Tandem Solar Cell Structure With Gradient Doping and TCO-Free Recombination
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Solution Overview
Problem
Conventional tandem solar cells face performance limitations due to optical losses and carrier recombination at the surface and in the bulk of the silicon substrate, which affect the photoelectric conversion efficiency.
Innovation Solution
A tandem cell design is proposed, featuring a bottom cell with a semiconductor layer doped with ions, where the doping concentration gradient improves passivation and electrical performance. The intermediate layer serves as a recombination layer, eliminating the need for a TCO recombination layer, thereby reducing parasitic absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional uniform doping semiconductor layer is used in the bottom cell, then the manufacturing process is simple, but the photoelectric conversion efficiency is limited due to optical losses and carrier recombination
Solution Approach 1:
The patent applies local quality by implementing a gradient doping concentration in the semiconductor layer, where the doping concentration varies from the front surface to the back surface of the silicon substrate. Specifically, the doping concentration is lower near the front surface and higher near the back surface, creating different local electrical properties that optimize both carrier collection and passivation performance at different locations, thereby resolving the contradiction between manufacturing simplicity and photoelectric conversion efficiency
Solution Approach 2:
The patent employs parameter changes by systematically varying the doping concentration parameter throughout the semiconductor layer thickness. By changing the doping concentration from uniform to gradient distribution, and by optimizing specific parameters such as the doping concentration range (1×10^16 to 1×10^18 atoms/cm³ near the front surface and 1×10^18 to 1×10^20 atoms/cm³ near the back surface), the patent achieves improved electrical performance and reduced carrier recombination, thus enhancing photoelectric conversion efficiency
2Reliability
If a TCO recombination layer is used between top and bottom cells, then the recombination function is provided, but parasitic absorption increases reducing overall efficiency
Solution Approach 1:
The patent applies the taking out principle by removing the TCO recombination layer from the tandem cell structure. Instead of using a separate TCO layer to provide recombination functionality, the patent utilizes the gradient-doped semiconductor layer itself to perform the recombination function. This extraction of the TCO layer eliminates the parasitic absorption associated with TCO materials while maintaining the necessary recombination function through the optimized semiconductor layer design
Solution Approach 2:
The patent implements universality by making the gradient-doped semiconductor layer multi-functional. The semiconductor layer simultaneously serves as the base for the bottom cell, provides carrier recombination functionality, and acts as an optical management layer. By integrating multiple functions into a single component, the patent eliminates the need for separate TCO recombination layer, thereby reducing parasitic absorption while maintaining reliable recombination function
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
The improved tandem cell design enhances electrical and passivation performance, leading to increased photoelectric conversion efficiency and reduced parasitic absorption, thus overcoming the limitations of conventional tandem cells.
Implementation Method 1
doping concentration of doping ions in a first part of the semiconductor layer close to the substrate is less than doping concentration of doping ions in a second part of the semiconductor layer further away from the substrate than the first part
Implementation Method 2
the solar cell is a device that converts light energy from the sun into electrical energy. The solar cells generate carriers based on the photovoltaic principle
Data Source
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AI summary
Embodiments of the present disclosure relate to the technical field of photovoltaic technologies, and provide a tandem cell and a photovoltaic module. The tandem cell includes: a bottom cell, including: a substrate having a front surface and a back surface that are opposite to each other, and a semiconductor layer disposed on the back surface of the substrate and is doped with doping ions, where doping concentration of doping ions in a part of the semiconductor layer close to the substrate is less than doping concentration of doping ions in a part of the semiconductor layer away from the substrate; an intermediate layer disposed on a side surface of the semiconductor layer away from the substrate; and a top cell disposed on a side of the intermediate layer away from the substrate. In this way, performance of the tandem cell may be at least improved.