Thin Light-Trapping Photovoltaic Layers for Oblique Light Coupling
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Solution Overview
Problem
Conventional photovoltaic devices suffer from inefficiencies in light trapping and coupling, leading to significant energy loss due to the random nature of light interactions with microstructures and high refractive indices, which result in poor light absorption and high production costs.
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.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional light trapping microstructures are used, then light absorption is improved, but light scattering and energy loss increase due to random interactions
Solution Approach 1:
The patent divides the light trapping function into two distinct components: (1) a light scattering layer with specific microstructures that performs controlled scattering, and (2) a separate photovoltaic active layer that performs light absorption. This segmentation allows each component to be optimized independently, preventing the random scattering problems that occur when scattering and absorption are combined in conventional single-layer structures.
Solution Approach 2:
The patent introduces a light scattering layer as an intermediary component between the incident light and the photovoltaic active layer. This intermediary performs controlled light scattering to increase the optical path length, then directs the scattered light into the active layer for absorption. This mediator approach eliminates the random scattering losses that occur in conventional direct light-trapping structures.
2Use of energy by moving object
If thick photovoltaic layers are used to improve light absorption, then absorption efficiency increases, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary light scattering action in the scattering layer before light enters the photovoltaic active layer. By pre-scattering the light to increase its path length and improve coupling, the system achieves high absorption efficiency in thinner active layers, thereby reducing the amount of expensive photovoltaic material required and lowering manufacturing costs.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a separate scattering layer with specific microstructural parameters (size, shape, distribution). This parameter change allows the photovoltaic active layer to be made thinner while maintaining or improving absorption efficiency, thus reducing material cost without sacrificing performance.
3Use of energy by moving object
If high refractive index materials are used to improve light coupling, then light coupling efficiency increases, but reflection losses increase
Solution Approach 1:
The patent introduces a light scattering layer as an intermediary between the air interface and the high refractive index photovoltaic material. This intermediary layer with lower refractive index reduces the abrupt refractive index mismatch, thereby minimizing Fresnel reflection losses while still enabling effective light coupling into the high-index active layer through the scattering mechanism.
Solution Approach 2:
The patent optimizes the refractive index parameter of the light scattering layer to be intermediate between air and the photovoltaic material. This parameter optimization reduces reflection losses at interfaces while maintaining effective light coupling, solving the contradiction between using high-index materials for coupling efficiency and avoiding reflection losses.
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 configuration significantly improves light absorption and energy conversion efficiency by ensuring multiple passages of light through the photoresponsive layer, reducing energy loss and potentially allowing for thinner, less expensive photovoltaic 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
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
Each light input port is configured to communicate the incident light into the photoresponsive layer at a sufficiently oblique angle so as to increase the optical path of the light rays through the designated layer
Data Source
AI summary
The present invention relates to a method of making a light converting optical system. The method involves providing a first optical layer having a microstructured front surface comprising an array of linear grooves that reflect first light rays using total internal reflection and deflect second light rays using refraction. A thin sheet of reflective light scattering material is positioned parallel to the first optical layer. A second optical layer is provided with a microstructured front surface. A continuous photoabsorptive film layer comprising a light converting semiconductor material is positioned between the first optical layer and the reflective material, with a thickness less than the minimum thickness required for absorbing all light traversing through the film layer. The method further involves providing a light source and positioning the second optical layer on the light path between the light source and the photoabsorptive film layer.