Light Scattering Structures for Thin-Film Solar Cells
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Solution Overview
Problem
III-V solar cells are costly due to high growth expenses, limiting their application to high-value markets, and there is a need for methods to reduce film thickness and costs to make them suitable for conventional markets.
Innovation Solution
A method involving surface roughening of a Group III-V element layer using HCl gas in a reactor, combined with hydride vapor phase epitaxy, to create a textured surface that allows for thinner solar cell production without efficiency loss, including the use of HCl with liquids to form intermediate gases for layer deposition and the addition of reflective metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thickness of III-V solar cells is reduced to lower costs, then manufacturing cost decreases, but light absorption efficiency deteriorates
Solution Approach 1:
The patent applies surface texturing to create a curved, non-planar back surface of the solar cell. This curvature increases the optical path length of light traversing the cell and enhances light trapping, allowing thinner cells to maintain high absorption efficiency. The textured surface creates multiple internal reflections that extend the effective light path without requiring increased cell thickness.
Solution Approach 2:
The invention transitions from a planar two-dimensional surface to a three-dimensional textured surface by creating pyramidal or random texturing patterns. This dimensional change increases the surface area and creates angular variations that trap light more effectively, compensating for the reduced cell thickness and maintaining absorption efficiency in thinner structures.
2Reliability
If conventional growth methods are used for III-V solar cells, then material quality is maintained, but manufacturing cost increases
Solution Approach 1:
The patent employs Hydride Vapor Phase Epitaxy (HVPE) which utilizes different chemical parameters and reaction conditions compared to conventional methods. By changing the vapor phase chemistry and deposition parameters, HVPE achieves high growth rates with excellent material quality, significantly reducing manufacturing time and cost while maintaining the required crystal quality for efficient solar cells.
Solution Approach 2:
The invention uses vapor phase transport of precursors through controlled gas flow systems. The HVPE process utilizes hydrogen carrier gases to transport metal halide precursors to the substrate, enabling precise control of deposition rates and composition. This pneumatic delivery system allows for scalable, cost-effective production while maintaining high material quality through controlled vapor phase reactions.
3Reliability
If surface roughening is applied to enhance light scattering, then light trapping improves, but surface quality deteriorates
Solution Approach 1:
The patent performs surface texturing during the epitaxial growth process itself, rather than as a separate post-processing step. By incorporating the texturing action into the growth phase, the rough surface structure is created simultaneously with the crystalline layer formation, ensuring that the texture features are integrated into the crystal lattice and maintain high structural quality without introducing surface defects or contamination from subsequent mechanical or chemical etching processes.
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 reduces the thickness of III-V solar cells while maintaining efficiency, enabling their use in broader market applications by incorporating light scattering structures that enhance absorbance and current density without significant loss in performance.
Implementation Method 1
contacting a surface of a first layer that includes a Group III element and a Group V element with a gas that includes HCl, where the contacting results in a roughening of the surface
Implementation Method 2
contacting HCL with a first liquid positioned in a first boat, resulting in the forming of a first intermediate gas
Implementation Method 3
contacting HCl with a second liquid positioned in a second boat, resulting in the forming of a second intermediate gas
Implementation Method 4
the wafer may be maintained at a temperature between 650° C. and 800° C.
Implementation Method 5
Light scattering structures for thin-film solar cells
Data Source
AI summary
The present disclosure relates to a method that includes contacting a surface of a first layer that includes a Group III element and a Group V element with a gas that includes HCl, where the first layer is positioned in thermal contact with a wafer positioned in a chamber of a reactor, and the contacting results in a roughening of the surface.