Optically-Thin Chalcogenide Solar Cells Light Trapping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solar cells face efficiency limitations due to incomplete absorption and increased dark current as cell thickness decreases, which hinders the performance of thin-film photovoltaic devices, especially in radiative limits, while also being costly and less robust compared to crystalline silicon technologies.
Innovation Solution
The development of optically-thin solar cells incorporating advanced light trapping structures, band gap engineering, and thin-film device fabrication, including a multijunction structure with a back reflective coating and top scattering antireflection structure, enhances radiation tolerance and reduces material costs by increasing the optical path length of incident light within the absorber layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If cell thickness is decreased to reduce material costs and dark current, then dark current decreases and open circuit voltage increases, but absorption completeness decreases and short circuit current decreases
Solution Approach 1:
The patent introduces light trapping structures that redirect light from vertical propagation to lateral propagation within the absorber layer, effectively increasing the optical path length without increasing the physical thickness of the cell. This dimensional transformation of light transport enables thin-film cells to achieve absorption levels comparable to thick cells while maintaining the advantages of reduced material usage and lower dark current.
Solution Approach 2:
The patent employs intermediate optical structures including front surface texturing, dielectric mirror stacks, and rear surface texturing that act as mediators to enhance light absorption. These intermediate structures trap and redirect photons multiple times through the thin absorber layer, enabling complete absorption without requiring increased cell thickness, thus resolving the contradiction between thinness and absorption completeness.
2Productivity
If conventional light trapping structures are used in thin-film cells, then absorption is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent utilizes parameter changes in the dielectric mirror stack design, specifically adjusting the thickness and refractive index of alternating dielectric layers to achieve high reflectivity at specific wavelengths. By optimizing these parameters, the structure achieves superior light trapping and absorption efficiency while maintaining compatibility with existing thin-film manufacturing processes, thus improving absorption without proportionally increasing manufacturing complexity.
3Quantity of substance
If optically-thin structures are employed to reduce material costs, then material usage decreases, but radiation tolerance may be compromised
Solution Approach 1:
By transforming light transport from vertical to lateral propagation through optical trapping structures, the patent enables thin-film cells to achieve absorption equivalent to thick cells. This means radiation tolerance can be maintained at thin-film thickness levels because the effective optical path length is extended without increasing physical thickness, allowing thin cells to withstand radiation better while using less material.
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 approach enhances the efficiency of thin-film solar cells, matching or exceeding the performance of optically thick devices, while offering increased radiation tolerance and reduced material costs, achieving high-voltage ultra-thin diode performance and improved photocurrent generation.
Implementation Method 1
a back reflective coating structure
Implementation Method 2
a top scattering antireflection (AR) structure
Implementation Method 3
photovoltaic solid state semiconductor devices, commonly known as solar cells, convert sunlight into electrical power by generating both a current and a voltage upon illumination
Data Source
AI summary
A photovoltaic device comprises a back reflective coating structure to provide back scattering of light that passes through the photovoltaic device, an absorber structure containing chalcogenide materials, and a top scattering antireflective structure deposited on the top subcell. Illustratively, a multi-junction structure comprises a bottom subcell deposited on the back reflective coating structure, the bottom subcell having a lower band gap, higher index material embedded therein, to provide lateral propagation of light that passes through the photovoltaic device, and a top subcell deposited on the bottom subcell. The multi-junction structure can comprise chalcogenide materials, in which case the top subcell is embedded with an intermediate band gap absorber material.