Roll-To-Roll Solar Cell Building Technology Advances: Cost-Effective PV Solutions For Manufacturers

Outline Part 3

Introduction
The State of Solar
Roll-to-Roll Production
Optimation’s Capabilities

“Solar energy is bound to be in our future. There’s a kind of inevitability about it.” -Jim Inhofe

We may not know what the future has for us, but one thing is certain, solar is the present and the future. Solar panels are now so accessible that even homeowners can purchase a solar LED street lamp to light their porch with no extensive knowledge or experience. This is what we call practical innovation. Solar technologies are now commonly used for vehicles, homes, industrial power sourcing, and many more within all residential, commercial, and industrial range. The conversion of sunlight to electrical energy through photovoltaic (PV) panels can be stored in batteries or thermal storages.

Despite the general acknowledgement, tackling renewable energy challenges is easier said than done. Within the renewable energy industry itself, provision of solutions to different products require different solar cell techniques and building methods to integrate seamlessly.

Solving problems, testing new process techniques, evaluating efficiencies and alternatives, as well characterizing, quantifying, and successfully implementing capital projects require more than an extensive knowledge and a couple of engineers in hand.

Most importantly, you need to have a team that is on top of trends and proven innovations.

If you’re looking to access project resources, Re:Build Optimation’s industrial resources include a two hundred engineers and industrial trades workers, and 140,000 feet of fabrication space which includes a development lab for wide web conveyance research. Re:Build Optimation has proven success in facilitating the use of leading-edge technology with unique ability to provide design and fabrication services from conceptual stage of a product/process, through prototyping and full production scale operation. This expertise is especially important if solar cells are to be manufactured by high speed coating of the electro voltaic materials on a glass substrates.

If you work anywhere near or in a manufacturing or production line, this article will be a good resource for you by giving a general, yet specific overview on the Roll-to-Roll Technology and how it helps solar cell manufacturing processes. This technique is paving the way to a superior and cost-effective solar technology.

The State of Solar

Due to the very extensive process of solar panel manufacturing, it is well known that only a selected number of manufacturers control the whole value chain from raw to ready material of solar cells. Solar PV modules focus more on the assembly of the solar cells from different suppliers while the manufacturing process for the solar cell itself is in a whole different line. Typically an individual PV cell produces about 1-2 watts of power, made of different semiconductor materials. To withstand the outdoor environment, the cells are coated with protective materials in a glass and/or plastic combination.

Solar cell is the smallest, most basic, building component that generates electricity in a solar panel. Different types of solar cells have different levels of efficiency and capability of converting solar energy to electricity.

Along with the range of steps that it takes to produce solar cells from raw quartz are commonly three structures of solar cell production in the supply chain.

Quartz -> Solar Cells
Quartz -> Silicon Wafers
Silicon Wafers -> Solar Cells

The first structure focuses on the entire value chain while the second and third works on providing different stages of the solar cell production itself.

PV modules and arrays are just one part of a PV system, where further down the line, the system itself includes mounting structures for sun-exposure angle, as well as components that take the direct-current (DC) electricity produced by modules and convert it to the alternating-current (AC) electricity.

The modular structure can be built to meet any size of electrical power needs.

Roll-to-Roll Solar Cell Production Processing

The Roll-to-roll processing for production of solar cells is a developing technology which promises to dramatically reduce the cost of traditional semiconductor manufacturing methods.

To start the production process, silicon recovery and purification is done, followed by the development of silicon wafers by slicing the purified product into utilizable disks. The silicon wafers will then be further processed into ready-to-assemble solar cells.

Perovskite solar cells have also been considered a better alternative than silicon with better high-energy blue photons absorbing ability from sunlight due to its crystallographic structure.

A perovskite has the same crystal structure as calcium titanium oxide (CaTiO₃), with lead as its dominant metal. It is considered thin-film tech without silicon components.

Perovskite solar cells (PSCs) photo-absorber features have superior advantages such as high defect tolerance, high efficiency, cost-effective fabrication, band gap tunability and long carrier diffusion length. This explains why perovskite solar cell development has increased significantly over the last decades, especially since lead is an inexpensive material.

PSCs are built with different materials than traditional silicon wafers and have the advantage of simple processing while traditional silicon is known to require expensive multistep processes with intensive temperature and vacuum facility.

Researchers have also investigated increased performance in tandem, silicon-perovskite stacked cells are said to push power converting efficiency by 30%.

There are different methods and techniques for PSC manufacturing from lab-to-fab, to mention a few, includes:

Drop casting
Spray coating/Spin coating
Ultrasonic spray coating
Slot die coating
Electrodeposition
CVD
Thermal vapor deposition
Vacuum deposition
Screen printing
Ink-jet printing

Perovskite has been proved to be a feasible solution and process for solar panel manufacturing, however a new strategy called Polymer has also been adopted to result in an even more efficient, stable, and hysteresis-reduced PSCs. Although scalable fabrication is still a big challenge in the value chain, successful commercialization is no longer far out of reach with roll-to-roll (R2R) processing.

Building a semiconductor fabrication facility is usually very expensive with around $15 billion of estimated R&D cost. The goal or purpose of the semiconductor manufacturing facility is to develop and set out a series of nanofabrication processes that will perform on the surface of substrate for crystal silicon purification.

