Silicon Solar Cell Texturing via Metal Ion Extraction
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Solution Overview
Problem
Current methods for producing textured structures on crystalline silicon solar cells face challenges such as instability and non-uniformity due to Ag ion accumulation in etching solutions, leading to reduced photoelectric conversion efficiency and short solution lifetimes, particularly with the metal ion etching method.
Innovation Solution
A method involving forming a porous layer on silicon wafers, followed by cleaning with an alkaline solution to remove residual metal particles, and then etching with a hydrofluoric acid and nitric acid solution to achieve a stable and uniform textured structure, which includes using water washing steps and specific concentrations of chemical solutions to prevent metal catalysis and extend solution life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If metal ion etching method is used to form textured structure, then surface reflectivity is reduced, but Ag ions accumulate in etching solution causing instability and non-uniformity
Solution Approach 1:
The patent extracts and removes Ag ions from the etching solution through filtration or replacement, preventing their accumulation. This is done by introducing a new etching solution without Ag ions after the initial texturing step, thereby eliminating the source of instability and non-uniformity in subsequent processing.
Solution Approach 2:
The etching process is divided into two distinct stages: first, metal ion-assisted etching to create the initial porous layer and textured structure; second, Ag-ion-free etching to complete the texturing without contamination. This segmentation prevents Ag ion accumulation from affecting the overall process stability.
2Productivity
If metal ion etching is performed repeatedly, then textured structure is formed, but solution lifetime is shortened due to Ag ion accumulation
Solution Approach 1:
The patent discards the Ag-containing etching solution after it has served its purpose in creating the initial textured structure, and replaces it with a fresh Ag-ion-free etching solution. This allows continuous production without the solution lifetime being limited by Ag ion accumulation, effectively recovering the etching capability for extended production runs.
3Ease of manufacture
If Ag ions are present in etching solution, then porous layer formation is enhanced, but metal particles adhere to wafer in reverse direction
Solution Approach 1:
The patent performs the metal ion-assisted etching as a preliminary step to create the porous layer structure, then removes Ag ions before subsequent etching steps. This preliminary action achieves the beneficial porous structure formation while preventing the harmful reverse-direction metal particle adhesion in later stages.
Solution Approach 2:
The patent converts the harmful effect of Ag ion accumulation into a beneficial one by using Ag ions only in the initial etching step where they facilitate porous layer formation, then removing them before they can cause harmful reverse-direction adhesion. The harmful Ag ions are thus utilized beneficially in a controlled manner.
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 significantly prolongs the life of the etching solution, ensures stability and uniformity of the textured structure, and enhances the electrical properties of solar cells by improving open circuit voltage, short circuit current, and photoelectric conversion efficiency.
Implementation Method 1
etching the surface with a first chemical etching solution to obtain a textured structure; wherein the first chemical etching solution is a mixed solution of hydrofluoric acid and nitric acid
Implementation Method 2
cleaning with a first alkaline chemical solution; removing the residual metal particles with a first cleaning solution
Implementation Method 3
placing a silicon wafer in a hydrofluoric acid solution containing an oxidizing agent and a metal salt to form a porous layer structure
Data Source
Figure 1~3
AI summary
The present invention discloses a method for producing a textured structure of a crystalline silicon solar cell, comprising the following steps: (1) forming a porous layer structure on the surface of a silicon wafer; (2) then cleaning with a first alkaline chemical solution; (3) removing residual metal particles with a cleaning solution; (4) and then etching the surface with a first chemical etching solution to obtain the textured structure of the crystalline silicon solar cell. The present invention greatly prolongs the lifetime of the mixed solution of hydrofluoric acid and nitric acid and ensures the stability and uniformity of the textured structure.