Silicon Tandem Solar Cell Tunnel Junction With Abrupt Doping Interface
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Solution Overview
Problem
Tandem photovoltaic devices with crystalline silicon cells face low tunneling efficiency and high overall series resistance due to slowly changed diffusion interfaces, which reduce effective doping concentration and broaden tunneling distances.
Innovation Solution
Incorporating an intermediate dielectric layer between the upper and lower crystalline silicon layers with doping concentrations greater than or equal to 1018 cm−3, and a band gap width of at least 3 eV, to form an abrupt doping interface structure, thereby improving tunneling efficiency and reducing series resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an intermediate layer is introduced between the upper and lower crystalline silicon layers to prevent doping element diffusion, then the interface sharpness is improved, but the device complexity increases
Solution Approach 1:
An intermediate layer comprising a first intermediate layer and a second intermediate layer is introduced between the upper and lower crystalline silicon layers. The first intermediate layer has a doping concentration lower than both adjacent crystalline silicon layers, while the second intermediate layer has a doping concentration higher than both adjacent crystalline silicon layers. This intermediate structure prevents doping element diffusion and sharpens the interface between the upper and lower crystalline silicon layers, thereby resolving the technical contradiction.
2Reliability
If the tunnel junction thickness is reduced to achieve higher recombination rate, then the tunneling efficiency is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the thickness of the intermediate layer to be between 0.1 to 5 nm and the doping concentrations of the crystalline silicon layers to be greater than or equal to 10^18 cm^-3. By precisely controlling these parameters, the patent achieves high tunneling efficiency while maintaining feasible manufacturing precision requirements.
3Reliability
If the doping concentration at the interface is increased to improve tunneling efficiency, then the series resistance is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent implements local quality by creating regions with different doping concentrations: the first intermediate layer has low doping concentration, the upper and lower crystalline silicon layers have high doping concentrations (≥10^18 cm^-3), and the second intermediate layer has high doping concentration. This localized doping strategy improves tunneling efficiency and reduces series resistance while managing manufacturing complexity through targeted doping in specific regions.
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 configuration enhances tunneling efficiency, increases peak tunneling current, and decreases overall series resistance by facilitating energy level degeneracy and effective doping concentration alignment at the interfaces.
Implementation Method 1
Incorporating an intermediate dielectric layer between the upper and lower crystalline silicon layers with doping concentrations greater than or equal to 1018 cm−3, and a band gap width of at least 3 eV, to form an abrupt doping interface structure
Implementation Method 2
A tunnel junction is provided with a strong transmission and recombination capability and its thickness required to achieve a higher recombination rate is relatively thin. Therefore, the tunnel junction is usually used to connect each cell unit in series in the tandem photovoltaic devices.
Data Source
AI summary
A tandem photovoltaic device and production method. The tandem photovoltaic device includes: an upper battery cell and a lower battery cell, and a tunnel junction located between the upper battery cell and the battery cell; the lower battery is a crystalline silicon cell; the tunnel junction includes: an upper crystalline silicon layer, a lower crystalline silicon layer and an intermediate layer located between the upper crystalline silicon layer and the lower crystalline silicon layer; the upper crystalline silicon layer, the lower crystalline silicon layer and the intermediate layer are in direct contact, and the doping types of the upper crystalline silicon layer and the lower crystalline silicon layer are opposite; the doping concentration of the upper crystalline silicon layer at the interface with the intermediate layer and the doping concentration of the lower crystalline silicon layer at the interface with the intermediate layer are greater than or equal to 1018 cm−3.