CdTe Photovoltaic Device Copper-Free Doping Stability
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Solution Overview
Problem
Cadmium telluride (CdTe)-based photovoltaic devices face low power conversion efficiencies due to low open circuit voltage, low effective carrier concentration, and high back-contact resistance, which are exacerbated by the instability and mobility of copper when used in doping and ohmic contact formation.
Innovation Solution
A method involving the use of manganese, cobalt, nickel, or zinc metal salts to form doped absorber layers and interfacial layers, free from copper, to enhance carrier concentration and reduce back-contact resistance, thereby improving the efficiency and stability of photovoltaic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used for doping the absorber layer and forming ohmic contact, then carrier concentration increases and back-contact resistance decreases, but long-term stability deteriorates due to copper mobility and instability
Solution Approach 1:
The patent changes the material parameter from copper-based dopant to non-copper metal dopants (Group IIB metals: Zn, Cd, Hg; Group IVB metals: Pb; or Group VB metals: Bi). This parameter substitution eliminates the harmful mobility and instability of copper while maintaining the beneficial electrical properties of doped absorber layers, thereby improving long-term stability without sacrificing carrier concentration enhancement.
2Productivity
If copper-based doping is employed to increase carrier concentration, then power conversion efficiency improves, but device stability deteriorates
Solution Approach 1:
The invention substitutes copper dopants with alternative metals (Group IIB, IVB, or VB) that provide similar or enhanced carrier concentration improvement while eliminating the stability issues associated with copper. This parameter change enables simultaneous achievement of high power conversion efficiency and device stability.
Solution Approach 2:
The patent replaces the unstable copper-based doping approach with stable non-copper metal dopants that provide lasting, reliable performance. The alternative dopants create stable ohmic contacts and maintain consistent electrical properties over time, effectively replacing the short-lived stability of copper-based systems.
3Productivity
If open circuit voltage is increased through doping, then power conversion efficiency improves, but manufacturing complexity increases due to additional processing steps
Solution Approach 1:
The patent combines the doping function and ohmic contact formation function into a single integrated process step. By applying a solution containing non-copper metal salts that perform both doping of the absorber layer and formation of stable ohmic contacts simultaneously, the method reduces manufacturing complexity while achieving the dual benefit of increased open circuit voltage and improved device stability.
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 method increases the open circuit voltage and fill factor, leading to higher photovoltaic device efficiency and stability, with improved carrier concentration and reduced resistivity, outperforming copper-based approaches.
Implementation Method 1
treating at least a portion of the absorber layer with a first solution including a first metal salt to form a first component
Implementation Method 2
treating at least a portion of the first component with cadmium chloride to form a second component
Implementation Method 3
treating at least a portion of the second component with a second solution including a second metal salt to form an interfacial layer on the second component
Implementation Method 4
The window layer allows the penetration of solar radiation to the absorber layer, where the optical energy is converted to usable electrical energy
Data Source
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AI summary
One aspect of the present invention includes a method of making a photovoltaic device. The method includes disposing an absorber layer (130) on a window layer (120). The method further includes treating at least a portion of the absorber layer with a first solution including a first metal salt to form a first component (142), wherein the first metal salt comprises a first metal selected from the group consisting of manganese, cobalt, chromium, zinc, indium, tungsten, molybdenum, and combinations thereof. The method further includes treating at least a portion of the first component with cadmium chloride to form a second component (150). The method further includes treating at least a portion of the second component with a second solution including a second metal salt to form an interfacial layer on the second component (160), wherein the second metal salt comprises a second metal selected from the group consisting of manganese, cobalt, nickel, zinc, and combinations thereof.