Thin Light-Trapping Films for Higher Solar Absorption
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Solution Overview
Problem
Conventional photovoltaic devices suffer from inefficient light trapping and coupling, leading to significant energy loss due to the random nature of light interactions with microstructures and high reflection losses from surfaces with large refractive indices, which limits the absorption of sunlight and subsequent electricity generation.
Innovation Solution
A light harvesting system with a layered structure featuring a focusing array and a photoresponsive layer, where light input ports are strategically aligned with light collecting elements to inject light at oblique angles, enhancing light coupling and path length within the layer through total internal reflection, thereby improving absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active layer thickness is increased to improve light absorption, then the absorption efficiency is improved, but the manufacturing cost increases due to higher material consumption
Solution Approach 1:
The patent introduces light-trapping microstructures (pyramids, trenches, porous layers) on the surface of the active layer to extend the optical path length in the vertical dimension. This allows light to interact with the active layer multiple times without increasing the physical thickness, thereby maintaining high absorption efficiency while using less semiconductor material.
Solution Approach 2:
The patent employs curved or non-planar surface structures such as pyramidal shapes and porous networks that scatter and trap light through multiple reflections. These curved geometries increase the effective light path length within the thin active layer, improving absorption without requiring increased material thickness.
2Loss of energy
If conventional light trapping methods are used with random pyramidal microstructures, then some light scattering is achieved, but a large portion of incident light is lost due to random secondary interactions and reflection
Solution Approach 1:
The patent divides the light-trapping function into multiple specialized layers: a textured entry surface for initial scattering, a dedicated light-trapping layer with controlled microstructures for multiple reflections, and a porous absorption layer. This segmentation allows each layer to perform its function efficiently, reducing random light loss while maintaining manageable structural complexity.
Solution Approach 2:
The patent introduces a transparent light-trapping layer as an intermediary between the entry surface and the active absorption layer. This intermediate layer contains controlled microstructures that scatter and trap light before it reaches the active layer, reducing direct reflection losses and improving coupling efficiency without requiring the active layer itself to be highly complex.
3Quantity of substance
If the active layer is made thinner to reduce material cost, then material consumption decreases, but light absorption efficiency deteriorates due to insufficient interaction length
Solution Approach 1:
The patent compensates for reduced physical thickness by introducing microstructural features that extend the optical path length in the vertical dimension. Light-trapping structures such as pyramids, trenches, and porous networks cause multiple internal reflections, effectively increasing the interaction length between light and the thin active layer without requiring additional material thickness.
Solution Approach 2:
The patent employs porous structures within the active layer or adjacent layers that increase the surface area and create multiple light-matter interaction sites. The porous network traps light through repeated reflections and refractions at the pore interfaces, enabling efficient absorption in thin films with reduced material consumption.
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 system achieves enhanced light absorption and energy conversion efficiency by ensuring multiple passages of light through the photoresponsive layer, reducing energy loss and increasing photocurrent generation while using thinner, less expensive semiconductor materials.
Implementation Method 1
Each light collecting element is configured to collect light from a larger area and focus the incident light onto a substantially smaller focal area
Implementation Method 2
photovoltaic solar cells or light detectors employ an active photoresponsive layer that absorbs at least a portion of the electromagnetic spectrum of the light and generates charge carriers due to the photovoltaic effect
Implementation Method 3
During light trapping, some scattered light can be trapped in the active layer of the solar photovoltaic device by means of TIR which can even allow for the multiple passage of a portion of solar rays through the active layer
Data Source
AI summary
A method of making a light converting optical system is described. The method includes providing a layered light trapping structure comprising a first optical layer with a plurality of linear grooves having triangular cross-sections for reflecting and deflecting light through total internal reflection and refraction. A diffuse reflector, made from a thin sheet of diffuse reflective material, is placed parallel to the first optical layer. A light converting film, positioned between the first optical layer and the diffuse reflector, contains an active layer with first and second light converting semiconductor materials of different bandgaps. The thickness of the active layer is below the minimum required to absorb all visible spectrum light in a single passage. The method further involves providing a light source and positioning the layered light trapping structure to receive energy from the light source.