CIGS Solar Cell Sodium Diffusion Control
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Solution Overview
Problem
Existing methods for manufacturing CIGS-based thin-film solar cells face challenges in controlling the diffusion of Na ions, which affects the electrical characteristics of the solar cells, and require additional processes or materials that complicate the manufacturing process.
Innovation Solution
The method involves forming Na halide sources on the surface of a molybdenum electrode using a mask in a vacuum chamber before forming the CIGS-based precursor thin film and subsequent heat treatment with selenium to diffuse Na into the film, utilizing a Na-free substrate to prevent random Na diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Na supply sources are formed on the molybdenum electrode surface before CIGS precursor thin film formation, then Na diffusion into the CIGS-based thin film is controlled and electrical characteristics are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies sodium halide sources to the molybdenum electrode surface before forming the CIGS precursor thin film. This preliminary action ensures that sodium is already positioned on the electrode when the CIGS layer is deposited, enabling controlled diffusion during subsequent heat treatment without requiring additional post-processing steps.
Solution Approach 2:
The patent uses sodium halide (NaCl, NaBr, or NaI) as an intermediary substance to supply sodium to the CIGS-based thin film. The sodium halide is applied to the molybdenum electrode and serves as a controlled sodium source that releases sodium ions during heat treatment, improving electrical characteristics without requiring direct sodium metal handling.
2Reliability
If additional thermal process is used to diffuse Na into the light-absorbing layer, then Na diffusion is achieved, but the overall process time is lengthened
Solution Approach 1:
The patent combines the sodium diffusion process with the existing selenization heat treatment step. By applying sodium halide sources before CIGS precursor deposition and then performing a single heat treatment step that accomplishes both sodium diffusion and selenization, the patent eliminates the need for separate thermal processing steps, thereby reducing overall process time while achieving effective sodium diffusion.
3Quantity of substance
If Na doping is performed on the molybdenum electrode, then Na supply is achieved, but the conductivity of molybdenum is deteriorated
Solution Approach 1:
The patent applies sodium halide sources only to specific regions of the molybdenum electrode surface where CIGS precursor thin film will be formed, rather than doping the entire molybdenum electrode. This localized application ensures that sodium is supplied only where needed for CIGS layer formation, maintaining the conductivity of the bulk molybdenum electrode while achieving sufficient sodium content in the CIGS-based thin film.
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 improves the electrical characteristics and efficiency of the CIGS-based thin-film solar cells by controlled Na diffusion, preventing random Na ion diffusion and simplifying the manufacturing process.
Implementation Method 1
heat-treating the CIGS-based precursor thin film with selenium to diffuse Na from the Na supply sources into the CIGS-based precursor thin film
Data Source
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AI summary
Disclosed herein is a method of manufacturing CIGS-based thin-film solar cell, including the steps of: forming molybdenum electrode on Na-free substrate (S1); forming Na supply sources on parts of the surface of the molybdenum electrode (S2); forming CIGS-based precursor thin film on the molybdenum electrode (S3); and heat-treating the CIGS-based precursor thin film with selenium to diffuse Na from the Na supply sources into the CIGS-based precursor thin film, thus forming CIGS-based thin film (S4). The method is advantageous in that the random diffusion of Na can be prevented due to using Na-free substrate, and that Na is supplied into CIGS-based thin film serving as a light-absorbing layer of a solar cell by additional Na supply sources, thus improving the efficiency of a solar cell.