Epitaxial Si Thin-Film Solar Cell Module for Cost Reduction
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Solution Overview
Problem
The high cost and limited efficiency of existing solar cells due to the use of thick crystalline-Si substrates, which increase manufacturing costs and result in reduced short-circuit current and open-circuit voltage, are addressed by developing a double-sided heterojunction solar cell module with a multilayer structure epitaxially grown on a low-cost metallurgical-Si substrate, allowing for substrate reuse and improved passivation.
Innovation Solution
A double-sided heterojunction solar cell module is fabricated with a multilayer structure including a heavily doped amorphous Si emitter, a lightly doped crystalline Si base layer, and a back-surface-field layer, epitaxially grown on a metallurgical-Si substrate, which is then transferred to a glass cover and laminated with adhesive polymer layers for enhanced efficiency and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick crystalline-Si substrate is used in solar cells, then the structural stability and light absorption are improved, but the manufacturing cost increases significantly and the short-circuit current and open-circuit voltage are reduced
Solution Approach 1:
The solar cell structure is segmented into multiple functional layers: a thin crystalline-Si absorber layer (5-50 μm) epitaxially grown on a metallurgical-Si substrate, with front and back contact layers, passivation layers, and reflective layers. This segmentation allows each layer to perform its specific function optimally while reducing overall material consumption and cost.
Solution Approach 2:
The patent changes the thickness parameter of the crystalline-Si absorber layer from traditional thick substrates (200-300 μm) to thin films (5-50 μm), and modifies the doping concentration parameters in different layers to optimize electrical properties. This parameter optimization reduces material usage while maintaining or improving device performance.
2Stability of the object's composition
If a thick crystalline-Si substrate is used, then the structural integrity is maintained, but the open-circuit voltage and short-circuit current are reduced
Solution Approach 1:
Different regions of the solar cell are given different local properties: the front surface has heavy doping and passivation for high open-circuit voltage, the back surface has reflective layers and contact structures for high short-circuit current, while the bulk absorber layer is optimized for light absorption. This local optimization maximizes power output without requiring thick substrates.
Solution Approach 2:
The solar cell employs composite material structures including epitaxial crystalline-Si layers grown on metallurgical-Si substrates, combined with amorphous-Si passivation layers, transparent conductive oxide layers, and metal reflective layers. This composite structure achieves both structural integrity and high electrical performance.
3Ease of manufacture
If a metallurgical-Si substrate is used instead of crystalline-Si substrate, then the manufacturing cost is reduced and substrate reuse is enabled, but the light absorption efficiency and carrier collection are worsened
Solution Approach 1:
The patent extracts only the necessary function of the substrate (mechanical support and seed for epitaxial growth) from the expensive crystalline-Si material, using inexpensive metallurgical-Si instead. The light absorption function is then performed by the thin epitaxial crystalline-Si absorber layer grown on top, separating the support function from the optical function.
Solution Approach 2:
The epitaxial crystalline-Si absorber layer acts as an intermediary between the metallurgical-Si substrate and the optical/electrical functions. It provides the necessary crystal structure for efficient light absorption and carrier collection while being grown on the low-cost metallurgical-Si substrate, which serves only as a mechanical support.
4Ease of manufacture
If the crystalline-Si substrate thickness is reduced, then the manufacturing cost decreases and substrate reuse becomes possible, but the structural stability and light absorption are compromised
Solution Approach 1:
The patent uses thin-film technology to create a flexible, multi-layer structure where each thin layer contributes specific functionality. The thin crystalline-Si absorber layer (5-50 μm) provides structural stability sufficient for device operation while enabling substrate reuse, demonstrating that thin films can replace thick rigid substrates.
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 approach reduces manufacturing costs and improves solar cell efficiency by minimizing substrate consumption, enabling higher open-circuit voltage and short-circuit current while allowing for the reuse of the metallurgical-Si substrate, thus providing a cost-effective and high-efficiency solar cell solution.
Implementation Method 1
A solar cell converts light into electricity using the photoelectric effect
Implementation Method 2
epitaxially grown on a low-cost MG-Si wafer
Data Source
AI summary
One embodiment of the present invention provides a double-sided heterojunction solar cell module. The solar cell includes a frontside glass cover, a backside glass cover situated below the frontside glass cover, and a number of solar cells situated between the frontside glass cover and the backside glass cover. Each solar cell includes a semiconductor multilayer structure situated below the frontside glass cover, including: a frontside electrode grid, a first layer of heavily doped amorphous Si (a-Si) situated below the frontside electrode, a layer of lightly doped crystalline-Si (c-Si) situated below the first layer of heavily doped a-Si, and a layer of heavily doped c-Si situated below the lightly doped c-Si layer. The solar cell also includes a second layer of heavily doped a-Si situated below the multilayer structure; and a backside electrode situated below the second layer of heavily doped a-Si.