CdTe Solar Cell Layer Reduction Step

Solution Overview

Problem

The existing NP etching process for CdTe thin-film solar cells results in the formation of tellurium oxides, which degrade the conductivity and contacting quality due to oxidation, and previous methods using hazardous chemicals are either ineffective or impractical for industrial production.

Innovation Solution

An additional reduction step using aqueous solutions of sodium dithionite, stannous chloride, or sodium borohydride is introduced after NP etching to minimize tellurium oxide compounds in the Te-rich layer, ensuring the process is safe and industrially scalable.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If NP etching is used to create a Te-rich layer, then the layer structure is improved for ohmic contact, but tellurium oxides are formed that degrade conductivity and contacting quality

Engineering Contradiction:

Improvelayer structure qualityVSAvoidtellurium oxide formation

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The etching process is divided into two separate sequential steps: first NP etching to create the Te-rich layer, then a second etching step using a different chemical composition to remove tellurium oxides. This segmentation allows each step to perform its specific function optimally without interfering with the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A second etching solution acts as an intermediary between the NP etching step and the final metal contact deposition. This intermediary step specifically targets and removes tellurium oxides that would otherwise prevent good ohmic contact, bridging the gap between layer formation and contact quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If strong oxidizing acids are used for etching, then Te-rich layer formation is effective, but tellurium oxide compounds increase and degrade layer conductivity

Engineering Contradiction:

Improveetching efficiencyVSAvoidoxidation of tellurium

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The etching process is divided into two separate sequential steps: first NP etching to create the Te-rich layer, then a second etching step using a different chemical composition to remove tellurium oxides. This segmentation allows each step to perform its specific function optimally without interfering with the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The tellurium oxides formed during NP etching, which are initially harmful, are converted into removable byproducts in the second etching step. The oxidation that creates problems is subsequently reversed or removed, turning the harmful oxidation into a manageable intermediate state.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If wet chemical etching is applied to improve contacting, then the Te-rich layer is formed, but the process is time-consuming and complex

Engineering Contradiction:

Improvecontacting qualityVSAvoidetching process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The etching process is divided into two separate sequential steps: first NP etching to create the Te-rich layer, then a second etching step using a different chemical composition to remove tellurium oxides. This segmentation allows each step to perform its specific function optimally without interfering with the other.

Inventive Principle:

Principle #1Segmentation

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 effectively reduces tellurium oxides to a negligible amount, maintaining the Te-rich layer's thickness and conductivity, while avoiding the use of hazardous chemicals, thus improving the contacting quality and making the process suitable for industrial solar cell production.

Implementation Method 1

The invention provides that the NP etching, which is a well-managed process in the state of the art, is to be supplemented by an additional reduction step following the NP etching. This reductive treatment is aimed at eliminating most of the tellurium oxide compounds present in the Te-rich layer.

Methodology Applied

Scientific EffectReduction: Reduction

Data Source

PatentEP3051596B1Method for modifying cdte layer of cdte thin-layer solar cell

Publication Date: 2019.12.25 CHINA TRIUMPH INT ENG CO LTD

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Figure 5

AI summary

The subject matter of the present invention is a method for treating the CdTe layer of semifinished thin-film solar products in a superstrate configuration, having a CdTe layer as the uppermost layer. According to the state of the art, these surfaces are subjected to an NP etching and are then coated. However, the tellurium oxides formed during the NP etching have proven to be a disadvantage for the subsequent coating steps. It is therefore proposed that the tellurium oxides that are present should be reduced to tellurium using a reducing agent in a further treatment step.