confirmed this achievement. The new record was achieved by modifying the composition of the CIGS layer, which increased the output voltage and improved the performance. These results can be replicated on an industrial scale to increase the efficiency of retail CIGS solar panel manufacturing.
Increased efficiency for bifacial CIGS thin-film solar cells
Researchers at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) have achieved an increased efficiency in bifacial PV modules featuring CIGS thin-film solar panel technology. The record reached an efficiency of 19.8% on the frontal side of the module and 10.9% on the rear side.
Bifacial technology is great for applications that take advantage of the albedo resource, but a higher efficiency is particularly interesting in thin-film solar technology because of the transparent properties of the module. This achievement could also lead to increased efficiencies in applications like BIPV.
Researchers designed a perovskite-CIGS tandem solar cell that could achieve a 29.7% efficiency
Research of tandem solar cells featuring perovskite has shown potential in publications over the years. In 2023, researchers at the Chitkara University in India published a paper in Energy Fuels illustrating a numerical study that shows an enhanced tandem CIGS-perovskite solar cell, demonstrating that a solar conversion efficiency of 29.7% can be achieved.
The study is based on a monolithic tandem solar cell featuring a top perovskite layer featuring a wide band gap (Eg) of 1.68 eV and a CIGS layer with a 1.1 eV Eg. There are still some limitations from losses and interferences that might not have been considered, but the potential of this calculation could yield impressive results in experiments performed in a laboratory looking to reproduce the design.
Japanese researchers create a roadmap to increase efficiency for CIGS thin-film solar panels
Currently, the average CIGS thin-film solar panel features a conversion efficiency that slightly surpasses 18%. In October 2022, Japanese researchers from the National Institute of Advanced Industrial Science and Technology (AIST) published a paper proposing a methodology to increase the efficiency of a CIGS solar panel beyond the 20% solar conversion efficiency threshold.
The paper promotes the acquisition of solar energy by creating a roadmap towards high-efficiency thin-film CIGS flexible solar panel models that can be used in curved surfaces and rooftops with weight restrictions. The method recommends reducing CIGS deterioration at the edge of solar cells by using appropriate passivation/termination treatments during manufacturing or by replacing mechanical scribing.
How do CIGS thin-film solar panels compare to other technologies in the market?
In the solar industry, there are many outstanding PV technologies available. In this section, we compare CIGS thin-film solar panel technology against Passivated Emitter Rear Cell (PERC) technology, which holds the highest market share, and against Tunnel Oxide Passivated Contact (TOPCon) technology, an upgraded version of PERC technology with rising in popularity.
|Highest Recorded Efficiency
|Traditional rigid PV module applications
Popular c-Si technologies like PERC and TOPCon have surpassed CIGS solar panel technology in a few metrics, but this thin-film technology is still highly capable of competing with them.
The highest recorded efficiency for CIGS solar cells is a few points below that of TOPCon, and only slightly below that of PERC technology. While mass production modules can go a little above 18%, Japanese researchers are already working on increasing that efficiency beyond the 20% threshold.
A great point in favor of CIGS thin-film solar panels is their temperature coefficient. TOPCon is the best-performing technology, but CIGS performs better in extreme climates than PERC technology and also performs exceptionally in diffuse light conditions.
The strongest point in favor of CIGS thin-film solar panel technology is the high number of applications that surpass PERC and TOPCon PV technologies. CIGS solar panels can be used as traditional rigid modules, as flexible PV modules to install in curved roofs or odd-shaped buildings, and for many other applications.
The light weight of CIGS solar panels is great for applications where there is a maximum weight limit. The weight for PERC and TOPCon PV modules can go anywhere from 18 kg up to 33 kg, but some CIGS thin-film solar panels barely weigh around 5 kg. This makes them an excellent option for homes with roof weight limitations to enjoy solar energy without changing the roof.
On top of the flexible and rigid PV applications, CIGS thin-film solar technology can be designed and manufactured for BIPV applications. CIGS PV modules can be produced in various colors and patterns, created in custom shapes for aesthetic applications, or used as PV façades, solar glass windows, shingles, and more.
CIGS thin-film solar panels & its market: An overview into the future
CIGS thin-film solar panels currently hold only 1% of the market share, but the technology has been constantly growing in the solar industry since 2017, making it one of the most important thin-film solar technologies. It is expected that CIGS thin-film solar panel technology will keep on growing at a compound annual growth rate (CAGR) of 6.97% from 2019 to 2027.
Currently, there are several CIGS solar panel manufacturers. These include the Switzerland-based company Flisom with a 15 MW production line, Sunflare with a 40 MW production capacity, and several others, including the French startup known as Solar Cloth, which recently started with a 20 MW production capacity.
Another important aspect to consider when talking about the future of CIGS thin-film solar panel technology is the number of projects that aim to improve this technology.
CIGS-perovskite tandem solar cells
A promising development involving CIGS solar cells is the creation of the CIGS-perovskite tandem solar cells. The technology provides great opportunities for the future solar industry since it has proven a solar conversion efficiency of over 24%, featuring lightweight, flexibility, and resistance to radiation.
High-performance CIGS solar cells
Another promising project is the development of high-performing CIGS solar cells using an improved synthesis method. The UL-Flex-Cell project ended in February 2023, featuring a budget close to €160,000, and was coordinated by the International Iberian Nanotechnology Laboratory. The project aimed to improve the manufacturing of the CIGS solar cell to increase the efficiency of the modules.
Applying silicon solar cell technology to CIGS solar cells
There is a PV technology improvement project aimed to combine c-Si solar cell technology with CIGS solar cells, increasing solar cell efficiency to 23%–26%, improving stability and reliability, and reducing costs. The project was hosted by the Interuniversitair Micro-Electronica Centrum (IMEC), featured a budget of a little under €2,000,000, and ended in the Q3 of 2022. The results are published in 33 peer-reviewed articles, 1 monographic book, and 1 proceeding conference.
Finally, in Q3 of 2022, it was announced the Project NovaCell that is hosted by the NOA Research Group. This project aims to develop a novel architecture for CIGS solar cells. They plan to achieve this by reducing the thickness of the solar cell to 700 nm, saving materials, while still achieving a 16% CIGS solar cell efficiency at a low cost.