Alkali Control Layer for CIS Solar Cell Efficiency
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Solution Overview
Problem
Conventional methods using high strain point glass substrates in CIS-based thin film solar cells fail to achieve high photoelectric conversion efficiency due to insufficient alkali metal diffusion, leading to suboptimal crystal growth and carrier concentration in the p-type light absorption layer.
Innovation Solution
A method involving the formation of an alkali control layer on high strain point glass substrates to allow controlled diffusion of alkali metals, supplemented by external addition of alkali metals to the CIS-based light absorption layer, enabling high-temperature film formation without substrate deformation and improving layer quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an alkali diffusion prevention layer is provided to completely prevent diffusion of Na from the glass substrate, then substrate deformation is prevented, but the photoelectric conversion efficiency decreases due to insufficient alkali metal in the light absorption layer
Solution Approach 1:
An alkali control layer with intermediate permeability is introduced between the glass substrate and the light absorption layer. This layer acts as a mediator that allows controlled diffusion of alkali metals from the substrate while blocking excessive diffusion, thereby resolving the contradiction between maintaining substrate integrity and achieving sufficient alkali metal concentration for high photoelectric conversion efficiency
Solution Approach 2:
The diffusion characteristics of the alkali control layer are optimized by controlling its thickness (5-50 nm) and material composition. By adjusting these parameters, the layer enables sufficient alkali metal diffusion for efficient photoelectric conversion while preventing substrate deformation, thus resolving the contradiction between the two opposing requirements
2Manufacturing precision
If Na is added from the outside to achieve sufficient alkali metal concentration, then photoelectric conversion efficiency is improved, but the device complexity increases due to additional process steps
Solution Approach 1:
The alkali control layer enables the glass substrate to self-supply alkali metals to the light absorption layer through controlled diffusion during the film formation process. This self-service mechanism eliminates the need for external alkali metal addition processes, thereby maintaining high photoelectric conversion efficiency while reducing process complexity
Solution Approach 2:
The alkali control layer combines multiple functions: it controls alkali metal diffusion, serves as part of the film formation process, and eliminates the need for separate alkali metal addition steps. By merging these functions into a single layer, the solution achieves high photoelectric conversion efficiency without increasing device complexity
3Manufacturing precision
If the film forming temperature is raised to improve layer quality, then photoelectric conversion efficiency is improved, but the glass substrate deforms due to its low strain point
Solution Approach 1:
The alkali control layer is formed beforehand with optimized thickness and composition to enable controlled alkali metal diffusion. This preliminary preparation allows the subsequent high-temperature film formation process to proceed without substrate deformation, as the layer acts as a buffer that manages the thermal and chemical interactions between the substrate and the light absorption layer
4Quantity of substance
If a thin alkali control layer is used to allow alkali metal diffusion, then sufficient alkali metal reaches the light absorption layer, but excessive diffusion may occur causing peeling
Solution Approach 1:
The thickness of the alkali control layer (5-50 nm) and its material composition are precisely controlled to optimize alkali metal diffusion. By adjusting these parameters, the layer allows sufficient alkali metal diffusion for high photoelectric conversion efficiency while maintaining adhesion strength and preventing peeling, thus resolving the contradiction between quantity of substance and strength
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 sufficient alkali metal concentration in the CIS-based light absorption layer, allowing for high photoelectric conversion efficiency while preventing unnecessary element diffusion and maintaining substrate integrity, thereby enhancing the solar cell's performance.
Implementation Method 1
the alkali control layer is formed to a thickness which allows diffusion by heat treatment of the alkali metal which is contained in the high strain point glass substrate to the CIS-based light absorption layer
Data Source
AI summary
A method of production of a CIS-based thin film solar cell comprises the steps of forming an alkali control layer on a high strain point glass substrate, forming a back surface electrode layer on the alkali control layer, forming a CIS-based light absorption layer on the back surface electrode layer, and forming an n-type transparent conductive film on the CIS-based light absorption layer, wherein the alkali control layer is formed to a thickness which allows heat diffusion of the alkali metal which is contained in the high strain point glass substrate to the CIS-based light absorption layer and, furthermore, the CIS-based light absorption layer has an alkali metal added to it from the outside in addition to heat diffusion from the high strain point glass substrate.