Capacitec - PRODUCT NEWS
High Temperature CVD to Roller Gap Measurement Sensors
Chemical Vapor Deposition of TCO layer
Capacitec is supplying high temperature gap sensors to producers of Flexible Solar Cell Laminates.
In one application, a roll-to-roll production process is used in the deposition of various active and non active ultra thin layers onto the solar cell metal foil. This process offers important cost saving advantages in large scale production. There are a number of roll-to-roll steps from the deposition of the transparent top layer and the amorphous silicon layers to the final reflective metal backing.
The top transparent conductive oxide layer (TCO) is deposited by chemical vapor deposition under atmospheric pressure (APCVD) onto a temporary carrier foil. The advantage of this approach is that high deposition temperatures (up to 800°C) for the transparent conductive oxide and silicon layers facilitates deposition of high quality material at high deposition rates.
In this CVD process it is very important to set and maintain the gap between the coater head and the roll positioning the carrier foil. The coater head must also be parallel relative to the roll. If the gap is too big the coating will be too thin, too small a gap would produce TCOs that are too thick. An unparallel head would distribute the coating unevenly across the width of the substrate. The challenge in this application is that the producer cannot properly set the target gap at ambient temperature before the start of the process. This is due to the fact that, once heated during production, the roll diameter thermally expands.
To control the position of the coater head, Capacitec supplies four high temperature sensors that are positioned next to the coater head on a custom fixture that measure both the gap and parallelism between the coater head and the metal roller at production temperatures. This constant measurement ensures that the gap and parallelism are maintained during long production runs.
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