Solar Cell Back Passivation Stack for PID and Cost Reduction
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Solution Overview
Problem
Existing PERC solar cells with aluminum oxide/silicon nitride stacks face challenges in enhancing back passivation characteristics, reducing potential induced degradation (PID), and lowering manufacturing costs for industrial mass production.
Innovation Solution
A solar cell design featuring a passivation film stack on the back surface, comprising a silicon-rich layer, an oxygen-rich and nitrogen-rich layer, and a silicon nitride film with a gradient-varied refractive index, replaces the conventional aluminum oxide/silicon nitride stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum oxide/silicon nitride stack is used as back passivation layer, then passivation effect is improved, but equipment cost increases and production capacity decreases
Solution Approach 1:
The patent replaces expensive aluminum oxide/silicon nitride stack with a cheaper silicon-rich silicon oxynitride-based passivation layer that can be deposited using standard PECVD equipment, reducing both material and equipment costs while maintaining passivation effectiveness
Solution Approach 2:
The patent modifies the composition parameters of the passivation layer by creating a silicon-rich silicon oxynitride-based layer with specific silicon atom concentration (5×10^21/cm³ to 2.5×10^22/cm³), which changes the electrical and optical properties to achieve good passivation without requiring expensive aluminum oxide materials
2Reliability
If aluminum oxide/silicon nitride stack is used as back passivation layer, then passivation effect is improved, but manufacturing cost increases
Solution Approach 1:
The patent substitutes expensive aluminum oxide/silicon nitride materials with inexpensive silicon-rich silicon oxynitride-based materials that can be processed using conventional PECVD equipment already available in solar cell manufacturing lines, significantly reducing manufacturing costs
Solution Approach 2:
The patent extracts and removes the aluminum oxide component from the passivation stack, retaining only the essential silicon-based passivation functionality that can be achieved more cost-effectively using silicon-rich silicon oxynitride deposited by standard equipment
3Ease of manufacture
If conventional passivation film is used, then manufacturing cost is reduced, but back passivation characteristics are insufficient
Solution Approach 1:
The patent creates a composite silicon-rich silicon oxynitride-based passivation layer that combines the benefits of silicon oxide (good passivation) and silicon nitride (chemical stability), achieving superior back passivation characteristics while maintaining cost-effectiveness through standard PECVD processing
Solution Approach 2:
The patent optimizes the local composition of the passivation layer by controlling silicon atom concentration to be silicon-rich (5×10^21/cm³ to 2.5×10^22/cm³), creating localized regions with enhanced passivation properties without requiring expensive materials throughout the entire structure
4Ease of manufacture
If EVA encapsulating material is used, then manufacturing cost is reduced, but PID phenomenon occurs on back surface
Solution Approach 1:
The patent converts the potential harm of using low-cost EVA encapsulant by pairing it with a specifically designed silicon-rich passivation layer that creates a protective barrier, preventing Na+ ion migration from the EVA to the solar cell and eliminating PID issues while maintaining cost advantages
Solution Approach 2:
The silicon-rich silicon oxynitride-based passivation layer acts as an intermediary barrier between the EVA encapsulant and the solar cell, blocking the migration path of Na+ ions and preventing the harmful interaction that causes PID, while allowing the use of cost-effective EVA material
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
This design effectively enhances back passivation characteristics, reduces PID in photovoltaic modules, and lowers manufacturing costs compared to conventional solar cells.
Implementation Method 1
An aluminum oxide film contains a high fixed negative charge density, and a large number of fixed negative charges may shield electrons on a silicon surface, thereby reducing electrons that can be used for recombination and thus achieving a purpose of suppressing carrier recombination on the surface. Due to the high fixed negative charge density, a strong field passivation effect may be generated
Implementation Method 2
A main reason for the potential induced degradation lies in that Na+ ions inside glass of an encapsulating material of the photovoltaic (PV) module migrate to inside of the solar cell along a direction of the solar cell to destroy a p-n junction
Data Source
AI summary
Provided is a solar cell. The solar cell may include a semiconductor layer and a passivation film stack provided on a back surface of the semiconductor layer. The passivation film stack may include a first passivation layer provided on the back surface of the semiconductor layer and including a silicon-rich layer with a silicon atom concentration ranging from 5×1021/cm3 to 2.5×1022/cm3; a second passivation layer provided on a surface of the first passivation layer and including an oxygen-rich and nitrogen-rich layer; and a third passivation layer provided on a surface of the second passivation layer and including at least one silicon nitride film with a gradient-varied refractive index. A first refractive index of the first passivation layer may be greater than a second refractive index of the second passivation layer and smaller than a third refractive index of the third passivation layer.