Sodium Doped CIGS Absorber via Segmented Doping
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Solution Overview
Problem
Existing thin-film photovoltaic technologies face limitations in achieving high efficiency due to poor sodium doping methods, which affect the integration of electrode materials and grain formation in copper-based absorber materials, particularly for large-scale manufacturing.
Innovation Solution
A method involving sodium doping pathways, including in-chamber sputtering and gas-phase diffusion, is employed to form a CIGS/CIGSS-based absorber material, using a soda lime glass substrate with a barrier material to prevent sodium diffusion, and a thermal treatment process with H2Se and nitrogen to achieve optimal sodium concentration and composition ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sodium doping methods are used in thin-film photovoltaic manufacturing, then the doping process is simple, but the photovoltaic efficiency is poor and grain formation is affected
Solution Approach 1:
The doping process is segmented into multiple distinct pathways: (1) in-chamber sputtering with sodium-containing targets, (2) post-deposition sodium exposure, and (3) thermal treatment with H2Se and nitrogen. Each pathway can be independently controlled and optimized, allowing precise sodium concentration control while maintaining manufacturing feasibility.
Solution Approach 2:
The patent controls sodium doping by changing multiple parameters including: sodium concentration in target materials, sputtering power and time, thermal treatment temperature and duration, and gas composition ratios. These parameter changes enable precise control of sodium concentration in the absorber layer to achieve optimal photovoltaic efficiency.
2Stability of the object's composition
If sodium is doped to enhance grain formation, then grain size is improved, but electrode material integration is harmed
Solution Approach 1:
The patent applies different sodium concentrations and doping pathways to different regions and layers. Sodium is primarily doped into the absorber layer through controlled sputtering and thermal treatment, while electrode interfaces are protected by optimizing deposition sequences and using barrier layers where necessary. This local quality control ensures grain formation in the absorber without compromising electrode integration.
Solution Approach 2:
Sodium doping is performed as a preliminary action during the absorber layer deposition process itself, through in-chamber sputtering with sodium-containing targets. This preliminary sodium incorporation establishes optimal grain formation conditions before electrode deposition, preventing subsequent electrode integration issues while ensuring proper grain structure.
3Manufacturing precision
If multiple sodium doping pathways are used, then sodium concentration control is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges multiple sodium doping functions into integrated process steps. For example, sodium-containing target materials are used during standard sputtering deposition, combining layer formation and sodium doping into a single step. Thermal treatment simultaneously achieves sodium diffusion, grain growth, and phase formation, reducing the number of separate process steps while maintaining precise sodium concentration 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 results in high-efficiency thin-film photovoltaic devices with solar energy conversion efficiency of 15% or higher, by controlling sodium doping and copper-to-indium-gallium composition, enhancing grain size and stability, and simplifying the doping process.
Implementation Method 1
forming a barrier material overlying the surface region. The barrier material is configured to prevent a diffusion of a second sodium ion from the soda lime glass substrate
Implementation Method 2
sputtering a first target device including a first mixture of a copper species, gallium species, and a first sodium species to form a first thickness of a first precursor material overlying the electrode material
Implementation Method 3
subjecting the soda lime glass substrate having the stack structure in a thermal treatment process with H2Se gas species and nitrogen species at a temperature above 400° C. to cause formation of an absorber material from interdiffusion of the copper species, the gallium species, the indium species, and the first sodium species
Implementation Method 4
transferring a second sodium species from a portion of the soda lime glass substrate via gas-phase diffusion during a portion of time associated with the thermal treatment process
Data Source
AI summary
A method of processing a thin-film absorber material with enhanced photovoltaic efficiency. The method includes providing a soda-lime glass substrate having a surface region and forming a barrier material overlying the surface region, followed by formation of a stack structure including a first thickness of a first precursor, a second thickness of a second precursor, and a third thickness of a third precursor. The first thickness of the first precursor is sputtered with a first target device including a first mixture of copper, gallium, and a first sodium species. The method further includes subjecting the soda-lime glass substrate having the stack structure in a thermal treatment process with at least H2Se gas species at a temperature above 400° C. to cause formation of an absorber material. Moreover, the method includes transferring a second sodium species from a portion of the soda-lime glass substrate via gas-phase diffusion during the thermal treatment process.