Back-Contact Solar Cell Layout to Reduce Shading and Recombination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solar cells have a grid line structure on the front side that reduces light receiving area and increases electron-hole pair recombination, leading to decreased photoelectric conversion efficiency.
Innovation Solution
A solar cell design with alternating emitter and back surface field regions on the back side, where the emitter is connected to the positive electrode, eliminating the grid line on the front side and using a tunnel oxide layer and phosphorus doped polysilicon layer to reduce recombination, along with specific dimensions and spacings for optimal grid line density and electrode placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grid line structure is used on the front side of the solar cell, then current collection is improved, but the light receiving area is reduced and photoelectric conversion efficiency decreases
Solution Approach 1:
The patent inverts the conventional solar cell structure by moving the emitter and grid line structure from the front side to the back side. The back side now contains alternating emitter regions and back surface field regions, while the front side becomes fully active for light reception without any grid lines, resolving the contradiction between current collection and light receiving area.
2Ease of manufacture
If conventional diffusion is used to form the diffusion layer, then manufacturing is simplified, but the recombination rate of electron-hole pairs increases and efficiency is limited
Solution Approach 1:
The patent applies local quality by creating distinct regions with different properties on the back side: emitter regions with boron-doped monocrystalline silicon for current collection, and back surface field regions with tunnel oxide and phosphorus-doped polysilicon for reducing recombination. This localized differentiation allows each region to optimize its function while maintaining overall manufacturing feasibility.
3Reliability
If the emitter is placed on the front side with grid lines, then current collection is improved, but the photoelectric conversion efficiency decreases due to shading loss
Solution Approach 1:
The patent transitions the emitter structure from the two-dimensional front surface to the back surface, utilizing the third dimension (depth) to relocate functional elements. This dimensional change allows the front surface to be fully dedicated to light absorption while the back surface handles current collection, eliminating the trade-off between shading loss and current collection.
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 increases the frontal light receiving area, reduces electron-hole pair recombination, and enhances the photoelectric conversion efficiency of the solar cell.
Implementation Method 1
The tunneling effect of the tunnel oxide layer allows electrons to pass through but not holes
Implementation Method 2
the phosphorus doped polysilicon forms a passivated contact, thus reducing the recombination rate of electron-hole pairs
Implementation Method 3
The present application relates to the field of photovoltaic technology
Data Source
AI summary
In a solar cell, the back surface of a substrate thereof is provided with alternately distributed emitter zones and back surface field zones. An emitter is formed in each emitter zone, and the emitters are made of boron-doped monocrystalline silicon. A back surface field is formed in each back surface field zone; the back surface fields comprise tunneling oxide layers and polycrystalline silicon layers in stacked distribution, the polycrystalline silicon layers being made of phosphorus-doped polycrystalline silicon, and the tunneling oxide layers being located between a polycrystalline silicon layer and a polycrystalline silicon layer. Positive electrodes are electrically connected to the emitters, and negative electrodes are electrically connected to the back surface fields. In the described solar cell, the light-receiving area of the front surface can be expanded and the recombination rate of electron-hole pairs can be reduced, thereby effectively improving the photoelectric conversion efficiency of the solar cell.