Amorphous Copolyester Film for PV Back-Plane Adhesion
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Solution Overview
Problem
Polyester films used as back-planes in photovoltaic cells face challenges with poor dimensional stability, UV stability, and adhesion issues, requiring additional primer and adhesive layers that increase manufacturing complexity and cost.
Innovation Solution
A polyester film with a crystallisable base layer and a heat-sealable amorphous copolyester layer derived from aliphatic and cycloaliphatic diols and aromatic dicarboxylic acids is used, which exhibits excellent adhesion to encapsulant resins, hydrolytic stability, and UV stability, eliminating the need for additional adhesive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional primer and adhesive layers are added to improve adhesion, then adhesion performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the base polyester film with a functional copolyester layer into a single integrated structure. The copolyester layer is formed by reacting terminal hydroxyl groups of the base polyester with dicarboxylic acid and diol, creating a unified multi-functional film that provides both structural support and adhesion properties, eliminating the need for separate primer and adhesive layers.
Solution Approach 2:
The copolyester layer serves multiple functions simultaneously: it provides adhesion to the encapsulant resin, maintains dimensional stability, and offers UV resistance. This multi-functional layer replaces what would traditionally require multiple separate layers (primer for adhesion, adhesive for bonding, and potentially UV protective layer), simplifying the overall device structure.
2Reliability
If multi-layer films with complementary properties are used to improve performance, then functional properties are intensified, but manufacturing complexity increases
Solution Approach 1:
The patent segments the film into two distinct functional zones: a base polyester layer providing mechanical strength and dimensional stability, and a copolyester layer providing adhesion and UV resistance. This segmentation allows each layer to be optimized for its specific function while maintaining a relatively simple two-layer structure compared to traditional multi-layer assemblies.
Solution Approach 2:
The invention creates a composite film structure where a base polyester is chemically modified by adding a copolyester layer formed from dicarboxylic acid and diol reactions. This composite material combines the dimensional stability of crystalline polyester with the adhesion and UV resistance properties of the amorphous copolyester layer, achieving multiple performance goals in a single integrated film.
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 solution provides improved adhesion, hydrolytic stability, and UV stability, reducing manufacturing complexity and costs while maintaining the mechanical and optical properties necessary for photovoltaic cell performance.
Implementation Method 1
said polyester film exhibits excellent adhesion, in particular to encapsulant resins
Implementation Method 2
the polyester film comprises a base layer (B) comprising a crystallisable polyester, and a heat-sealable layer (A) comprising an amorphous copolyester
Implementation Method 3
said polyester film exhibits excellent adhesion, in particular to encapsulant resins, and excellent hydrolytic and UV stability
Data Source
AI summary
A photovoltaic cell comprising a transparent front-plane, an opaque back-plane and an encapsulant resin wherein said back-plane comprises a polyester film comprising a base layer (B) comprising a crystallizable polyester and a heat-sealable layer (A) comprising an amorphous copolyester wherein: (i) said amorphous copolyester is derived from an aliphatic diol and a cycloaliphatic diol and at least one aromatic dicarboxylic acid (ii) said polyester film is disposed in the photovoltaic cell such that layer (A) is in contact with the encapsulant resin.