PERC Photovoltaic Cell Rear Passivation Stack for Anti-PID
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Solution Overview
Problem
Passivated emitter and rear cell (PERC) photovoltaic modules face potential induced degradation (PID) issues due to potential differences between cells and packaging materials, leading to reduced conversion efficiency and power generation.
Innovation Solution
Incorporating a polarization phenomenon weakening (PPW) layer with a silicon oxynitride layer between the aluminum oxide and silicon nitride layers on the rear surface of the photovoltaic cell, optimizing the refractive indices and thicknesses of these layers to reduce potential differences and enhance anti-PID performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PERC structure with aluminum oxide and silicon nitride layers is used, then carrier recombination suppression is achieved, but potential induced degradation (PID) occurs due to potential differences
Solution Approach 1:
A silicon oxynitride layer is introduced as an intermediary layer between the aluminum oxide layer and the silicon nitride layer. This intermediate layer acts as a mediator to reduce the potential difference between the highly negative charged aluminum oxide layer and the silicon nitride layer, thereby suppressing PID effects while maintaining the carrier recombination suppression function of the original structure.
Solution Approach 2:
The patent creates a composite passivation layer structure combining aluminum oxide, silicon oxynitride, and silicon nitride layers. Each material contributes different properties: aluminum oxide provides strong passivation and negative charge, silicon oxynitride provides intermediate properties and reduced potential difference, and silicon nitride provides additional passivation and protection. The composite structure achieves both high anti-PID performance and maintained conversion efficiency.
2Reliability
If the aluminum oxide layer with high fixed negative charge density is used, then carrier recombination is suppressed, but potential difference with packaging materials increases causing PID
Solution Approach 1:
The silicon oxynitride layer serves as a buffer or intermediary between the aluminum oxide layer with high fixed negative charge and the silicon nitride layer. It reduces the abrupt potential difference that would otherwise exist between these two layers, preventing the harmful PID effect while allowing the aluminum oxide layer to maintain its carrier recombination suppression function.
Solution Approach 2:
The patent changes the electrical and optical parameters of the passivation stack by introducing silicon oxynitride with intermediate properties. The silicon oxynitride layer has a refractive index and electrical charge density that are intermediate between aluminum oxide and silicon nitride, creating a gradual transition that reduces potential differences and eliminates PID while preserving recombination suppression.
3Reliability
If multiple passivation layers are stacked, then anti-PID performance improves, but device complexity increases
Solution Approach 1:
Rather than adding multiple complex layers, the patent introduces a single silicon oxynitride intermediary layer that performs the critical function of reducing potential differences. This single intermediate layer simplifies the overall structure compared to multiple separate functional layers while achieving the same anti-PID effect.
Solution Approach 2:
The silicon oxynitride layer performs multiple functions simultaneously: it reduces potential differences between layers, maintains carrier recombination suppression, provides optical anti-reflection properties, and protects against PID. This multi-functionality reduces the need for separate dedicated layers, thereby simplifying the overall device structure while maintaining high anti-PID 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
This configuration improves anti-PID performance by up to 81.6% to 99.0%, maintaining high conversion efficiency and light utilization rates by reducing interface recombination and preventing mobile ion migration.
Implementation Method 1
a polarization phenomenon weakening (PPW) layer and at least one silicon nitride layer Si u N v that are sequentially disposed on a rear surface of the substrate in a direction away from the substrate
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
Implementation Method 3
a photovoltaic field, in particular to a photovoltaic cell
Data Source
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AI summary
A photovoltaic cell is provided, which includes a substrate; a first passivation layer and a first anti-reflection layer disposed on a front surface of the substrate; and a second passivation layer, a PPW layer and at least one silicon nitride layer SiuNv disposed on a rear surface of the substrate; wherein 1<u/v<4, and a refractive index and thickness of which is in a range of 1.9 to 2.5 and 50 nm to 100 nm; wherein the second passivation layer includes at least one aluminum oxide layer AlxOy, wherein 0.8<y/x<1.6, and a refractive index and thickness of which is respectively in a range of 1.4 to 1.6 and 4 nm to 20 nm; wherein the PPW layer includes at least one silicon oxynitride layer SirOsNt, wherein r>s>t, and a refractive index and thickness of which is respectively in a range of 1.5 to 1.8 and 1 nm to 30 nm.