Continuous CdTe Vapor Deposition for Photovoltaic Modules
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Solution Overview
Problem
Current thin film deposition processes for CdTe photovoltaic modules are inefficient and costly due to non-uniformity, material waste, and limitations in processing large substrates, particularly in the batch-based Close Space Sublimation (CSS) system which interrupts the deposition process for replenishing CdTe source and handling substrates.
Innovation Solution
A modular system and process for continuous vapor deposition of a thin film layer on photovoltaic substrates, utilizing a vacuum chamber with pre-heat, vapor deposition, and cool-down sections, and a conveyor system for continuous substrate conveyance at a controlled rate, with a feed system to supply CdTe source material without interruption, ensuring uniform film thickness and minimizing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If batch-based CSS process is used, then film deposition can be completed, but the process must be periodically interrupted to replenish CdTe source, reducing productivity
Solution Approach 1:
The patent implements a continuous vapor deposition process where substrates are conveyed through a deposition chamber without stopping the CdTe source replenishment. The feed system continuously supplies sublimed CdTe material to the substrate surface during conveyance, eliminating batch interruptions and maintaining continuous productive action.
Solution Approach 2:
The patent pre-sublimes CdTe source material and maintains it in vapor phase within the deposition chamber before substrates arrive. This preliminary preparation of the vaporized CdTe source ensures immediate deposition capability when substrates are introduced, eliminating waiting time and maintaining continuous process flow.
2Manufacturing precision
If substrates are indexed into vapor deposition chamber for batch processing, then film can be deposited, but significant CdTe material is wasted during indexing and positioning steps
Solution Approach 1:
The continuous conveyance process eliminates idle periods where CdTe material would sublime without depositing onto substrates. Substrates move continuously through the deposition zone, ensuring that vaporized CdTe material is consistently captured on substrate surfaces rather than being lost during positioning or indexing operations.
Solution Approach 2:
The system design allows the vapor deposition process to automatically continue during substrate conveyance without requiring manual intervention or process interruption. The CdTe source replenishment and substrate processing occur simultaneously through the continuous feed system, making the process self-sustaining and eliminating material waste associated with manual batch operations.
3Manufacturing precision
If batch processing is used with finite deposition time, then film layer is formed, but the process cannot be readily stopped and restarted, causing non-utilization of CdTe material
Solution Approach 1:
The continuous vapor deposition process maintains steady-state operation with constant substrate conveyance and continuous CdTe source replenishment. This eliminates the need to stop and restart the deposition process, ensuring that energy invested in heating and vaporizing CdTe material is continuously utilized for productive film formation rather than being wasted during process interruptions.
Solution Approach 2:
The system employs dynamic control of substrate conveyance speed and CdTe feed rate to maintain optimal deposition conditions throughout continuous operation. This dynamic adjustment allows the process to adapt to varying production requirements while maintaining continuous operation, preventing the energy waste associated with frequent start-stop cycles.
4Ease of manufacture
If CSS system processes relatively small surface area substrates, then batch processing is feasible, but large scale production of large substrates is economically unsustainable
Solution Approach 1:
The patent transitions from processing substrates in a batch manner (one at a time or in small groups) to continuous conveyance through the deposition chamber. This dimensional change in the processing approach allows large substrates to be processed continuously at high throughput, making large-scale production economically viable while maintaining process control.
Solution Approach 2:
The deposition chamber and conveyance system are divided into functional zones (source replenishment zone, deposition zone, cooling zone) that operate simultaneously. This segmentation allows different operations to occur in parallel, enabling continuous processing of large substrates while maintaining the simplicity of individual process steps within each zone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient, cost-effective large-scale production of CdTe photovoltaic modules with uniform thin film deposition, reducing material waste and enabling continuous processing of large substrates, thereby enhancing energy conversion efficiency and reducing production costs.
Implementation Method 1
a thin film of a sublimated source material is deposited onto a top surface of the substrates
Implementation Method 2
the sublimed material moves through holes in a cover placed over the receptacle and deposits onto the stationary glass surface
Data Source
AI summary
A system for vapor deposition of a thin film layer on a photovoltaic module substrate is provided. The system includes a vacuum chamber having a pre-heat section, a vapor deposition apparatus, and a cool-down section; and a conveyor system operably disposed within said vacuum chamber and configured for conveying the substrates in a serial arrangement from said pre-heat section and through said vapor deposition apparatus at a controlled constant linear speed. The vapor deposition apparatus is configured for depositing a thin film of a sublimed source material onto an upper surface of the substrates as the substrates are continuously conveyed by said conveyor system through said vapor deposition apparatus.