Silicon Solar Cell Contact Grid Treatment With Local Ohmic Feedback
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Solution Overview
Problem
Existing methods for improving ohmic-contact behavior between a contact grid and an emitter layer of a silicon solar cell are time-consuming and can cause damage due to unknown local variations and require post-processing characterization, making it difficult to quantify improvements and detect damage.
Innovation Solution
A method involving a treatment step with a voltage source and a point light source to induce a current flow, accompanied by spatially resolved measurement steps to sense and store current flows, allowing for process control and damage detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a point light source is guided over the solar cell to induce treatment current flow, then the ohmic-contact behavior is improved, but the processing time increases due to the need for spatially resolved treatment and measurement
Solution Approach 1:
The solar cell surface is divided into multiple measurement sections that are treated and measured individually. The point light source is guided sequentially over different sub-areas, inducing treatment current flow in each section. This segmentation allows for spatially resolved processing while maintaining overall efficiency by treating only necessary regions.
Solution Approach 2:
Measurement steps are performed before the treatment step to identify regions requiring improvement. By pre-characterizing the solar cell and locating areas with insufficient ohmic-contact behavior, the treatment can be targeted precisely to those regions, avoiding unnecessary processing of already adequate areas and thus reducing total processing time.
2Ease of manufacture
If uniform treatment parameters are applied across the entire solar cell, then the process is simple, but local variations in ohmic-contact behavior cannot be addressed
Solution Approach 1:
Different treatment parameters (illumination intensity, exposure time, current density) are applied to different measurement sections based on their specific needs. The system adapts the treatment to local conditions by adjusting parameters according to the measured characteristics of each sub-area, ensuring optimal ohmic-contact behavior in each region rather than applying a one-size-fits-all approach.
Solution Approach 2:
The treatment parameters are made dynamic and adaptive rather than static and uniform. The system continuously adjusts illumination intensity and exposure time based on real-time measurement feedback from each measurement section. This dynamic adaptation allows the process to respond to local variations in solar cell characteristics, achieving high manufacturing precision while maintaining reasonable process complexity.
3Reliability
If high current density is applied to improve contact behavior, then the ohmic-contact is enhanced, but the risk of damaging the solar cell increases
Solution Approach 1:
Measurement steps are performed both before and after the treatment step to monitor changes in current flow through measurement sections. This feedback mechanism allows the system to detect improvements in ohmic-contact behavior and stop treatment when target values are achieved, preventing over-treatment and potential damage. The treatment current density and exposure time are adjusted based on feedback from measurement results.
Solution Approach 2:
The treatment is applied with sufficient current density to achieve the desired ohmic-contact improvement, but only for the minimum necessary duration and only in regions where improvement is needed. By using measurement feedback to determine when target values are reached, the system avoids excessive treatment that could damage the cell, applying just enough action to achieve the required contact quality.
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
Enables spatially resolved quantification of ohmic-contact behavior improvement and detection of damage, optimizing the process and reducing the risk of cell damage.
Implementation Method 1
a point light source is guided over the sun-facing side of the silicon solar cell, whereby treatment sections of sub-areas of the sun-facing side are illuminated and thus a treatment current flow is induced in the respective sub-area
Data Source
AI summary
The invention relates to a method for improving the ohmic-contact behaviour between a contact grid and an emitter layer of a silicon solar cell, in which, in a treatment step, a treatment current flow having a current density of 200 A/cm2 to 20,000 A/cm2 in relation to the treatment section is induced while biasing and illuminating the silicon solar cell. The object of the invention is to improve the method for improving the ohmic-contact behaviour between a contact grid and an emitter layer of a silicon solar cell. In particular, it should be possible to quantify the improvement achieved by the method while implementing the method. Furthermore, any damage resulting from the application of unfavourable process parameters should be detected while the method is being implemented. This object is achieved in that a measurement step is carried out before and/or after the treatment step, and, in said measurement step, a measurement current flow having a current density of 1 mA/cm2 to 500 mA/cm2 is induced by illuminating the sun-facing side of the silicon solar cells and biasing, and a current strength of said measurement current flow is sensed using an ammeter and stored assigned to the respective measurement section.