Frequently Asked Questions
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What is Closed Space Sublimation (CSS)?
Closed Space Sublimation (CSS) is an advanced thin-film deposition method used for producing CdTe, perovskite, and other solar absorber layers. By heating a solid source material in a low-pressure vacuum, CSS allows vaporised atoms to deposit onto a nearby substrate, forming dense, uniform coatings with high efficiency and material utilisation, ideal for all types of thin-film solar modules.
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How does the Closed Space Sublimation (CSS) coating process work?
In CSS, the source and substrate are placed in close proximity, typically a few millimeters apart, within a controlled low-pressure chamber. The source material, such as CdTe or perovskite, is heated to a sublimation point where it transitions from solid to vapor. The vapor then travels a short distance through inert or reactive gas before condensing on a cooler substrate to form a crystalline thin film. By controlling temperature gradients, gas composition, and deposition distance, the process achieves excellent film uniformity within ±2 percent and high deposition rates up to one micrometer per minute.
1) Heating: CdTe or perovskite source material is sublimated (solid to vapour).
2) Transport: Vapor travels a short distance through an inert or reactive gas.
3) Deposition: Material condenses on the cooler substrate, forming a crystalline thin film. By adjusting temperature gradients and gas composition, CSS achieves excellent film uniformity (±2 %) and high deposition rates (~1 µm/min).
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Why is Closed Space Sublimation (CSS) used for solar cell manufacturing?
CSS coating technology is preferred in solar cell manufacturing for its high throughput, excellent film density, and superior adhesion. It delivers particle-free coatings for clean absorber layers and ensures stable module performance and long-term reliability. The system’s high material efficiency and low contamination make it a cost-effective solution for industrial-scale solar production, where yield and uniformity are critical to achieving maximum conversion efficiency.
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What materials can Closed Space Sublimation (CSS) deposit?
NTI Nanofilm’s CSS system supports a wide range of semiconductors and oxide materials, including CdTe (Cadmium Telluride) absorber films, perovskite compounds for tandem solar cells, CdS, ZnTe, ZnO window and buffer layers, and transparent conductive oxides (TCOs) for photovoltaic interfaces. These films are essential for solar PV modules, optoelectronic components, and energy devices that demand uniform, high-purity coatings.
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What advantages does Closed Space Sublimation (CSS) have over sputtering or CVD?
Compared with PVD sputtering or CVD coating, CSS offers simpler chamber design, fewer plasma-related defects, higher material utilization above 90 percent, and rapid deposition rates with consistent stoichiometry and density control. Its scalable inline system enables high-throughput solar manufacturing while maintaining superior film quality, making CSS a preferred technology for cost-efficient thin-film solar production..
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What are NTI Nanofilm’s Closed Space Sublimation (CSS) system features?
Inline CSS System developed by NTI Nanofilm integrates modular chambers for sublimation, deposition, and annealing, with SUS304 vacuum construction for durability and stability. It offers precise temperature control, heating the source up to 700°C and maintaining substrate temperatures around 600°C for optimal film crystallization. With a large coating range of 1200 mm and custom gas control for Ar, O₂, and N₂, the system supports continuous inline coating of full-sized solar panels at a rate of up to one panel per minute, ensuring uniform coating thickness and reproducible results across industrial production scales..
