Selectively Patterned Transparent Conductive Coatings for PV Cells
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Solution Overview
Problem
Concentrating photovoltaic systems face significant resistive power losses and optical obscuration due to closely spaced, optically opaque gridlines, which limit efficiency at high concentrations, and existing transparent conductive coatings do not adequately address these issues in high-efficiency multijunction cells.
Innovation Solution
A selectively patterned, transparent conductive coating is applied contiguous with the gridlines on the sunward surface of semiconductor wafers in concentrating photovoltaic systems, allowing for increased gridline spacing and reduced resistive power losses while maintaining optical transmission, thereby optimizing the balance between conductivity and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If closely spaced metal gridlines are used to reduce resistive power loss, then electrical conductivity is improved, but optical transmission is worsened due to obscuration
Solution Approach 1:
A transparent conductive coating is introduced as an intermediary material between the metal gridlines and the semiconductor. This TCC layer has high optical transparency allowing light to pass through while providing additional electrical conduction path, thus reducing resistive losses without compromising optical transmission. The TCC acts as a mediator that combines the benefits of both conductivity and transparency.
Solution Approach 2:
The patent employs a composite structure combining metal gridlines with transparent conductive coating materials. This composite approach allows the system to leverage the high conductivity of metals while the transparent coating provides optical transparency and additional conduction pathways, achieving a balance between electrical performance and optical transmission that neither material could achieve alone.
2Loss of energy
If blanket transparent conductive coating is applied to reduce resistive losses, then electrical conductivity is improved, but optical transmission is worsened due to partial opacity
Solution Approach 1:
The transparent conductive coating is segmented into discrete regions rather than applied as a continuous blanket coating. The coating is applied only in specific areas such as along the gridline regions where current density is highest, leaving other areas of the semiconductor surface uncovered. This segmentation allows the TCC to provide electrical conduction where needed while minimizing optical transmission losses by reducing the total coated area.
Solution Approach 2:
The transparent conductive coating is applied with non-uniform distribution, concentrating the coating material in regions of high current density near the gridlines while leaving regions of low current density uncovered. This local quality approach ensures that the TCC provides electrical conduction precisely where it is most needed for reducing resistive losses, while maintaining high optical transmission in areas where current flow is minimal.
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 results in a net increase in absolute cell efficiency, with experimental results showing a greater than 0.5% efficiency increase at 1000x concentration, comparable to a year's worth of typical multijunction solar cell development progress.
Implementation Method 1
The solar cell comprises semiconductors that convert sunlight into electricity
Implementation Method 2
TCCs provide electrical conduction (reduced resistance) while allowing light to pass through them
Data Source
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AI summary
A photovoltaic cell comprising a selectively patterned, transparent, conductive coating (TCC) on a sunward surface. The selectively patterned TCC is contiguous with at least some highly conductive gridlines on the sunward surface. A portion of the sunward surface of the semiconductor wafer is not covered by either the gridlines or the TCC. Also disclosed are methods of manufacturing a photovoltaic cell comprising a selectively patterned, transparent, conductive coating (TCC) on a sunward surface. The methods include the step of modeling the optical and electrical properties of the semiconductor, the gridlines, and the TCC to determine a pattern for the TCC that results in a low relative power loss for the photovoltaic cell.