TCO Substrate with Multi-Diameter Spherical Particles for Broadband Light Scattering
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Solution Overview
Problem
Current methods for producing textured transparent conductive oxide (TCO) layers in solar cells achieve high light diffusion only in specific wavelength ranges, requiring complex processes and resulting in reduced diffuse transmission beyond 550 nm, which limits the efficiency of photoelectric conversion.
Innovation Solution
A substrate with a diffusing layer of transparent conductive oxide (TCO) incorporating spherical particles of varying diameters, deposited in multiple populations, ensures a substantially constant TCO thickness and optimal light scattering across a wide wavelength range (350-1500 nm) by using a layer of spherical particles under the TCO, enhancing the Haze Value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single population of spherical particles is used under the TCO layer, then the manufacturing process is simple, but the light scattering efficiency is limited to specific wavelength ranges
Solution Approach 1:
The particle layer is segmented into multiple populations with different diameter ranges (first population: 0.5-5 μm, second population: 5-20 μm, third population: 20-50 μm). This segmentation allows each particle population to scatter light in specific wavelength ranges, collectively achieving broad-spectrum light scattering across 350-1500 nm while maintaining a relatively simple manufacturing process.
2Productivity
If APCVD is used to texturize the TCO surface, then light diffusion is improved in certain wavelengths, but the diffuse transmission decreases quickly below 80% from 550 nm
Solution Approach 1:
The invention changes the key parameter from surface texturing height/depth to particle diameter distribution. By controlling the diameter ranges of spherical particles in three different populations, the light scattering characteristics are optimized across different wavelength ranges. This parameter change enables broad wavelength coverage (350-1500 nm) with high diffuse transmission (>80%) maintained across the entire range.
3Productivity
If multiple manufacturing steps including plasma etching are added to achieve broad wavelength light scattering, then the light management efficiency is improved, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The spherical particle layer serves multiple functions simultaneously: (1) it acts as a scattering center for broad-spectrum light management, (2) it provides a template for conformal TCO deposition, and (3) it can be deposited in a single atomic layer deposition step. This multi-functionality achieves efficient photoelectric conversion without requiring complex multi-step processes like plasma etching of silica beads.
4Reliability
If the TCO layer thickness is increased to improve charge collection, then the electrical performance is improved, but the light transmission and scattering efficiency decreases
Solution Approach 1:
Instead of improving charge collection by increasing TCO thickness (one dimension), the invention introduces a new dimension - the spherical particle layer beneath the TCO. This particle layer provides enhanced light scattering and trapping, increasing the optical path length and improving both light absorption and charge collection efficiency without requiring increased TCO thickness, thus maintaining good light transmission.
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 solution achieves a diffuse transmission efficiency greater than 80% across a broad wavelength range, improving the photoelectric conversion efficiency of solar cells without increasing the complexity of the manufacturing process.
Implementation Method 1
The optical response of a textured conductive transparent oxide layer is, in general, translated by the 'Haze Value', that is to say the light scattering factor.
Implementation Method 2
the TCO layer, whose function is to transmit light, serves both as a charge-collecting electrode and allows light diffusion via its 'texturing'.
Implementation Method 3
deposition on the free surface of the layer of spherical particles of a layer of transparent conductive oxide with substantially constant thickness
Data Source
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AI summary
The invention relates to a substrate comprising at least one scattering film made of a transparent conductive oxide (TCO) and to a process for manufacturing such a substrate. It also relates to a solar cell comprising such a substrate. The substrate according to the invention comprises a layer of spherical particles made of a material chosen from dielectric and transparent conductive oxides, the layer being coated with a TCO film and the diameters of said spherical particles belonging to at least two populations of different diameters. The invention is applicable in particular to solar cells.