CIGS Absorber Layer Metal-Alkaline Treatment for Adhesion
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Solution Overview
Problem
In chalcopyrite-based thin-film solar cells, poor adhesion between the absorber and buffer layers due to trapped impurities and sodium-based compound formation along scribe lines, along with a thin oxide layer post-selenization/sulfurization, degrade the p-n junction quality and efficiency.
Innovation Solution
Treating the CIGS absorber layer with a metal-based alkaline solution before buffer layer deposition to improve adhesion and remove impurities, forming a homo-junction and reducing sodium-based compound formation, thereby enhancing the p-n junction quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical bath deposition (CBD) is used to prepare the buffer layer without additional treatment, then the buffer layer can be deposited directly on the absorber layer, but impurities such as oxide or particles are coated by the buffer layer resulting in poor adhesion and delamination
Solution Approach 1:
The patent applies a metal-based alkaline solution treatment to the CIGS absorber layer surface before buffer layer deposition. This preliminary action removes oxide impurities and creates a clean surface, preventing impurity incorporation during subsequent CBD process and ensuring good adhesion between absorber and buffer layers
Solution Approach 2:
The patent extracts harmful oxide impurities from the CIGS absorber layer surface by treating it with metal-based alkaline solution. This extraction process removes the detrimental oxide layer that would otherwise be coated by the buffer layer and cause adhesion problems
2Ease of manufacture
If CBD process is used for buffer layer deposition, then the buffer layer can be formed, but sodium-based compounds leaching from glass substrate diffuse through absorber layer and concentrate along scribe lines forming large particulate impurities
Solution Approach 1:
The metal-based alkaline solution treatment extracts sodium-based compounds from the CIGS absorber layer surface, particularly from scribe line regions where they concentrate during CBD process. This prevents formation of large particulate impurities that would harm cell performance and appearance
Solution Approach 2:
The patent converts the harmful effect of sodium-based compound leaching into a beneficial cleaning process. The metal-based alkaline solution utilizes the leaching phenomenon to its advantage by dissolving and removing sodium compounds from the absorber surface before buffer deposition, transforming a manufacturing defect into a surface preparation opportunity
3Productivity
If selenization or sulfurization is performed to form the absorber layer, then the CIGS layer can be created, but a thin oxide layer forms on the absorber surface degrading p-n junction quality and cell efficiency
Solution Approach 1:
The patent extracts the detrimental oxide layer formed on the CIGS absorber surface after selenization/sulfurization by treating with metal-based alkaline solution. This removal of surface oxide is critical for maintaining high p-n junction quality and cell efficiency
Solution Approach 2:
The oxide removal treatment is performed as a preliminary step immediately after absorber layer formation and before buffer layer deposition. This timing ensures the absorber surface is in optimal condition for achieving high-quality p-n junction interface
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
Significantly reduces delamination and improves the p-n junction quality, leading to enhanced solar cell performance and appearance by ensuring better adhesion and eliminating detrimental impurities.
Implementation Method 1
treating the CIGS absorber layer with a metal-based alkaline solution before buffer layer deposition to improve adhesion and remove impurities
Implementation Method 2
sodium-based compounds leaching out of the glass substrate along the scribe lines diffuse through the absorber layer
Implementation Method 3
forming a homo-junction and reducing sodium-based compound formation, thereby enhancing the p-n junction quality
Data Source
AI summary
A method for manufacturing a thin film solar cell device includes forming a back contact layer on a substrate, forming an CIGS absorber layer on the back contact layer, treating the CIGS absorber layer with a metal-based alkaline solution, and forming a buffer layer on the CIGS absorber layer where the treatment of the CIGS absorber layer improves the adhesion between the CIGS absorber layer and the buffer layer and also improves the quality of the p-n junction at the CIGS absorber layer/buffer layer interface.