Graded CdS-CdTe Intermixing for PV Junction Control

Solution Overview

Problem

The challenge in manufacturing cadmium telluride photovoltaic devices lies in achieving uniform and controlled intermixed layers of cadmium sulfide and cadmium telluride, which is crucial for improving the p-n junction efficiency but is affected by various manufacturing variables, leading to inconsistent device performance during large-scale production.

Innovation Solution

A process is developed to form an intermixed layer of cadmium sulfide and cadmium telluride by introducing a sulfur-containing gas during the deposition of the cadmium telluride layer, creating a graded layer with increasing tellurium concentration and decreasing sulfur concentration, which is controlled through the thickness to tailor the interaction between the window layer and the cadmium telluride layer, using a vapor deposition apparatus with a distribution plate and gas supply system to ensure uniform deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If annealing process is used to create intermixed layers, then minority carrier lifetime and open circuit voltage are improved, but manufacturing uniformity and device consistency deteriorate due to sensitivity to process variables

Engineering Contradiction:

Improveminority carrier lifetimeVSAvoiduniformity of intermixed layer

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The intermixed layer is formed during the deposition process itself, before the annealing step. By pre-forming the intermixed layer with controlled composition gradients during deposition, the need for extensive post-deposition annealing is reduced, thereby achieving improved minority carrier lifetime while maintaining better manufacturing uniformity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the deposition parameters to control the composition of the intermixed layer directly during deposition. By adjusting source material ratios, deposition temperature, and gas flow rates, the intermixed layer composition can be precisely controlled without relying on post-deposition annealing variables, thus improving both reliability and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If annealing temperature and time are increased to enhance intermixing, then p-n junction efficiency is improved, but device uniformity and scalability worsen

Engineering Contradiction:

Improvep-n junction efficiencyVSAvoidscalability to large scale manufacturing

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The intermixed layer is formed during the deposition process itself, before the annealing step. By pre-forming the intermixed layer with controlled composition gradients during deposition, the need for extensive post-deposition annealing is reduced, thereby achieving improved minority carrier lifetime while maintaining better manufacturing uniformity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the deposition parameters to control the composition of the intermixed layer directly during deposition. By adjusting source material ratios, deposition temperature, and gas flow rates, the intermixed layer composition can be precisely controlled without relying on post-deposition annealing variables, thus improving both reliability and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

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 allows for better control of the stoichiometry and uniformity of the p-n junction, enhancing the open circuit voltage and fill factor of the photovoltaic devices, thereby improving their efficiency and consistency across multiple devices.

Implementation Method 1

A source vapor can be supplied to the deposition chamber, wherein the source material comprises cadmium telluride. The sulfur-containing gas and the source vapor can be present within the deposition chamber to form an intermixed layer on the window layer.

Methodology Applied

Scientific EffectVapor deposition: Physical Vapour Deposition

Data Source

PatentUS8349084B2Apparatus and systems for intermixing cadmium sulfide layers and cadmium telluride layers for thin film photovoltaic devices

Publication Date: 2013.01.08 FIRST SOLAR INC

AI summary

An apparatus for sequential deposition of an intermixed thin film layer and a sublimated source material on a photovoltaic (PV) module substrate is provided, along with associated processes. The process can include introducing a substrate into a deposition chamber, wherein a window layer (e.g., a cadmium sulfide layer) is on a surface of the substrate. A sulfur-containing gas can be supplied to the deposition chamber. In addition, a source vapor can be supplied to the deposition chamber, wherein the source material comprises cadmium telluride. The sulfur-containing gas and the source vapor can be present within the deposition chamber to form an intermixed layer on the window layer. In one particular embodiment, for example, the intermixed layer generally can have an increasing tellurium concentration and decreasing sulfur concentration extending away from the window layer.