CdTe-Cu Photovoltaic Layer Fabrication Without CdS
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Solution Overview
Problem
The intermixed region at the cadmium telluride (CdTe)-cadmium sulfide (CdS) interface in photovoltaic devices negatively affects their performance, necessitating improved photovoltaic devices and methods that eliminate the need for a CdS layer.
Innovation Solution
A photovoltaic device comprising a support layer, a first n-type layer of cadmium, tellurium, and copper, and a second p-type layer of cadmium, tellurium, and copper, with a transparent conductive oxide layer, where the device is fabricated without a CdS layer through a method involving a stack of cadmium and tellurium layers and a copper layer, thermally annealed to form the n-type and p-type layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CdS layer is used at the interface with CdTe layer, then the device structure follows conventional design, but absorption losses occur and performance is negatively affected due to intermixed region formation
Solution Approach 1:
The patent removes the CdS layer from the device structure entirely, eliminating the source of absorption losses and intermixed region formation. The conventional CdTe-CdS interface is replaced with a direct CdTe contact to the back contact layer, extracting the problematic intermediate layer that caused performance degradation.
Solution Approach 2:
The patent converts the previously harmful CdS layer into a beneficial copper-containing layer that forms during thermal annealing. This layer, containing cadmium, tellurium, and copper with n-type and p-type regions, transforms the problematic interface into a functional component that enhances device performance while eliminating absorption losses.
2Ease of manufacture
If a CdS layer is included in the device structure, then conventional manufacturing processes can be used, but production costs increase and complexity is added
Solution Approach 1:
The patent merges the functions of multiple layers into a single copper-containing layer that forms during thermal annealing. Instead of maintaining separate CdS and CdTe layers with an interface, the process combines these into one integrated layer containing cadmium, tellurium, and copper that simultaneously provides the necessary electrical and optical functions.
Solution Approach 2:
The patent changes the chemical composition and structural parameters of the interface layer by introducing copper and allowing thermal annealing to create a copper-containing layer with specific n-type and p-type regions. This parameter change transforms the interface from a problematic multi-layer structure into a simplified single layer with optimized properties.
3Manufacturing precision
If thermal annealing is applied to the stack, then effective copper diffusion and layer formation occur, but energy consumption increases
Solution Approach 1:
The patent optimizes the thermal annealing parameters (temperature, time, atmosphere) to achieve effective copper diffusion and layer formation at reasonable energy costs. By carefully controlling these parameters, the process achieves precise compositional control in the copper-containing layer while minimizing excessive energy consumption.
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 enhances the efficiency of the photovoltaic device by eliminating absorption losses associated with the CdS layer and reduces production costs, while achieving effective electron-hole pair conversion from incident light.
Implementation Method 1
achieving effective electron-hole pair conversion from incident light
Implementation Method 2
eliminating absorption losses associated with the CdS layer
Data Source
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AI summary
A photovoltaic device includes a support layer; a first layer comprising cadmium, tellurium and copper and being of n-type; a second layer comprising cadmium, tellurium and copper and being of p-type; and a transparent conductive oxide layer. A method for making a photovoltaic device includes providing a stack comprising a cadmium and tellurium comprising layer and a copper comprising layer on the cadmium and tellurium comprising layer; and thermally annealing the stack to form a first layer and a second layer each comprising cadmium, tellurium and copper, the first layer being of n-type, the second layer being of p-type.