Silicon Solar Cell Backside Texturing for Infrared Absorption
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Solution Overview
Problem
Existing silicon solar cells face challenges in maximizing the absorption of both infrared and visible light energy due to conflicting requirements for front and backside texturing, with current methods either enhancing visible light absorption at the expense of infrared or vice versa.
Innovation Solution
A semiconductor solar cell design featuring a planar front surface with a transparent layer for visible light and a textured, diffusive backside for infrared light scattering, combined with a reflecting layer to enhance infrared absorption, and optionally a stacked configuration with a gap between substrates for increased infrared reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If thick layers of white paint are applied to the backside as a diffuse reflector, then infrared absorption enhancement is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention extracts the essential function of the white paint diffuse reflector (infrared light scattering and reflection) and implements it through a simplified smooth backside surface structure, eliminating the need for thick paint layers while maintaining the infrared absorption enhancement effect.
Solution Approach 2:
The invention changes the key parameter of the backside surface from rough (textured) to smooth, which fundamentally alters the optical interaction mechanism. This parameter change enables infrared light enhancement through a different physical mechanism that does not require thick diffuse reflecting layers, thereby simplifying the device structure.
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 significantly enhances the energy conversion efficiency by achieving a large enhancement factor in infrared absorption, approaching that of thicker crystalline solar cells, while maintaining optimal visible light absorption, with the potential for a 25% higher efficiency in stacked configurations.
Implementation Method 1
A textured layer is disposed at a second surface of the silicon substrate, the textured layer being a diffusive radiation scattering layer for infrared wavelengths of radiation
Implementation Method 2
a reflecting layer disposed on the textured layer and spaced apart from the second surface by the textured layer, whereby infrared wavelengths of radiation are returned through the textured layer toward the first semiconductor substrate
Implementation Method 3
a layer transparent to visible light and infrared wavelengths is disposed at the first surface. This layer is internally reflective to infrared wavelengths of radiation scattered within the first semiconductor substrate
Data Source
AI summary
The absorption coefficient of silicon for infrared light is very low and most solar cells absorb very little of the infrared light energy in sunlight. Very thick cells of crystalline silicon can be used to increase the absorption of infrared light energy but the cost of thick crystalline cells is prohibitive. The present invention relates to the use of less expensive microcrystalline silicon solar cells and the use of backside texturing with diffusive scattering to give a very large increase in the absorption of infrared light. Backside texturing comprises a plurality of cusped features providing diffusive scattering. Constructing the solar cell with a smooth front surface results in multiple internal reflections, light trapping, and a large enhancement of the absorption of infrared solar energy.