CdSeTe Photovoltaic Junction Structure for Window Layer Stability
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Solution Overview
Problem
Photovoltaic devices face efficiency losses due to the scattering of charge carriers at grain boundaries between crystalline materials, which can be exacerbated by aggressive activation processes that degrade the thin window layer, making it difficult to maintain a robust p-n junction while optimizing the absorber layer.
Innovation Solution
Incorporating a cadmium sulphoselenide (CdSSe) layer as the n-type window layer and using a cadmium telluride (CdTe) absorber layer, with an interfacial layer or additional layers like cadmium sulphotelluride (CST) to form a p-n junction, and employing a chlorine-based activation process to enhance the absorber layer without degrading the window layer, allowing for more aggressive activation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thin window layer is used to allow maximum light transmission, then light absorption efficiency is improved, but the window layer becomes vulnerable to degradation during activation processes
Solution Approach 1:
The patent employs a composite window layer structure consisting of CdS and CdSSe materials. The CdSSe component serves as a protective layer that is more resistant to degradation during activation processes, while the CdS component maintains optimal optical properties for light transmission. This composite approach allows the window layer to be sufficiently thin for high light transmission while the CdSSe portion provides enhanced structural integrity and resistance to activation-induced damage.
2Productivity
If aggressive activation processes are applied to improve absorber layer performance, then charge carrier generation is enhanced, but the window layer suffers degradation
Solution Approach 1:
The CdSSe layer acts as an intermediary protective barrier between the activation process and the CdS window layer. During aggressive activation treatments, the CdSSe layer absorbs much of the chemical and thermal stress, preventing direct interaction with the more sensitive CdS window layer. This mediator layer enables the application of potent activation conditions that enhance charge carrier generation in the absorber layer while preserving window layer integrity.
3Reliability
If the window layer is made thicker to maintain robust p-n junction, then junction stability is improved, but light transmission efficiency decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform window layer structure where different regions have different compositions and thicknesses. The CdSSe portion is strategically positioned to provide localized protection and structural support, while other regions maintain optimal thickness for light transmission. This spatial variation in material properties allows the window layer to simultaneously achieve sufficient robustness for stable p-n junction formation and adequate thinness for high light transmission efficiency.
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 improves the efficiency of the p-n junction by reducing recombination of charge carriers and maintaining the integrity of the thin window layer, enabling higher voltage production and reduced resistivity, thus enhancing the overall energy conversion efficiency of the photovoltaic device.
Implementation Method 1
A photovoltaic structure generates electrical power by converting light into direct current electricity using semiconductor materials that exhibit the photovoltaic effect
Implementation Method 2
photons, packets of energy, are absorbed within the semiconductor to excite electrons to a higher energy state
Data Source
AI summary
A photovoltaic device includes a substrate structure and a p-type semiconductor absorber layer. A photovoltaic device may include a CdSeTe layer. A process for manufacturing a photovoltaic device includes forming a CdSeTe layer over a substrate. The process includes forming a p-type cadmium selenide telluride absorber layer.