CIGS Absorber Surface Modification via Alkaline Metal Annealing

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Solution Overview

Problem

Inclusion of alkaline metals in CIGS absorber formation can alter the thermal properties of the substrate, affecting the performance of thin-film photovoltaic devices, and existing methods do not effectively manage the copper concentration at the surface of the absorber layer.

Innovation Solution

Depositing an alkaline metal layer on the CIGS absorber and annealing it with a suitable gas to drive a reaction, resulting in a copper-poor surface region, which enhances the electrical performance by reducing copper concentration at the interface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If alkaline metals are included in CIGS absorber formation, then the electrical performance is improved, but the thermal properties of the substrate are altered

Engineering Contradiction:

Improveelectrical performanceVSAvoidthermal properties

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The absorber layer is divided into two distinct regions: a bulk region containing alkaline metals for improved electrical performance, and a surface region depleted of alkaline metals and copper for stable thermal properties. This spatial segmentation allows each region to optimize its function independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different compositional qualities are applied to different locations within the absorber layer. The bulk maintains high alkaline metal concentration for electrical performance, while the surface (within 50nm of the interface) has reduced alkaline metal and copper concentrations for thermal stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If copper concentration is high in the absorber layer, then the electrical conductivity is improved, but the surface copper excess causes performance degradation at the interface

Engineering Contradiction:

Improveelectrical conductivityVSAvoidsurface copper excess

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Excess copper is selectively removed from the surface region of the absorber layer through the alkaline metal deposition and annealing process. The copper is extracted from the interface region and redistributed, creating a copper-poor surface layer that eliminates interface degradation while preserving bulk conductivity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The deposited alkaline metal layer serves as an intermediary that facilitates copper redistribution. During annealing, the alkaline metals interact with copper at the surface, enabling copper to be moved from the interface region into the bulk or removed, thereby mediating the copper concentration profile optimization.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If the absorber surface is copper-rich, then the light absorption is enhanced, but the interface with the buffer layer suffers from poor electrical contact

Engineering Contradiction:

Improvelight absorptionVSAvoidelectrical contact

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The absorber layer is given non-uniform compositional quality: the bulk remains copper-rich for light absorption, while the surface region (within 50nm of the interface) becomes copper-poor through annealing with deposited alkaline metals, creating optimal electrical contact with the buffer layer.

Inventive Principle:

Principle #3Local 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

This approach increases the efficiency of the CIGS absorber by creating a copper-poor surface region, improving the electrical performance and thermal stability of the solar cell.

Implementation Method 1

annealing it with a suitable gas to drive a reaction, resulting in a copper-poor surface region

Methodology Applied

Scientific EffectAnnealing: Annealing

Implementation Method 2

drive a reaction between the alkaline metal layer and the absorber, resulting in a copper-poor surface region of the absorber at the interface

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS10516069B2Absorber surface modification

Publication Date: 2019.12.24 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides systems and methods for depositing an alkaline metal layer on an absorber to generate a copper-poor region at a surface of the absorber. The copper-poor region provides an increased efficiency over non-treated absorbers having copper-rich surfaces. The alkaline metal layer may be deposited by any suitable deposition method, such as, for example, a wet deposition method. After the alkaline metal layer is deposited, the absorber is annealed, causing the alkaline metal layer to interact with the absorber to reduce the copper-profile of the absorber at the interface between the alkaline metal layer and the absorber.