Multilayer Solar Cell Passivation for Reflectivity and Voltage Tradeoffs
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Solution Overview
Problem
Existing solar cells have high reflectivity due to the use of silicon nitride passivation layers with high refractive indices, leading to low open-circuit voltage, short-circuit current, and photoelectric conversion rates.
Innovation Solution
A solar cell design featuring a dielectric first passivation layer, a first SiuNv material with a refractive index range of 1.3 to 1.7 for strong long-wave light absorption, and a SirOs material with a refractive index range of 1.9 to 3.2 for strong short-wave light absorption, reducing reflectivity and enhancing light absorption across different wave bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride passivation layer with high refractive index is used, then the passivation effect is improved, but the reflectivity of incident light increases
Solution Approach 1:
The single-layer high refractive index passivation layer is segmented into a multi-layer structure consisting of a first passivation layer (AlxOy, refractive index 1.6-1.8), a second passivation layer (SiuNv, refractive index 1.8-2.0), and a third passivation layer (SirOs, refractive index 1.4-1.6). This segmentation creates a gradual refractive index transition from the substrate to the external environment, reducing light reflection while maintaining passivation effectiveness.
Solution Approach 2:
The patent employs composite materials with different refractive indices arranged in specific layers. The combination of AlxOy, SiuNv, and SirOs materials creates an optical gradient structure that functions as both a passivation layer and an anti-reflection coating, simultaneously achieving electrical passivation and optical optimization.
2Reliability
If a high refractive index passivation layer is used, then the passivation effect is improved, but the photoelectric conversion rate decreases
Solution Approach 1:
The passivation structure is segmented into multiple layers with progressively optimized refractive indices. The third passivation layer (SirOs) with the lowest refractive index (1.4-1.6) serves as the outermost layer to minimize reflection of incident light, while the first and second layers provide strong passivation, collectively enhancing both passivation effect and light absorption.
Solution Approach 2:
The patent optimizes the refractive index parameters of each passivation layer to achieve an ideal gradient distribution. By controlling the composition ratios (x, y, u, v, s, r) and corresponding refractive indices of different materials, the structure achieves maximum light transmission while maintaining effective carrier passivation.
3Reliability
If the refractive index of the passivation layer is increased, then the passivation effect is improved, but the open circuit voltage decreases
Solution Approach 1:
The passivation function is segmented between different layers: the first passivation layer (AlxOy) and second passivation layer (SiuNv) with higher refractive indices provide strong electrical passivation and field effect, while the third passivation layer (SirOs) with lower refractive index optimizes optical properties. This segmentation allows each layer to specialize in either electrical or optical functions.
Solution Approach 2:
Different regions of the passivation structure have different local properties optimized for their specific functions. The inner layers near the substrate have higher refractive indices for electrical passivation, while the outer layer has lower refractive index for light absorption, achieving local optimization of both electrical and optical 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 design improves open-circuit voltage, short-circuit current, filling factor, and photoelectric conversion rate by optimizing light absorption and reducing reflectivity, potentially making solar cells appear grayish blue or black, suitable for dark-colored modules.
Implementation Method 1
The passivation structure on the surface of the solar cell has a relatively high refractive index... However, the existing solar cell with the passivation layer still has relatively high reflectivity for the incident light
Implementation Method 2
A solar cell structure with a dielectric first passivation layer, a first SiuNv passivation layer with a refractive index range of 1.3 to 1.7, and a SirOs passivation layer with a refractive index range of 1.9 to 3.2, optimized by adjusting atomic ratios to enhance light absorption and reduce reflectivity
Implementation Method 3
a tunneling oxide layer and a doped conductive layer sequentially formed on the back surface of the substrate and in a direction away from the back surface, the doped conductive layer and the substrate are doped to have a same conductivity type
Implementation Method 4
The solar cell generally has a passivation structure on a surface of the solar cell in order to inhibit a recombination of carriers on the surface
Data Source
AI summary
A solar cell includes a substrate having a front surface and a back surface opposite to the front surface; a first passivation layer, a second passivation layer and a third passivation layer sequentially formed on the front surface of the substrate and in a direction away from the substrate; where the first passivation layer includes a dielectric material; the second passivation layer includes a first SiuNv material, and a value of v/u is 1.3≤v/u≤1.7; and the third passivation layer includes a SirOs material, and a value of s/r is 1.9≤s/r≤3.2; and a tunneling oxide layer and a doped conductive layer sequentially formed on the back surface of the substrate and in a direction away from the back surface; the doped conductive layer and the substrate are doped to have a same conductivity type.