Helianthos
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Helianthos is a program focused on the development of solar cell modules that can be manufactured via roll-to-roll processes on long foil substrates. Helianthos is being carried out by a core group of industrial partners and is supported by universities, technology institutes, and other partners.
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[edit] Process Technology
The development relies on the use of a temporary substrate on which flexible thin film solar cells are deposited. The use of the temporary substrate allows to use relatively high processing temperatures while using (semi-)continuous roll-to-roll (or reel-to-reel) production processes and cost-efficient abundantly available materials.
The active layers of such solar cells comprise a transparent conductive oxide layer (TCO) and active absorber layer (e.g. thin film silicon) and a back contact layer (e.g. a reflective metal layer).
[edit] Process Sequence
The key steps in the process sequence are:
- Deposit the TCO layer on a temporary metal substrate foil using chemical vapor deposition (CVD) at about 500 °C (932 °F) .
- Deposit the active absorber layer (e.g. thin film silicon layer) using plasma enhanced CVD
- Deposit the reflective back contact by means of physical vapor deposition
- Pattern for monolithic interconnection
- Laminate to permanent carrier foil
- Remove the temporary substrate foil by means of wet etching
- Confectioning, contact application and encapsulation
[edit] Applications
Using this process flexible photovoltaic (PV) laminates will be fabricated that substantially reduce the kWh costs of solar electricity. Further, the resulting photovoltaic laminates are lightweight, unbreakable, aesthethic and offer freedom of design.
PV laminates have the potential to be used for a range of applications, including: - Large area roofing and other large area applications to generate electricity - Rural electrification - Industrial applications, and - Consumer applications, e.g. solar cells for portable applications.
