Copper Diffusion Doping in Cadmium Telluride Photovoltaic Absorbers

Solution Overview

Problem

The existing methods for doping cadmium telluride layers in thin film photovoltaic devices require significant processing steps and often use toxic chemicals like copper chloride, which is undesirable.

Innovation Solution

Doping is achieved by diffusing copper from a window layer into the cadmium telluride absorber layer through annealing, eliminating the need for additional copper treatment and reducing processing complexity while avoiding toxic chemicals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If copper doping is achieved by treating the cadmium telluride layer with copper chloride and heating, then the dopant is effectively introduced into the absorber layer, but significant processing requirements and use of toxic chemicals are added

Engineering Contradiction:

Improvedoping effectivenessVSAvoidprocessing requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The copper dopant is pre-loaded into the window layer during its deposition process, before the absorber layer is formed. This preliminary incorporation of the dopant into the window layer eliminates the need for subsequent copper chloride treatment steps, as the dopant is already in position to diffuse into the absorber layer during the standard annealing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The toxic copper chloride treatment step is extracted and removed from the manufacturing process. Instead of using copper chloride to introduce copper into the absorber layer, the copper is obtained from the window layer through diffusion, eliminating the harmful chemical treatment while maintaining doping effectiveness.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If copper doping is achieved by treating the cadmium telluride layer with copper chloride and heating, then the dopant is effectively introduced into the absorber layer, but toxic chemicals like copper chloride must be used

Engineering Contradiction:

Improvedoping effectivenessVSAvoidtoxic chemical treatment

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The toxic copper chloride treatment step is extracted and removed from the manufacturing process. Instead of using copper chloride to introduce copper into the absorber layer, the copper is obtained from the window layer through diffusion, eliminating the harmful chemical treatment while maintaining doping effectiveness.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The window layer, which would normally just serve as a transparent contact layer, is converted into a dopant source. By loading copper into the window layer during deposition, it serves a dual function: maintaining electrical contact and providing the dopant needed for absorber layer doping, thereby eliminating the need for toxic chemicals.

Inventive Principle:

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

3Manufacturing precision

If a separate copper treatment step is added to dope the absorber layer, then the dopant concentration can be controlled, but the manufacturing process complexity increases

Engineering Contradiction:

Improvedopant concentration controlVSAvoidprocessing steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The copper dopant is pre-loaded into the window layer during its deposition process, before the absorber layer is formed. This preliminary incorporation of the dopant into the window layer eliminates the need for subsequent copper chloride treatment steps, as the dopant is already in position to diffuse into the absorber layer during the standard annealing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The window layer is given multiple functions: it serves as the transparent electrical contact layer and simultaneously as the dopant source for the absorber layer. This multi-functionality eliminates the need for separate doping treatment steps, reducing process complexity while maintaining dopant concentration control through the initial loading amount.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 method effectively introduces the required dopant into the cadmium telluride layer, enhancing the photovoltaic device's performance without the need for toxic treatments and simplifying the manufacturing process.

Implementation Method 1

The dopant can then be diffused from the window layer into the absorber layer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

Diffusing the dopant from the window layer into the absorber layer can be achieved, in one embodiment, via annealing the absorber layer and the window layer together

Methodology Applied

Scientific EffectAnnealing: Annealing

Data Source

PatentUS9564543B2Doping an absorber layer of a photovoltaic device via diffusion from a window layer

Publication Date: 2017.02.07 FIRST SOLAR INC

AI summary

Methods for doping an absorbent layer of a p-n heterojunction in a thin film photovoltaic device are provided. The method can include depositing a window layer on a transparent substrate, where the window layer includes at least one dopant (e.g., copper). A p-n heterojunction can be formed on the window layer, with the p-n heterojunction including a photovoltaic material (e.g., cadmium telluride) in an absorber layer. The dopant can then be diffused from the window layer into the absorber layer (e.g., via annealing).