Polycarbonate Backsheet for Photovoltaic Modules

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Solution Overview

Problem

Photovoltaic module backsheets face issues with environmental unfriendliness, high manufacturing costs, and interlayer delamination due to insufficient adhesive bonding, particularly when using fluoropolymer-based laminates, which lack durability under high humidity and heat exposure.

Innovation Solution

A polycarbonate composition comprising dimethyl bisphenol cyclohexane carbonate and bisphenol-A carbonate units, combined with polyphthalate carbonate copolymers and bisphenol-A polycarbonate homopolymers, is used to create a multilayer sheet with enhanced hydrothermal resistance, impact resistance, and UV weathering protection, allowing for a single-step co-extrusion process that reduces manufacturing costs and improves bonding strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluoropolymer-based laminates (PVF-PET-PVF) are used for backsheets, then weathering resistance and mechanical strength are improved, but manufacturing cost increases and environmental friendliness deteriorates

Engineering Contradiction:

Improveweathering resistanceVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the chemical composition parameters by using DMBPC polycarbonate copolymer instead of traditional PVF-PET-PVF laminate, achieving comparable weathering resistance with lower manufacturing cost and improved environmental compatibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite material system by blending DMBPC polycarbonate copolymer with other polymers to achieve the desired balance of weathering resistance, mechanical strength, and cost-effectiveness in a single-layer backsheet

Inventive Principle:

Principle #40Composite materials

2Strength

If adhesive layers are used to bond PET and PVF layers together, then layer bonding is achieved, but bonding strength is insufficient and interlayer delamination occurs during long-term outdoor exposure

Engineering Contradiction:

Improvebonding strengthVSAvoidresistance to interlayer delamination

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent merges multiple layers into a single-layer polycarbonate backsheet structure, eliminating the need for adhesive bonding between layers and preventing interlayer delamination while maintaining overall structural integrity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts and removes the adhesive layers from the backsheet structure, replacing the multi-layer laminated design with a single-layer polycarbonate construction that inherently provides sufficient bonding without additional adhesive components

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If DMBPC polycarbonate copolymer is used to provide moisture resistance and water vapor barrier, then these properties are improved, but impact resistance becomes inadequate

Engineering Contradiction:

Improvemoisture resistanceVSAvoidimpact resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent employs composite material strategies by blending DMBPC polycarbonate copolymer with other polymers in specific ratios, achieving a balance where both moisture resistance and impact resistance properties are satisfied simultaneously

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by optimizing the composition and thickness of the polycarbonate backsheet to provide enhanced moisture resistance in critical areas while maintaining adequate impact resistance across the entire structure

Inventive Principle:

Principle #3Local quality

4Ease of manufacture

If PET film is used for low cost plastic films with good mechanical and electrical properties, then cost is reduced, but hydrolysis susceptibility increases under high humidity and hot environments

Engineering Contradiction:

Improvemanufacturing costVSAvoidhydrolysis resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the material composition parameter by substituting PET with DMBPC polycarbonate copolymer, which provides comparable cost-effectiveness with superior hydrolysis resistance under high humidity and temperature conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent adopts a cost-effective single-layer polycarbonate backsheet design that eliminates the need for expensive multi-layer laminates while providing durable performance, effectively replacing costly adhesive-bonded structures with a more economical and reliable single-material solution

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS9441106B2Composition, multilayer sheets made therefrom, and methods for making and using the same

Publication Date: 2016.09.13 SABIC GLOBAL TECHNOLOGIES BV

AI summary

In an embodiment, a photovoltaic module, comprises a transparent superstrate; a backsheet, wherein the backsheet comprises a core layer comprising a core composition formed from a first polycarbonate comprising dimethyl bisphenol cyclohexane carbonate repeat units and bishpenol-A, wherein the first polycarbonate has the structurewherein the dimethyl bisphenol cyclohexane carbonate repeat units are present in an amount of 10 wt. % to 50 wt. %, based on the total repeat units in the core composition; and a second polycarbonate selected from the group consisting of a bisphenol-A polycarbonate homopolymer, a polyphthalate carbonate copolymer, a polycarbonate copolymer comprising 2-phenyl-3,3-bis(4-hydroxyphenyl) phthalimidine carbonate and bisphenol-A carbonate repeat units, a polycarbonate copolymer comprising bisphenol-A carbonate and tetrabromobisphenol A carbonate repeat units, and combinations comprising at least one of the foregoing; and a photovoltaic cell between the superstrate and the backsheet.