CIGS Solar Cell Composition Control via XRF Feedback
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Solution Overview
Problem
Current methods for fabricating copper indium gallium diselenide (CIGS) solar cells lack precise control over the thickness and composition of the deposited CIGS layer, leading to inefficiencies and non-uniformity in solar cell production.
Innovation Solution
Implementing a control method using multiple rows of evaporation sources and sensors to detect the transition point from a Cu-excessive to Cu-deficient composition, allowing for real-time adjustments to maintain a uniform composition and thickness of the CIGS layer through feedback loops and XRF devices for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional co-evaporation deposition methods are used to fabricate CIGS solar cells, then the production process can be implemented, but the thickness and composition of the deposited CIGS layer cannot be precisely controlled, leading to non-uniformity
Solution Approach 1:
The patent implements a feedback control system where sensors continuously monitor the deposition process parameters (such as layer thickness and composition) and provide real-time data to a controller. The controller adjusts the effusion rates of the vapor sources based on this feedback, enabling precise control of the CIGS layer properties while maintaining process stability
Solution Approach 2:
The patent replaces manual or simple mechanical control of deposition parameters with an automated electronic control system. The controller uses electronic signals to precisely regulate the effusion rates of multiple vapor sources, substituting complex mechanical adjustment mechanisms with electronic feedback loops that achieve superior control precision
2Stability of the object's composition
If multiple vapor sources are used to deposit different elements (Cu, Ga, In, Se) simultaneously, then CIGS layer formation is achieved, but the composition varies along the deposition zone making uniform composition difficult to obtain
Solution Approach 1:
The patent applies local quality control by independently controlling the effusion rate of each vapor source (Cu, Ga, In, Se) based on the specific compositional requirements at different locations along the substrate. The controller adjusts each source's contribution to achieve the target CIGS stoichiometry (Cu:In:Ga:Se = 23.5:19.5:7:50 atomic percent) uniformly across the entire deposition zone
Solution Approach 2:
The patent dynamically changes the effusion rates of the vapor sources during the deposition process. The controller monitors the deposited layer composition in real-time and adjusts the temperature and effusion rate parameters of each vapor source to compensate for variations, maintaining uniform CIGS composition throughout the deposition zone while sustaining high productivity
3Measurement precision
If the effusion rates of Cu, Ga, and In are controlled to create composition gradients along the deposition zone, then the CIGS film composition can be varied, but the transition from Cu-rich to Cu-deficient composition cannot be detected or controlled
Solution Approach 1:
The patent employs sensors that continuously monitor the composition of the deposited CIGS layer in real-time. When the composition transitions from Cu-rich to Cu-deficient, the sensor detects this change and provides feedback to the controller, which then adjusts the effusion rates to maintain the desired composition profile
Solution Approach 2:
The patent replaces difficult manual detection methods with automated electronic sensing and control. The system uses electronic sensors to precisely detect composition transitions and electronic controllers to automatically adjust effusion rates, substituting complex manual monitoring and adjustment procedures with automated feedback control
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
This approach ensures high output rates of substrates with accurately controlled composition and thickness, enhancing the efficiency and durability of CIGS solar cells by maintaining a stable transition point and adjusting evaporant fluxes accordingly.
Implementation Method 1
high vacuum co-deposition methods using three or five boats as effusion sources for the elements to be deposited
Implementation Method 2
XRF devices for precise control
Data Source
AI summary
An in-line production apparatus and a method for composition control of copper indium gallium diselenide (CIGS) solar cells fabricated by a co-evaporation deposition process. The deposition conditions are so that a deposited Cu-excessive overall composition is transformed into to a Cu-deficient overall composition, the final CIGS film. Substrates with a molybdenum layer move through the process chamber with constant speed. The transition from copper rich to copper deficient composition on a substrate is detected by using sensors which detect a physical parameter related to the transition. A preferred embodiment sensors are provided that detect the composition of elements in the deposited layer. A controller connected to the sensors adjusts the fluxes from the evaporant sources in order provide a CIGS layer with uniform composition and thickness over the width of the substrate.