Roll-to-roll processing

In the field of electronic devices, Roll-to-roll processing, also known as web processing, reel-to-reel processing or R2R, is the process of creating electronic devices on a roll of flexible plastic or metal foil. In other fields predating this use, it can refer to any process of applying coatings, printing, or performing other processes starting with a roll of a flexible material and re-reeling after the process to create an output roll. These processes can be grouped together under the general term converting. Once the rolls of material have been coated, laminated or printed they are normally slit to their finished size on a slitter rewinder.

R2R in electronic devices

Large circuits made with thin-film transistors and other devices can be easily patterned onto these large substrates, which can be up to a few metres wide and 50 km long. Some of the devices can be patterned directly, much like an inkjet printer deposits ink. For most semiconductors, however, the devices must be patterned using photolithography techniques.

Roll-to-roll processing is a technology that is still in development. If semiconductor devices can be fabricated in this way on large substrates, many devices could be fabricated at a fraction of the cost of traditional semiconductor manufacturing methods. Most notable would be solar cells, which are still prohibitively expensive for most markets due to the high cost per unit area of traditional bulk (mono- or polycrystalline) silicon manufacturing. Other applications could arise which take advantage of the flexible nature of the substrates, such as electronics embedded into clothing, large-area flexible displays, and roll-up portable displays.

Thin-film cells

A crucial issue for a roll-to-roll thin-film cell production system is the deposition rate of the microcrystalline layer, and this can be tackled using four approaches:

• very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD)
• microwave (MW)-PECVD
• hot wire chemical vapour deposition (hot-wire CVD).
• the use of ultrasonic nozzles in an in-line process

See also

• Amorphous silicon
• Low cost solar cell
• Printed electronics
• Roll-to-roll electronics inkjet printer
• Thin film solar cell
• Roll Slitting