Polyimide Resin Back Reflection Layer for Solar Cells
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Solution Overview
Problem
Crystalline silicon solar cells face issues with substrate warping due to thermal expansion differences, high carrier recombination, and low reflectance, especially when thinning, which hinder efficiency and cost-effectiveness, and existing solutions like backside passivation layers are costly and complex to produce.
Innovation Solution
A polyimide resin composition with dispersed light-reflecting particles is used to form a back reflection layer in solar cells, providing excellent heat resistance and durability, and can be applied simply and cost-effectively using a solvent-soluble polyimide resin with a mixed solvent system, suitable for screen printing or dispense methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silicon oxide film or silicon nitride film is formed on the back surface to create a back reflection layer, then reflectance is improved, but production cost increases due to required photolithography and etching processes
Solution Approach 1:
The patent changes the material parameter from traditional silicon oxide or silicon nitride films to a polyimide-based resin composition. This material substitution eliminates the need for complex photolithography and etching processes, reducing production cost while maintaining or improving reflectance properties through the polyimide matrix combined with light-reflecting particles.
Solution Approach 2:
The patent creates a composite back reflection layer by combining polyimide resin with light-reflecting particles. This composite structure achieves high reflectance through the dispersed light-reflecting particles while the polyimide matrix provides structural integrity and adhesion, eliminating the need for expensive semiconductor processing steps required by traditional single-material approaches.
2Illumination intensity
If the back surface is fully covered with aluminum or silver paste to increase reflectance, then reflectance is improved, but substrate warping occurs due to thermal expansion differences during calcination
Solution Approach 1:
The patent changes the material composition parameter by replacing full aluminum or silver paste coverage with a polyimide-based resin composition containing light-reflecting particles. This material substitution reduces thermal expansion mismatch while maintaining reflectance, thereby preventing substrate warping during the calcination process.
Solution Approach 2:
The patent applies local quality by creating a back reflection layer with specific localized properties - the polyimide resin composition provides both reflectance (through light-reflecting particles) and thermal compatibility (through its expansion characteristics), addressing both reflectance and warping issues simultaneously in the back reflection layer region without requiring full metal paste coverage.
3Manufacturing precision
If traditional semiconductor processing techniques are used to form back reflection layers, then manufacturing precision is improved, but device complexity increases due to multiple processing steps
Solution Approach 1:
The patent merges multiple functions into a single material - the polyimide resin composition simultaneously provides adhesion, reflectance (through dispersed particles), and structural stability. This consolidation eliminates the need for separate photolithography, etching, and film deposition steps, reducing device complexity while maintaining manufacturing precision through direct coating and curing processes.
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
The polyimide resin composition enhances the solar cell's conversion efficiency and reliability by improving reflectance and durability, allowing for a cost-effective and straightforward method to form a back reflection layer, thereby addressing the limitations of existing technologies.
Implementation Method 1
light-reflecting particles dispersed in the organic solvent
Implementation Method 2
heat-resistant resins represented by polyimide resins have been widely used as surface protective films or interlayer insulation films of semiconductor devices in the field of electronics since they have superior heat resistance
Data Source
AI summary
Disclosed are a method of forming a back reflection layer in a solar cell, a composition used therefor, and a solar cell having a back reflection layer formed by the method, which layer has superior heat-resistance and various types of durabilities, and can contribute to improving the conversion rate of solar cells and reliability during long-term use, and which method can form a back reflection layer in a solar cell easily and at low cost. The polyimide resin composition for use in forming a back reflection layer in a solar cell includes an organic solvent, a polyimide resin dissolved in the organic solvent, and light-reflecting particles dispersed in the organic solvent.