Textured TCO Layer Stacks for Reduced Light Reflection
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Solution Overview
Problem
Existing photovoltaic devices suffer from energy loss due to light reflection at the glass substrate and layer interfaces within the transparent conductive oxide (TCO) stack, necessitating improved TCO layer stacks and deposition methods to minimize this loss.
Innovation Solution
The method involves sputtering a TCO material on a glass substrate with controlled sputtering conditions to create a textured topography at the interfaces, reducing reflection by minimizing the difference in refractive indices through hybrid interfacial transition regions formed by intermingling semiconductor materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional TCO layer stacks are used with smooth interfaces, then the device structure is simple and easy to manufacture, but light reflection is high and energy loss occurs
Solution Approach 1:
The patent applies local quality by creating textured surfaces only at specific interfaces within the TCO layer stack where light reflection occurs, while maintaining smooth surfaces in other regions. The texturing is localized to the front interface and intermediate interfaces to reduce reflection without affecting the entire structure uniformly.
Solution Approach 2:
The patent introduces textural features that extend into the third dimension (surface protrusions and recesses) to reduce light reflection. By creating a textured topography with vertical features, the patent transforms a two-dimensional smooth interface into a three-dimensional structured surface that scatters light and reduces reflection.
2Illumination intensity
If textured topography is introduced at TCO interfaces, then light reflection is reduced and light transmission is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent controls the textural parameters (protrusion height, recess depth, surface area) within specific ranges to achieve optimal light transmission while maintaining manufacturability. By defining quantitative parameters for the texture features, the patent enables precise control during the sputtering deposition process.
Solution Approach 2:
The textured interfaces act as intermediary structures between the glass substrate and TCO layers, or between TCO layers, mediating the light transmission process. These intermediate textural features create multiple reflection paths and reduce direct reflection, enhancing overall light transmission to the absorber layer.
3Productivity
If sputtering conditions are optimized to create textured topography, then internal reflection is reduced and electrical current density increases, but deposition time and process complexity increase
Solution Approach 1:
The texturing process is integrated into the continuous sputtering deposition process, where the textured surface forms automatically during the deposition of subsequent TCO layers. This eliminates the need for separate texturing steps and maintains continuous productive action throughout the manufacturing process.
Solution Approach 2:
The textured surface is formed during the deposition of lower TCO layers before the final absorber layer is deposited. This preliminary texturing prepares the interface in advance to reduce reflection when light reaches it during device operation, without requiring additional post-processing time.
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 light transmission and increases electrical current density by reducing internal reflection, thereby improving the efficiency of photovoltaic devices.
Implementation Method 1
sputtering a transparent conductive oxide (TCO) material, such as a TCO material deposited on a glass substrate
Implementation Method 2
reducing reflection by minimizing the difference in refractive indices through hybrid interfacial transition regions formed by intermingling semiconductor materials
Implementation Method 3
reducing reflection by minimizing the difference in refractive indices
Implementation Method 4
A photovoltaic device generates electrical power by converting light into electricity using semiconductor materials that exhibit the photovoltaic effect to generate current
Data Source
AI summary
According to the embodiments provided herein, a method for sputtering a TCO material onto a substrate includes process conditions that produce a textured topography at the interfaces of various layers. The textured topography can include an average roughness from about 5 to about 40 nm. The process conditions can include providing oxygen in the sputtering environment at a flow rate of from 0 to about 30 sccm; or heating the substrate to at least 200; or increasing the magnetic field strength to above 40 mT. The textured topography creates interfacial transition areas which have hybrid physical properties compared to their constituent materials.