Aluminum Paste Composition for Solar Cells

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Solution Overview

Problem

Existing aluminum-based pastes for solar cells contain toxic heavy metals, leading to environmental and health concerns, and they struggle to maintain consistent open circuit voltage and structural integrity across varying paste weights, causing bowing and defects in solar cells.

Innovation Solution

A novel aluminum-based paste composition comprising aluminum powder, glass frits, and an organo-aluminate compound, optimized for reduced toxicity, improved viscosity, and enhanced thermal stability, which is applied to the back surface of solar cells to maintain consistent open circuit voltage and reduce bowing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If heavy metals are added to aluminum-based paste to increase solar cell efficiency and open circuit voltage, then the electrical performance is improved, but the toxicity and environmental harm increase

Engineering Contradiction:

Improveopen circuit voltageVSAvoidtoxicity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes heavy metal elements from the aluminum-based paste composition entirely, extracting the harmful substances while maintaining the functional performance through alternative compositional approaches that rely on aluminum powder, glass frit, and organic vehicle without toxic additives

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent modifies the chemical composition parameters of the paste by adjusting the ratios and types of aluminum powder, glass frit, and organic vehicle to achieve the desired open circuit voltage and electrical performance without relying on heavy metal contaminants

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the amount of aluminum paste is varied to cover different solar cell sizes, then the adaptability is improved, but the open circuit voltage becomes inconsistent

Engineering Contradiction:

Improvepaste weight variationVSAvoidopen circuit voltage consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent optimizes the paste composition parameters, particularly the glass frit to aluminum powder ratio and organic vehicle selection, to create a formulation that maintains consistent electrical performance and open circuit voltage across a wide range of paste weights and application conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite material system combining aluminum powder, glass frit, and organic vehicle in specific proportions that creates synergistic effects, allowing the paste to maintain stable electrical properties regardless of variations in total paste amount applied

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional aluminum paste is used, then the manufacturing process is simple, but bowing and structural defects occur in solar cells

Engineering Contradiction:

Improvepaste application simplicityVSAvoidstructural integrity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent adjusts the compositional parameters of the paste, specifically the glass frit content and particle size distribution, to control the firing behavior and thermal expansion characteristics, thereby preventing bowing and structural defects while maintaining ease of application

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite paste formulation where glass frit and aluminum powder work together to provide both structural support and electrical functionality, with the glass frit acting as a flux that promotes proper sintering and reduces thermal stress during the firing process

Inventive Principle:

Principle #40Composite materials

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 novel paste composition achieves consistent open circuit voltage, reduced bowing, and improved structural integrity while being free of toxic heavy metals, enhancing the efficiency and durability of solar cells.

Implementation Method 1

optimized for reduced toxicity, improved viscosity, and enhanced thermal stability

Methodology Applied

Scientific EffectViscosity modification:

Implementation Method 2

During firing, the cell is heated to temperatures above the melting point of aluminum. An aluminum-silicon alloy layer (Al—Si) is thus formed

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 3

Firing also causes a p+ layer (i.e., impurity layer) to form by diffusion of aluminum atoms into the p-type wafer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 4

enhanced thermal stability

Methodology Applied

Scientific EffectThermal stability:

Data Source

PatentUS10026854B2Aluminum-based compositions and solar cells including aluminum-based compositions

Publication Date: 2018.07.17 SUN CHEMICAL CORP

AI summary

The present invention describes an aluminum-based paste composition including an aluminum powder, one or more glass fits, an organo-aluminate compound; and an organic vehicle. The present invention also describes a solar cell including an aluminum-based paste composition applied on a back surface of a silicon wafer.