Solar Cell TCO-Metal-TCO Layers for Low-Cost Charge Collection
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Solution Overview
Problem
Existing solar cell manufacturing processes are costly due to the use of silver paste and thin transparent conductive oxides (TCO), and there is a need for more efficient charge collectors that maximize light radiation and reduce silver paste consumption.
Innovation Solution
Replace the metallization grid with a multilayer TCO-Metal-TCO (OMO) structure, comprising a transparent intermediate metal layer between two oxide layers, optimized for low resistance and high transparency, and use a new interconnection scheme to minimize silver paste usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver paste is used for metallization grid, then charge collection efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive silver paste with a multilayer TCO structure that uses cheaper materials (indium tin oxide and aluminum zinc oxide). The conductive layers are deposited as thin films rather than using thick silver paste, significantly reducing material costs while maintaining charge collection functionality.
Solution Approach 2:
The patent employs a composite multilayer structure combining different TCO materials (ITO and AZO) with complementary properties. ITO provides high conductivity while AZO offers good transparency and lower cost, creating a synergistic composite that achieves both electrical performance and cost reduction.
2Ease of manufacture
If thin TCO layer is used, then manufacturing cost is reduced, but charge collection efficiency deteriorates
Solution Approach 1:
The patent creates a multilayer composite structure where ITO and AZO layers work together. The ITO layer provides high conductivity for charge collection, while the AZO layer contributes to optical transparency and cost reduction. This composite approach maintains charge collection efficiency despite using thin layers.
Solution Approach 2:
The patent optimizes the thickness parameters of each TCO layer to achieve the right balance between conductivity and transparency. By carefully controlling layer thicknesses and doping concentrations, the structure maintains effective charge collection while minimizing material usage and cost.
3Reliability
If TCO carrier concentration is increased, then conductivity is improved, but optical transparency deteriorates
Solution Approach 1:
The patent divides the single TCO layer into multiple segmented layers with different doping concentrations and material compositions. The ITO layer can be optimized for conductivity while the AZO layer is optimized for transparency, allowing each segment to perform its specialized function without compromising the other.
Solution Approach 2:
The composite TCO structure allows combining materials with different optical and electrical properties. ITO provides high conductivity even at moderate carrier concentrations, while AZO maintains high transparency. Together they create a structure where conductivity and transparency are decoupled and independently optimized.
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
Reduces manufacturing costs, maximizes light absorption, and enhances charge collection efficiency by eliminating the need for silver paste and simplifying interconnections.
Implementation Method 1
at least a first layer made of a semiconductor material for absorbing photons from light radiation and releasing charge carriers
Implementation Method 2
said conductive layer comprises at least three overlapped layers, which are: a transparent intermediate metal layer, made of metal, and two oxide layers, made of a transparent conductive oxide
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
The present invention concerns a solar cell (1) comprising at least a first layer (3, 4', 4", 5, 6) made of a semiconductor material for absorbing photons from light radiation and releasing charge carriers, and at least one conductive layer (2), overlapping said first layer (3, 4', 4", 5, 6), adapted to allow said light radiation to enter into said solar cell (1) towards said first layer (3, 4', 4", 5, 6) and to collect the charge carriers released by said first layer (3, 4', 4", 5, 6), said solar cell (1) being characterised in that said conductive layer (2) comprises at least three overlapped layers (21, 22, 23), and specifically: - a transparent intermediate metal layer (23), made of metal, and - two transparent oxide layers (21, 22), made of a conductive oxide, said two oxide layers (21, 22) being respectively an inner oxide layer (21) and an outer oxide layer (22) surrounding said transparent intermediate metal layer (23) so as to provide a low resistance path for the electrical charges and to maximize the amount of light radiation entering the solar cell (1). The present invention concerns also a solar cells module comprising said solar cell (1).