Thin-Film Photovoltaic Backside Electrodes for Large-Area Cells
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Solution Overview
Problem
Existing thin film photovoltaic devices face limitations in expanding cell size due to low conductivity of transparent electrodes, leading to resistive losses and chemical degradation issues with monolithic interconnections, particularly in semi-transparent or bifacial devices.
Innovation Solution
The introduction of via-hole contacts protected by an insulating layer for supporting electrodes, allowing contact with the lower electrode and enabling the use of two supporting electrodes on the backside to increase conductivity without shading losses, while preventing chemical degradation of the light-absorbing material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If monolithic series interconnection is used to expand device area, then current limitation and resistive loss are addressed, but chemical degradation occurs due to direct contact between light absorbing layer and electrode
Solution Approach 1:
An insulating layer is introduced as an intermediary between the light absorbing layer and the electrode. This layer prevents direct chemical contact while allowing electrical connection through via-holes, thereby eliminating chemical degradation pathways while maintaining the monolithic interconnection architecture for expanded device area
Solution Approach 2:
The continuous electrode structure is segmented by introducing via-holes that penetrate through the insulating layer. This segmentation allows selective electrical contact points while maintaining insulation elsewhere, enabling current collection without creating continuous chemical degradation paths across the entire electrode interface
2Loss of energy
If transparent electrode conductivity is increased to expand cell width, then resistive loss is reduced, but transparency is compromised
Solution Approach 1:
A composite structure is formed by combining the transparent electrode with an insulating layer and metal supporting electrode. The transparent electrode maintains its transparency function while the metal supporting electrode provides high conductivity through the insulating layer via via-holes, achieving both low resistive loss and high transparency through material composition rather than relying on a single material to fulfill both functions
3Device complexity
If cell size is expanded to reduce manufacturing complexity, then production efficiency increases, but voltage increases making inverter compatibility difficult
Solution Approach 1:
The electrical connection is extended into the vertical dimension by introducing via-holes that penetrate through the insulating layer. This allows the supporting electrode to contact the electrode through the thickness of the device, enabling large area collection without requiring excessive series connections, thus managing voltage levels while maintaining manufacturing simplicity
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 solution significantly expands the dimensions of thin film photovoltaic cells, reduces voltage, and makes them compatible with conventional inverters, while minimizing chemical degradation and transparency loss, allowing for larger, efficient, and stable semi-transparent or bifacial devices.
Implementation Method 1
a solar cell or photovoltaic cell is a solid-state device (semiconductor) that converts the energy of incident sunlight directly into electricity via the photovoltaic effect
Implementation Method 2
The P2 structure creates a region in which there is direct contact between the light absorbing layer and the upper electrode, giving rise to a possible mechanism of chemical degradation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention concerns thin film photovoltaic devices, containing a substrate, a first transparent conductive electrode, an absorber of electromagnetic radiation between two selective semiconductors and a second conductive electrode which form the final structure of the device. The limited conductivity of transparent electrodes represents a limitation in the design of large-area thin-film photovoltaic devices. The present invention teaches the deposition of one or two metal supporting electrodes (8) on the side of the cell not directly exposed to light, using insulating layers (7) which prevent direct contact between the electrodes (4, 6) and the absorbing layer (5), and allows the supporting electrodes (8) to be overlapped for minimizing shading, if required. The manufacturing scheme of the photovoltaic device with one or two supporting electrodes (8) represents a technological advancement to enlarge the size of large area cells, decrease the shading provided by the collection grids and provide a new interconnection scheme that can mitigate some degradation mechanisms.