High Rate Deposition of High Pure Silicon Thin Films for PV-Absorber Layers by Crucible-Free Electron Beam Physical Vapor Deposition
(Room Room 104-A)
29 Apr 19
3:20 PM
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3:40 PM
Tracks:
Coatings for Energy Conversion and Related Processes
Crystalline silicon thin film technology becomes attracting progressively for commercialization, because of its enhancing solar cell performance and cost-effectivity. The fabrication of photovoltaic absorber layers requires an economic method for depositing silicon thin films of several micrometer thickness and excellent layer properties such as high purity, layer thickness homogeneity and low layer stress. To fulfill these challenges the crucible-free electron beam physical vapor deposition (EB-PVD) is a predestinated technique, because it offers the highest deposition rates and EB-PVD is well established in industries. For crucible-free EB-PVD, high-purity silicon evaporation material is arranged in a special manner for avoiding direct contact to any contaminating material such as from the crucible. Deflecting the EB on materials top face the silicon melts locally and evaporates. Heating up and cooling down the brittle material without cracking and avoiding spilling out of the melt are critical aspects for the crucible-free evaporation method. The feasibility of crucible-free EB-PVD was demonstrated successfully in experiments with different configurations of evaporation material. Deposition rates above 500 nm/s have been reached. By using a double-ingot arrangement and superposing vapor from multiple sources the relative deviation of layer thickness could be reduced to < ±5 % on a substrate width of 200 mm.