CIGS Solar Cell Back Contact Copper Molybdenum Adhesion
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Solution Overview
Problem
Traditional molybdenum back contacts in CIGS solar cells are costly, exhibit low conductivity, and suffer from delamination issues, while alternatives like tungsten and tantalum result in lower device efficiency.
Innovation Solution
A multi-layer back contact configuration using copper and molybdenum, with a copper oxide adhesion layer and optional MoCu alloy for thermal expansion matching, replacing a substantial portion of the molybdenum back contact to enhance conductivity and adhesion without compromising efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional molybdenum back contact is used in CIGS solar cells, then adhesion to the substrate is achieved, but production cost increases and conductivity decreases
Solution Approach 1:
The back contact is divided into multiple functional layers: a copper layer for cost reduction and conductivity enhancement, a copper oxide adhesion layer for substrate bonding, and a molybdenum layer for electrical contact with the CIGS absorber. This segmentation allows each layer to optimize its specific function while collectively solving the contradictions of cost, conductivity, and adhesion.
Solution Approach 2:
The invention uses a composite multi-layer structure combining copper, copper oxide, and molybdenum. This composite approach leverages the high conductivity and low cost of copper, the adhesion properties of copper oxide, and the electrical compatibility of molybdenum with CIGS, thereby resolving the technical contradictions simultaneously.
2Stability of the object's composition
If traditional molybdenum back contact is used in CIGS solar cells, then structural stability is achieved, but electrical conductivity decreases
Solution Approach 1:
The back contact structure is segmented into distinct layers with specialized functions: the copper layer provides high electrical conductivity and structural stability, the copper oxide layer ensures adhesion, and the molybdenum layer maintains electrical compatibility with the CIGS absorber. This segmentation allows optimization of both conductivity and structural stability.
Solution Approach 2:
The invention changes the material composition parameters of the back contact from pure molybdenum to a multi-layer copper-copper oxide-molybdenum structure. This parameter change increases electrical conductivity through the copper layer while maintaining structural stability through the combined layers, particularly the copper oxide adhesion layer that prevents delamination.
3Reliability
If alternative metals like tungsten or tantalum are used for back contact, then adhesion is improved, but device efficiency decreases
Solution Approach 1:
The invention applies local quality by using copper oxide specifically at the interface with the substrate where adhesion is needed, while using copper and molybdenum in regions where electrical conductivity and compatibility with the CIGS absorber are critical. This localized material selection achieves adhesion without compromising device efficiency.
Solution Approach 2:
The copper oxide layer acts as an intermediary between the copper/molybdenum back contact and the substrate. It provides the adhesion function that alternatives like tungsten or tantalum would offer, while the overall copper-copper oxide-molybdenum structure maintains the electrical properties needed for high device efficiency.
4Ease of manufacture
If copper is used as back contact material, then production cost decreases and conductivity improves, but adhesion to substrate deteriorates
Solution Approach 1:
The copper oxide layer serves as an intermediary between the copper layer and the substrate. It provides strong adhesion to the substrate while allowing the copper layer to maintain its low cost and high conductivity properties. This intermediary layer resolves the adhesion problem without sacrificing the benefits of copper.
Solution Approach 2:
The invention changes the oxidation state parameter of copper by introducing a copper oxide layer. This parameter change transforms copper from a material with poor adhesion to one that achieves strong substrate bonding, while the underlying copper layer continues to provide low cost and high conductivity.
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 configuration reduces production costs, improves conductivity, and maintains high efficiency by forming a thin, effective back contact that minimizes sheet resistance and mechanical stress, facilitating faster manufacturing and better adhesion.
Implementation Method 1
with a copper oxide adhesion layer
Implementation Method 2
The back (or rear) electrode may also function as a rear reflector in certain example instances
Data Source
AI summary
A photovoltaic device (e.g., solar cell) includes: a front substrate (e.g., glass substrate); a semiconductor absorber film; a back contact including a first conductive layer of or including copper (Cu) and a second conductive layer of or including molybdenum (Mo); and a rear substrate (e.g., glass substrate). The first conductive layer of or including copper is located between at least the rear substrate and the second conductive layer of or including molybdenum, and wherein the semiconductor absorber film is located between at least the back contact and the front substrate.