The six main semiconductor manufacturing steps for a basic technology method includes:

Deposition
Photoresist
Lithography
Etch
Ionization
Packaging

Roll-to-roll (R2R) processing is also known as web processing or reel-to-reel processing. It’s a substrate-based manufacturing process in which additive and subtractive processes are used to build structures in a continuous manner.

Re:Build Optimation’s media conveyance facility (MCF), along with its web coating, handling and converting experience, provides clients with an ideal development and prototyping partner. They can work with clients to design and implement large scale, low cost, manufacturing facilities for solar energy products.

R2R process enables high-throughput and low-cost production to the flexible and light-weight PSCs.

There are three key steps to the R2R deposition of PSCs layers:

Precursor deposition (Scalable coating process)
Phase conversion (Antisolvent bathing)
Crystallization (Thermal annealing)

R2R processing is generally a fabrication method that embeds, coats, prints, or laminates, using several rollers known as the web path. The technique is used in manufacturing, winding the substrate material over and through the rollers as it is applied. Through additive and subtractive materials on the substrate, the variable then moves along the web to finally create a product or assembling part (reel-to-reel).

A substrate originates from a web made of flexible, thin, and long material which are then stored or transported as rolls for the R2R processing stage. These materials may comprise plastic films, textiles, paper, foils, metals, as well nanomaterials.

The reason R2R processing technology is much more cost-efficient than other methods is because the processing is continuous, resulting in a far higher-speed production and no start-stop issues in regards to the sheet processing. In fact, the R2R process can produce rolls in mass amounts of output at high production rate, efficiently, and cost-effectively.

Not only in renewable energy or solar cell manufacturing, the R2R processing is also currently utilized worldwide in various manufacturing and industrial sectors such as computing, textiles, medical, biosciences, metal fabrication, IT, energy and many more.

To achieve maximum potential result, a major factor and dependent variable for the effectiveness of R2R processing is web tension control of the substrate web as it moves from roll-to-roll. A constant and uniform tension must be maintained to produce effectively. Any minor hindrance or disrupting variable in tension may destabilize the material applied to the substrate causing defective or failed products/parts. Possible effects may be de-lamination, short circuiting, wrinkling, cracks or low fine line resolution.

Re:Build Optimation’s Capabilities

To produce the best quality parts/products with R2R technology, media conveyance capabilities are crucial and important, especially if the substrate to be coated is glass. Re:Build Optimation has proven media conveyance capabilities with nearly forty years of proven industrial experience.

Solar companies around the world have demonstrated industrially-applicable R2R processing with perovskite. Perovskite can be processed into thin, light-weight and potentially semitransparent modules to integrate with windows or curved elements.

A case study based on a solar R&D organization in Germany have proven an astounding efficiency result as seen below:

“The in-line roll-to-roll coating, drying and annealing processes were executed at a linear speed of 5 m/min on a 30-cm wide commercial PET/ITO foil and under ambient conditions. After applying a newly developed off-line single device finishing step, individual solar cells of 0.1cm2 achieved efficiencies of up to 12,6%, measured under maximum power point tracking conditions during 5 minutes. All process steps on this roll-to-roll line were performed using low cost materials whilst keeping the process temperatures below 120 ⁰C. This shows the high volume production potential of this new emerging thin film PV technology.“

This demonstration of 5m/min for perovskite layered solar cells shows high-volume production at an expected low cost and efficiency of up to 15%.

The current world record efficiency of a small lab scale perovskite-based PV cell is 22,1%.

Re:Build Optimation has long been engaged in the support of carbon neutral and renewable energy projects and processes. Projects have been in support of research universities, start-ups, and large commercial companies. Design is done with a broad range of process and mechanical engineering and manufacture using exotic materials and precision equipment with proven success in facilitating the use of leading-edge technologies.

Clients have a single source for seamless, cost-effective, and timely completion of their renewable projects.

Not only in solar cell productions, Re:Build Optimation also has proven tracks in biofuels, ethanol, and jet fuel, hydrogen, methanol, green plastics, wind turbines, plant and food preservation, as well as batteries and storage systems.

With R2R processes, Re:Build Optimation designed and fabricated lithium battery assembly and test systems as well designed manufacturing systems for anode and cathodes manufacturing on high speed roll-to-roll processes.

Re:Build Optimation also provides flexible web property precision measurement for R2R manufacturers. This important product data is then utilized in a predictive analysis and modeling to ensure robust and reliable web handling processes and performance.

Suitable for engineers and technicians at all levels, Re:Build Optimation’s mechanical measurements services of key web properties will ensure that the product has been designed properly for web handling compatibility in the conveyance and processing machinery.

With a wide selection of measurement capability, Re:Build Optimation measurement capabilities include:

Web/Roller and Web/Web Capstan and Sled Friction
Tensile Properties Including Young’s Modulus
Stack Modulus
Web and Roller Surface Roughness
Nip System Diagnostics

The innovative state of solar cell manufacturing is still an ongoing and evolution in the making. However, as engineers, our job is to provide the most proven, successful, and valuable technology man can make today to achieve even more greatness than today.

You can start your success journey now with the right team and resource to help you with your industrial applications… Concept to Completion by contacting us today.

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