Thin-Film Solar Absorber Activation Without CdCl2 Residues

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The use of CdCl2 in activating absorber layers of CdTe or CdSeTe thin-film solar cells poses environmental and health hazards due to its toxicity and carcinogenic properties, necessitating a safer alternative for effective activation and waste management.

Innovation Solution

A method involving the use of a polyvinylchloride (PVC) film, which decomposes during heat treatment to release hydrogen chloride, facilitating the activation of the absorber layer without the need for CdCl2, thereby reducing toxicity and environmental impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If CdCl2 is used to activate the absorber layer, then good electrical characteristics and recrystallization are achieved, but environmental hazards and health risks increase due to toxicity

Engineering Contradiction:

Improveelectrical characteristicsVSAvoidtoxicity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A polyvinylchloride (PVC) layer is introduced as an intermediary substance that decomposes during heat treatment to release HCl in situ. This mediator enables the activation process without requiring direct handling of toxic CdCl2, as the PVC layer serves as a precursor that converts to the needed HCl under processing conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The PVC layer is applied as a disposable sacrificial material that is completely consumed during the heat treatment process. It serves its purpose by decomposing to provide HCl for activation, then is removed as waste, eliminating the need for subsequent rinsing steps required when using CdCl2

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Stability of the object's composition

If CdCl2 is used for activation, then absorber layer recrystallization is achieved, but hazardous waste generation increases

Engineering Contradiction:

ImproverecrystallizationVSAvoidhazardous waste

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The harmful decomposition products of PVC (HCl and other gases) are converted into a beneficial activation mechanism. The HCl released during PVC decomposition performs the necessary chemical activation and recrystallization of the absorber layer, transforming what would be harmful emissions into a useful processing function

Inventive Principle:

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

Solution Approach 2:

PVC acts as a intermediary that delivers the necessary HCl for recrystallization without introducing persistent hazardous residues. The decomposition products either serve the activation function or can be more easily managed compared to CdCl2 waste streams

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If CdCl2 is applied and then rinsed off, then activation is achieved, but additional processing steps and water consumption are required

Engineering Contradiction:

ImproveactivationVSAvoidprocessing steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The PVC layer is designed as a consumable material that fulfills its activation function and then disappears during heat treatment. This eliminates the need for subsequent rinsing operations to remove residual CdCl2, simplifying the process flow and reducing water consumption

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The activation function is performed in advance during the heat treatment step itself, rather than requiring a separate post-treatment rinsing step. The PVC decomposition and HCl release occur simultaneously with the activation process, integrating multiple functions into a single operation

Inventive Principle:

Principle #10Preliminary action

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 replaces CdCl2 with a less hazardous substance, ensuring safer handling and waste management while maintaining the electrical properties of the solar cells, with improved recrystallization processes at temperatures between 300° C. and 500° C., and allows for the formation of CdSexTe1-x layers with enhanced alloying states and mixing ratios.

Implementation Method 1

the polyvinylchloride film decomposes and the released hydrogen chloride (H+Cl−) may enter the absorber layer via the surface and/or the grain boundaries and initiate the activation process

Methodology Applied

Scientific EffectThermal decomposition: Pyrolysis

Implementation Method 2

the CdCl2 acts as fluxing agent and supports a recrystallisation of the CdTe or CdSexTe1-x layer

Methodology Applied

Scientific EffectRecrystallization: Crystallisation

Data Source

PatentUS20250015219A1Method for activating an absorber layer of a thin-film solar cell

Publication Date: 2025.01.09 CHINA TRIUMPH INT ENG CO LTD

AI summary

The invention refers to a method for activating an absorber layer of a semi-finished thin-film solar cell. The absorber layer comprises CdSexTe1-x, CdSe, CdS or CdTe. The method comprises the steps of providing a semi-finished thin-film solar cell with an absorber layer comprising a CdSexTe1-x, layer or comprising at least two layers selected from CdS, CdTe, ZnTe, CdSe, forming a polyvinylchloride film on a surface of the absorber layer, and performing a heat treatment of the semi-finished thin-film solar cell with the polyvinylchloride film on it, wherein the temperature is in the range of 300° C. to 500° C.