Front Metal Contact Stack for Photovoltaic Devices

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Solution Overview

Problem

Existing photovoltaic device manufacturing methods require high annealing temperatures for metal contacts, which can damage other components and are costly for large-scale production, and result in high contact resistivity.

Innovation Solution

A metal contact stack is formed using a first layer on a semiconductor layer, followed by a tin-based dopant layer and a conductive layer, with optional barrier layers, and annealed at a temperature below 200°C to achieve low contact resistivity without damaging the device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high annealing temperature is used to form metal contacts, then contact resistivity is reduced, but other device components are damaged

Engineering Contradiction:

Improvecontact resistivityVSAvoiddamage to device components

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The metal contact structure is segmented into multiple functional layers: a first metal layer in direct contact with the semiconductor, a second metal layer with intermediate annealing properties, and a third metal layer for current collection. This segmentation allows each layer to be optimized for specific functions, enabling low contact resistivity through the first layer while the other layers protect sensitive components from high temperature damage during annealing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second metal layer acts as an intermediary between the first metal layer and the third metal layer. It has intermediate annealing properties that allow it to facilitate dopant diffusion from the first layer while protecting the third layer and other device components from excessive temperature exposure, thus mediating between the need for low contact resistivity and component protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If high annealing temperature is used for metal contacts, then contact quality is improved, but manufacturing cost increases

Engineering Contradiction:

Improvecontact qualityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The multi-layer metal contact structure enables segmentation of the annealing process requirements. The first metal layer can be annealed at lower temperatures sufficient for dopant diffusion and low contact resistivity, while the other layers provide protection and current collection functions. This reduces the required annealing temperature, lowering manufacturing costs while maintaining contact quality.

Inventive Principle:

Principle #1Segmentation

3Reliability

If high annealing temperature is used for metal contacts, then current flow is improved, but energy consumption increases

Engineering Contradiction:

Improvecurrent flowVSAvoidannealing energy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The segmented metal contact structure with multiple layers having different annealing properties allows the annealing process to be optimized for minimal energy input. The first layer achieves sufficient dopant diffusion and low contact resistivity at lower temperatures, reducing the energy required for annealing while still enabling improved current flow through the contact structure.

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

The solution achieves low contact resistivity (less than 1 mΩ·cm2) at reduced annealing temperatures, preventing damage to other device components and reducing manufacturing costs, while using tin as a cost-effective alternative to germanium.

Implementation Method 1

depositing a dopant layer comprising tin (Sn) on the first layer... annealed at a temperature below 200°C to achieve low contact resistivity

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

depositing a first layer on a semiconductor layer... depositing a dopant layer comprising tin (Sn) on the first layer... depositing a conductive layer over the dopant layer

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS11257978B2Front metal contact stack

Publication Date: 2022.02.22 UTICA LEASECO LLC

AI summary

A photovoltaic device and a method of forming a contact stack of the photovoltaic device are disclosed. The photovoltaic device may include a first layer deposited on a semiconductor layer including a compound semiconductor material. The photovoltaic device may also include a dopant layer comprising tin (Sn) deposited on the first layer. The photovoltaic device may further include a conductive layer deposited or provided over the dopant layer to form a contact stack with the first layer and the dopant layer.