Unique PECVD machine delivered to ECN
The Roll-to-Roll PECVD (Plasma-Enhanced Chemical Vapour Deposition) machine developed by ECN, in collaboration with its German partner Roth & Rau, was delivered last spring. This pilot machine is being used to develop thin-film silicon solar cells and modules. Six metres long, it will eventually be able to provide continuous deposition of thin-film n-i-p silicon layers on hundreds of metres of steel foil, which can then be made into solar cell modules.
ECN (Energy research Centre of the Netherlands) has been working for some time now on the development of intrinsic thin-film silicon, the bulk material for thin-film silicon solar cells that collects the sunlight and converts it into electricity. To produce working cells, extremely thin layers of p- and n-doped silicon also need to be deposited as a sandwich around the thicker intrinsic silicon layer.
Delivery of the PECVD machine at the site in Petten.
The new Roll-to-Roll PECVD machine has a number of vacuum chambers where the various layers of the cell are produced one by one from silane gas. Parameters that have a major influence on deposition are deposition pressure, deposition temperature, gas flow and the relationships between the various gases and the plasma capacity.
Camile Devilee, ECN's plant manager and operator, has the following to say about the design phase of the exceptional thin-film solar cell machine: “The new system has been designed and built based on a particularly long list of machine requirements. The problems that came to light during the various acceptance tests were solved more quickly than expected, after which, following a successful final acceptance test at Roth & Rau, completion and transport to ECN were scheduled within one month.”
Adjusting and testing the PECVD machine on location.
“Following building up at ECN and the commissioning and start-up phases we have been adjusting and testing the machine as a whole”, continues Devilee. “The software built-in and supplied as standard works well. Modifications have however been made to meet ECN’s particular functional requirements, and some parameters have been changed and combined. A full cycle comprises some ten to fifty separate ‘steps’, depending on the complexity of the process. The researcher can vary the order of the various steps and the settings, so almost any conceivable deposition process can be carried out.”
ECN already has considerable knowledge and experience of an older, smaller system, which it is using wherever possible when testing the new system. The final adjustment of the PECVD machine, with parameters that can all be varied separately and independently of one another, is not expected for another six months, however, as the quality of the silicon layers has to be guaranteed, and the deposition rate needs to be set as high as possible. The primary test results are expected in November.
Sandwich technology.
The technology is complex. To deposit the working layers the machine has two separate vacuum chambers, one for the two conductive layers and one for the non-conductive layer. The two chambers have separate plasma sources because of the different requirements for the layers. The whole process of setting and adjustment has to be done for each chamber and for each of the independent layers separately. Once each of the three layers has been found suitable they can be combined. This technology enables the cost of solar cells to be reduced by a factor of three.
The ultimate aim is to set up a complete lab-scale production line for the manufacture of thin-film silicon solar panels on foil. The new machine will lie at the heart of the production line. To make this possible, research is being conducted elsewhere in the ECN Solar Energy Unit into other fabrication steps for flexible solar cells, such as laser engraving, silk-screen printing and encapsulation.
Information:
Secretariat ECN Solar Energy
Tel. +31 (0)224 – 56 47 61
solar@remove-this-part-ecn.nl
