Sodium-Containing CIGS Sputtering Targets for Solar Cell Efficiency
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Solution Overview
Problem
Existing methods for fabricating copper-indium-gallium-selenide solar cells face challenges in controlling sodium diffusion and achieving efficient p-type conductivity, particularly with non-glass substrates, leading to poor adhesion and reduced solar cell efficiency.
Innovation Solution
The development of sputtering targets incorporating a sodium-containing compound along with copper, indium, and gallium, which are used to form a p-type copper-indium-gallium-selenide layer through reactive sputtering, enhancing the open circuit voltage and fill factor of solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sodium diffusion methods are used from glass substrates, then p-type conductivity is achieved, but control over sodium diffusion is difficult and adhesion is poor with non-glass substrates
Solution Approach 1:
The patent incorporates sodium into the sputtering target material before the deposition process begins. This preliminary incorporation allows for controlled and uniform sodium distribution in the CIGS layer during sputtering, eliminating the need for post-deposition sodium diffusion from substrates and enabling precise control over sodium content regardless of substrate type.
Solution Approach 2:
The patent extracts the sodium supply source from the substrate (glass) and relocates it to the sputtering target. This extraction resolves the adhesion problem with non-glass substrates by eliminating the need for substrate-based sodium diffusion, while maintaining reliable p-type conductivity through controlled sodium incorporation during target deposition.
2Reliability
If sodium is diffused from glass substrates to achieve p-type conductivity, then conductivity is improved, but the process is time-consuming and difficult to control
Solution Approach 1:
By pre-incorporating sodium into the sputtering target, the patent eliminates the time-consuming post-deposition diffusion process. Sodium is introduced uniformly during the main deposition step, significantly reducing processing time while maintaining reliable p-type conductivity control.
3Adaptability or versatility
If traditional fabrication methods are used, then glass substrates work, but adhesion and efficiency are reduced with non-glass substrates
Solution Approach 1:
The patent creates a universal sodium incorporation method through sputtering that works with all substrate types (glass, metal, plastic). By moving sodium supply from substrate-specific diffusion to target-based deposition, the process achieves substrate independence while maintaining reliable adhesion and efficiency across different material platforms.
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 efficiency of solar cells by controlled sodium incorporation, increasing p-type conductivity and reducing the limitations associated with traditional sodium diffusion methods, while also allowing for the use of various substrates beyond glass.
Implementation Method 1
forming a compound semiconductor layer comprising copper, indium, gallium, selenium and sodium by reactive sputtering at least one first target including copper, indium, gallium and a sodium compound
Data Source
AI summary
A sputtering target includes at least one metal selected from copper, indium and gallium and a sodium containing compound.