PERC Photovoltaic Cell Rear Passivation for Anti-PID Performance
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Solution Overview
Problem
Passivated Emitter and Rear Cell (PERC) based photovoltaic modules suffer from potential induced degradation (PID) effects, leading to reduced conversion efficiency and power generation due to potential differences between cells and packaging materials.
Innovation Solution
A photovoltaic cell design that includes a substrate with a first passivation layer and anti-reflection layer on the front surface, and a second passivation layer, a polarization phenomenon weakening (PPW) layer, and multiple silicon nitride layers on the rear surface, optimized in terms of refractive index and thickness to reduce potential differences and enhance anti-PID performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PERC structure with aluminum oxide/silicon nitride rear passivation layer is used, then carrier recombination suppression is achieved, but potential induced degradation (PID) effect occurs leading to reduced power generation efficiency
Solution Approach 1:
The patent divides the rear passivation layer into multiple distinct layers: a first silicon nitride layer (5-20 nm), a second silicon nitride layer (20-40 nm), and a third silicon nitride layer (40-75 nm), each with optimized thickness. This segmentation allows each layer to contribute differently to both PID resistance and optical performance, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent employs a composite structure combining multiple silicon nitride layers with different thicknesses and refractive indices, along with aluminum oxide layers, to create a multi-functional rear passivation system. This composite approach enables simultaneous achievement of electrical passivation (anti-PID) and optical management (anti-reflection), thereby maintaining high power generation efficiency while improving anti-PID performance.
2Reliability
If multiple silicon nitride layers with optimized refractive indices are added to the rear surface, then anti-PID performance is improved, but device complexity increases
Solution Approach 1:
The patent designs the silicon nitride layers to serve multiple functions simultaneously: electrical passivation to prevent PID effects, optical anti-reflection through refractive index optimization, and surface field effect passivation. This multi-functionality reduces the need for separate dedicated layers, thereby limiting the increase in device complexity while achieving improved anti-PID performance.
3Productivity
If the thickness of silicon nitride layers is optimized to 50-100 nm, then anti-reflection performance is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies optimized thickness ranges for each silicon nitride layer (first: 5-20 nm, second: 20-40 nm, third: 40-75 nm) rather than a single fixed thickness. This parameter optimization within ranges allows manufacturing flexibility while achieving the desired anti-reflection performance through constructive interference of reflected light waves, thereby balancing productivity improvement with manageable manufacturing precision requirements.
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 proposed design significantly improves anti-PID performance, leading to enhanced power generation efficiency and extended lifespan of photovoltaic cells by minimizing power loss and light attenuation.
Implementation Method 1
a polarization phenomenon weakening (PPW) layer and at least one silicon nitride layer SiuNv that are sequentially disposed on a rear surface of the substrate... a refractive index of the at least one silicon oxynitride layer is in a range of 1.5 to 1.8, and a thickness of the at least one silicon oxynitride layer is in a range of 1 nm to 30 nm
Implementation Method 2
An aluminum oxide layer has a relatively high fixed negative charge density, and a large number of the fixed negative charges may shield electrons on a silicon substrate surface, thus reducing the electrons usable for recombination and achieving suppression of carrier recombination on the surface
Implementation Method 3
a second passivation layer, a polarization phenomenon weakening (PPW) layer and at least one silicon nitride layer SiuNv that are sequentially disposed on a rear surface of the substrate... a refractive index of the at least one silicon nitride layer is in a range of 1.9 to 2.5
Data Source
AI summary
The photovoltaic cell includes a silicon substrate, a first passivation layer, a second passivation layer, at least one silicon oxynitride layer, and at least one silicon nitride layer. The second passivation layer includes a first silicon oxide layer and at least one aluminum oxide layer, and a thickness of the at least one aluminum oxide layer is in a range of 4 nm to 20 nm. The number of silicon atoms is greater than the number of oxygen atoms in the at least one silicon oxynitride layer and the number of oxygen atoms is greater than the number of nitride atoms in the at least one silicon oxynitride layer. The first silicon oxide layer is disposed between the substrate and the at least one aluminum oxide layer, and a thickness of the first silicon oxide layer is in a range of 0.1 nm to 5 nm.