Tandem Cell Bottom-Cell Texturing for Optical Loss Reduction
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Solution Overview
Problem
Tandem solar cells suffer from significant optical loss and poor efficiency due to the combination of a top cell with a wide bandgap and a bottom cell with a narrow bandgap, limiting their performance.
Innovation Solution
The tandem cell design includes a bottom cell with a substrate featuring a first textured surface with larger protrusion structures and a micro textured surface with smaller protrusion structures, along with a conformal composite layer and top cell layers that enhance light reflection and reduce minority carrier recombination, ensuring uniform film layers and avoiding short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a tandem cell combines a top cell with wide bandgap and a bottom cell with narrow bandgap to break the single junction efficiency limit, then the theoretical photovoltaic conversion efficiency is improved, but significant optical loss occurs resulting in poor actual cell efficiency
Solution Approach 1:
The patent applies surface texturing with protrusion structures to the substrate and conductive layer surfaces. These curved/rounded protrusion structures enhance light trapping and reflection, reducing optical loss by increasing the optical path length and improving light absorption in the tandem cell structure.
Solution Approach 2:
The patent modifies surface parameters by creating textured surfaces with specific protrusion structures at different scales. The substrate has a first textured surface with first protrusion structures, and the doped conductive layer has a micro textured surface with micro protrusion structures. These parameter changes in surface morphology reduce optical loss and improve light utilization.
2Productivity
If textured surfaces with protrusion structures are added to reduce optical loss, then light utilization is improved, but the device structure becomes more complex
Solution Approach 1:
The patent segments the texturing into multiple levels: the substrate has a first textured surface with first protrusion structures, while the doped conductive layer has a micro textured surface with micro protrusion structures. This segmentation allows each layer to be optimized independently for light management while maintaining overall structural functionality.
Solution Approach 2:
Different regions and layers have different texturing characteristics. The substrate surface has first protrusion structures, the doped conductive layer has micro protrusion structures, and the composite layer is conformal to the micro textured surface. This local quality variation optimizes light interaction at different interfaces without requiring complex overall restructuring.
3Reliability
If multiple layers including composite layer and conformal structures are added to reduce recombination and avoid short circuits, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The composite layer is formed conformally on the micro textured surface of the doped conductive layer before forming the top cell. This preliminary action of creating the conformal composite layer structure early in the manufacturing process establishes a foundation that guides subsequent layer formation, ensuring proper alignment and reducing recombination while simplifying later manufacturing steps.
Solution Approach 2:
The composite layer merges the textured surface structure with the top cell formation process. By making the composite layer conformal to the micro textured surface, the patent combines light management functionality with structural integrity and electrical isolation functions in a single integrated layer, reducing the need for separate components.
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 design improves light utilization and photovoltaic conversion efficiency by enhancing light reflection and reducing recombination, leading to improved open circuit voltage and filling factor.
Implementation Method 1
The tandem cell design includes a bottom cell with a substrate featuring a first textured surface with larger protrusion structures and a micro textured surface with smaller protrusion structures, along with a conformal composite layer and top cell layers that enhance light reflection
Implementation Method 2
The solar cell uses the photovoltaic effect to generate carriers, which are then extracted using electrodes to be effectively utilized as electrical energy
Implementation Method 3
the bottom cell further includes a tunneling dielectric layer formed on the second side
Data Source
AI summary
The tandem cell includes a bottom cell including a substrate. The substrate has a first side and a second side, the first side has a first textured surface including at least one first protrusion structure. The bottom cell further includes a tunneling dielectric layer and a doped conductive layer. A surface of the doped conductive layer has a micro textured surface including at least one micro protrusion structure, and the micro protrusion structure is smaller than the first protrusion structure. The tandem cell further includes a composite layer conformal to the micro textured surface. The tandem cell further includes a top cell formed on the composite layer. The top cell includes a first transport layer, a perovskite substrate, a second transport layer, a transparent conductive layer, and an anti-reflection layer stacked sequentially. The first transport layer is conformal to the micro textured surface.