Final Report Summary - SOLARPLAS (Development of Plasma-Chemical Equipment for Cost-Effective Manufacturing in Photovoltaics)
Targeting at an integrated concept for in-line production of solar cells, the introduction of atmospheric pressure plasma processes is a promising alternative route toward establishing cost-efficient production technologies. APP processing is expected to lead to reduced running costs because of reduced chemical waste (e.g. avoid NOx emissions from acidic etch) and reduced handling operation due to in-line processing. Furthermore, the technology can be applied for future very thin solar wafers which substantially save raw material usage but cannot be processed with conventional wet chemistry because of increased wafer break rate. High demands concerning throughput require equipment for large area processing with high etch rate. The technology has the potential to be implemented into different processing steps such as saw damage removal, reduction of front side reflection losses by both surface texturing and anti-reflection layers, PSG removal, edge isolation, etc.
The following are the exploitable results resulting from the SOLARPLAS project:
1. Surface texturisation by plasma etching at atmospheric pressure
A well defined silicon surface structure, resulting from texture etching, leads to an improved light coupling into the solar cell and hence an improved cell efficiency.
2. Rear emitter plasma etching at atmospheric pressure
After phosphorus doping the wafer is completely covered by the emitter like a conductive shell, which leads to a short circuit between front and back of the cell.
3. Plasma chemical etching of PSG at atmospheric pressure
Phosphorus silicate glass (PSG) is formed on the wafer surface during emitter diffusion. Plasma etching of PSG represents a very challenging process step, because it has to show a high rate without damaging the underlying emitter layer (a high etch selectivity).
4. PECVD of silicon nitride at atmospheric pressure
Amorphous hydrogenated silicon nitride layers applied on the front surface of solar cells serve as anti-reflecting coating and provide surface and bulk passivation.
5. SiO2 barrier layer on polymer foil
Coatings on polymer web substantially widens out the potential use of these materials. Examples for potential applications comprising a high added value are scratch resistant surfaces, gas or aroma barrier, and anti-fog layers. A low temperature atmospheric pressure plasma process for roll-to-roll treatment of polymer foils is a solvent free and cost effective solution.
6. Electrical equipment for long arc plasma under atmospheric pressure
For a stable and reliable operation of the linear extended DC arc plasma source used for the ArcJet-technology a sophisticated power supply module is necessary. Therefore, a completely new TopCon power supply system split up into 2 modules 64 kW DC each with improved liquid cooling system and a CANopen control bus architecture was developed.
In terms of technical implementation, the system has reached an industrial degree of maturity and is ready to be introduced to an end-user level.
The following are the exploitable results resulting from the SOLARPLAS project:
1. Surface texturisation by plasma etching at atmospheric pressure
A well defined silicon surface structure, resulting from texture etching, leads to an improved light coupling into the solar cell and hence an improved cell efficiency.
2. Rear emitter plasma etching at atmospheric pressure
After phosphorus doping the wafer is completely covered by the emitter like a conductive shell, which leads to a short circuit between front and back of the cell.
3. Plasma chemical etching of PSG at atmospheric pressure
Phosphorus silicate glass (PSG) is formed on the wafer surface during emitter diffusion. Plasma etching of PSG represents a very challenging process step, because it has to show a high rate without damaging the underlying emitter layer (a high etch selectivity).
4. PECVD of silicon nitride at atmospheric pressure
Amorphous hydrogenated silicon nitride layers applied on the front surface of solar cells serve as anti-reflecting coating and provide surface and bulk passivation.
5. SiO2 barrier layer on polymer foil
Coatings on polymer web substantially widens out the potential use of these materials. Examples for potential applications comprising a high added value are scratch resistant surfaces, gas or aroma barrier, and anti-fog layers. A low temperature atmospheric pressure plasma process for roll-to-roll treatment of polymer foils is a solvent free and cost effective solution.
6. Electrical equipment for long arc plasma under atmospheric pressure
For a stable and reliable operation of the linear extended DC arc plasma source used for the ArcJet-technology a sophisticated power supply module is necessary. Therefore, a completely new TopCon power supply system split up into 2 modules 64 kW DC each with improved liquid cooling system and a CANopen control bus architecture was developed.
In terms of technical implementation, the system has reached an industrial degree of maturity and is ready to be introduced to an end-user level.
