Silicon Tandem Solar Cell with Tunnel Contact
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Solution Overview
Problem
Current silicon-based solar cells have limited efficiency due to the lack of materials with different band gaps for tandem configurations, leading to insufficient power conversion and long-term stability, which restricts their commercial application.
Innovation Solution
A silicon-based tandem solar cell design featuring two diodes connected in series via a tunnel contact, with the first diode as an ultraviolet absorber and the second diode as an infrared absorber, utilizing SiGeC and SiGe layers to expand the spectral range from 300 nm to 1500 nm, enhancing electron generation and achieving higher open terminal voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single diode silicon-based solar cell is used, then the manufacturing process is simple and materials are readily available, but the power conversion efficiency is limited and cannot exceed typical commercial performance levels
Solution Approach 1:
The solar cell is divided into two separate diodes with different band gaps (first diode with Eg1 ≥ 1.4 eV and second diode with Eg2 < 1.4 eV) connected in series via a tunnel contact. This segmentation allows each diode to absorb different portions of the solar spectrum, with the first diode absorbing higher energy photons and the second diode absorbing lower energy photons, thereby increasing overall power conversion efficiency beyond what a single diode can achieve.
Solution Approach 2:
The invention employs composite material structures including SiGeC and SiGe layers in the tunnel contact region, combining materials with different properties to achieve both high efficiency and stability. The tunnel contact itself is a composite structure that enables electrical connection between the two diodes while maintaining the series configuration necessary for high voltage output.
2Reliability
If materials with different band gaps are introduced for tandem configuration, then power conversion efficiency and long-term stability improve, but the manufacturing complexity and material requirements increase
Solution Approach 1:
The invention systematically varies the band gap parameter across different layers by using SiGeC and SiGe materials with controlled germanium and carbon content. The first diode uses materials with band gap Eg1 ≥ 1.4 eV while the second diode uses materials with band gap Eg2 < 1.4 eV, creating a gradient that optimizes both stability and manufacturability by staying within the silicon-based material system.
Solution Approach 2:
The tunnel contact acts as an intermediary element between the two diodes with different band gaps. It provides the necessary electrical connection while accommodating the material transition from SiGeC/SiGe in the first diode to the silicon-based materials in the second diode, thereby enabling the tandem configuration without requiring direct junction between incompatible materials.
3Power
If two diodes are connected in series via tunnel contact, then open terminal voltage increases and efficiency exceeds 30%, but the device structure becomes more complex
Solution Approach 1:
The invention merges two diodes into a single integrated tandem structure with series connection through a tunnel contact. This combining approach allows the open terminal voltage to be the sum of the individual diode voltages (Voc = Voc1 + Voc2), achieving over 30% efficiency while maintaining a compact monolithic structure that can be produced using standard semiconductor fabrication techniques.
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 design achieves an efficiency of over 30% and a power output of 7 W for a standard 156 mm x 156 mm solar cell, significantly surpassing the typical 5 W output of commercial silicon cells, while using proven techniques and materials.
Implementation Method 1
The semiconductor component has an electrical semiconductor tunnel contact. The tunnel junction is between the first and second diodes. The two diodes are electrically connected in series via the tunnel contact.
Implementation Method 2
the first diode, particularly in the form of the partial layer, is an ultraviolet absorber
Implementation Method 3
the second diode, particularly in the form of the diode layer, is an infrared absorber
Implementation Method 4
utilizing SiGeC and SiGe layers to expand the spectral range from 300 nm to 1500 nm, enhancing electron generation
Data Source
Figure 1~2
Figure 3~4
AI summary
In one embodiment, the optoelectronic semiconductor device (1), preferably a silicon-based tandem solar cell, has a front face (10) as well as a first diode (2) and a second diode (4). The first diode (2) is located closer to the front face (10) than the second diode (4), and the diodes (2, 4) follow each other in the direction away from the front face (10). An electrical tunnel contact (3) is located between the first and the second diodes (2, 4). The semiconductor device (1) is silicon-based. The first diode (2) comprises at least one sublayer (21, 22, 23) of SiGeC. The second diode is a Si diode with a diode layer (41) of SinGe1-n, where 0 ≤ n ≤ 1.