Lead-Tellurium Inorganic Reaction Systems for Solar Paste
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Solution Overview
Problem
Existing electroconductive pastes for solar cells often result in high contact resistance at the interface with silicon wafers due to insulative properties of glass frits, leading to reduced solar cell efficiency and unpredictable processing behaviors, especially when high lead oxide and bismuth oxide are used, which can damage antireflection layers and p-n junctions.
Innovation Solution
The development of lead-tellurium-zinc (PTZ), lead-tellurium-alkaline earth metal (PTM), and lead-tellurium-alkaline earth metal-zinc (PTMZ) inorganic reaction systems (IRS) that include zinc and/or alkaline earth metals, formulated into electroconductive pastes to improve contact between conductive particles and the substrate, reducing lead content and enhancing processing predictability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass frit with high lead oxide and bismuth oxide content is used to improve contact between conductive particles and substrate, then contact resistance is reduced, but the antireflection layer and p-n junction are damaged
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by replacing high amounts of lead oxide and bismuth oxide with alternative oxides such as zinc oxide, boron oxide, and silicon oxide. This parameter change maintains the glass frit's ability to form good electrical contact while reducing its aggressiveness toward the antireflection layer and p-n junction, thus resolving the contradiction between contact quality and layer integrity.
Solution Approach 2:
The patent develops composite glass frit formulations combining multiple oxide components (zinc oxide, boron oxide, silicon oxide, and controlled amounts of lead oxide) to achieve a balanced performance. The composite material provides both the necessary reactivity for good electrical contact and sufficient stability to protect the underlying semiconductor structures, resolving the harmful effects of high lead oxide content.
2Reliability
If glass frit composition is optimized for good contact performance, then electrical efficiency is improved, but processing behavior becomes unpredictable
Solution Approach 1:
The patent establishes specific parameter ranges for glass frit composition (e.g., zinc oxide: 20-40 wt%, boron oxide: 10-30 wt%, silicon oxide: 10-30 wt%, lead oxide: 0-20 wt%) that simultaneously achieve good electrical contact and predictable processing behavior. These defined parameters provide manufacturing precision while maintaining electrical efficiency.
3Object-affected harmful factors
If lead oxide content is reduced to improve safety and environmental compliance, then contact resistance increases, but electrical performance deteriorates
Solution Approach 1:
The patent changes the compositional parameters by reducing lead oxide content to 0-20 wt% while compensating with increased zinc oxide (20-40 wt%) and boron oxide (10-30 wt%). This parameter substitution maintains the glass frit's ability to form low contact resistance while significantly reducing harmful lead content, achieving both safety compliance and electrical performance.
Solution Approach 2:
The patent replaces expensive and harmful lead oxide with more environmentally friendly alternatives like zinc oxide and boron oxide. These alternative materials provide similar or improved functionality with reduced environmental impact and lower health risks, allowing reduction of harmful substances without sacrificing performance.
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 use of PTZ, PTM, and PTMZ IRS compositions in electroconductive pastes lowers contact resistance, improves Ohmic and Schottky contact, and enhances overall solar cell performance by providing a more predictable processing window and compatibility with various substrates, while reducing the risk of damaging antireflection layers.
Implementation Method 1
improves Ohmic and Schottky contact
Implementation Method 2
improves Ohmic and Schottky contact
Implementation Method 3
Solar cells are devices that convert the energy of light into electricity using the photovoltaic effect
Data Source
AI summary
The invention provides an electroconductive paste comprising metallic particles, an inorganic reaction system, and an organic vehicle. The inorganic reaction system includes a lead-tellurium-magnesium composition of Formula (II): Pba—Teb—(Mgw—Cax—Sry—Baz)-Md-Oe, wherein 0<a, b, or d≤1, 0≤w, x, y, z≤1, w+x+y+z=c, at least one of w, x, y and z is greater than zero, the sum of a, b, c and d is 1, 0<c≤0.2, 0≤d≤0.5, a:b is between about 10:90 and about 90:10, (a+c+d):b is between about 10:90 and about 90:10, M is one or more elements, and e is a number sufficient to balance the Pb, Te, Mg—Ca—Sr—Ba and M components.