ZnTe Back Contact Electron Reflector for PV Efficiency
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Solution Overview
Problem
Photovoltaic devices face efficiency losses due to charge recombination and resistance at the interface between the absorber layer and the back current pathway, which are not effectively minimized by existing technologies.
Innovation Solution
Incorporating an electron reflector layer, such as zinc telluride (ZnTe) doped with copper telluride (Cu2Te) or a ZnTe/Cu2Te alloy, between the absorber layer and the back current pathway to reduce charge loss through electron reflection and provide a low-resistance ohmic contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a direct contact between the absorber layer and back current pathway is used, then the device structure is simple, but charge recombination and resistance losses occur at the interface
Solution Approach 1:
An electron reflector layer is introduced as an intermediary between the absorber layer and the back current pathway. This layer reflects electrons back into the absorber layer, preventing charge recombination at the interface, while also providing a low-resistance ohmic contact to the back current pathway, thus reducing resistance losses without significantly complicating the device structure.
Solution Approach 2:
The electron reflector layer is constructed using composite materials, specifically zinc telluride (ZnTe) doped with copper telluride (Cu2Te) or a ZnTe/Cu2Te alloy. This composite material structure provides both the electron reflection capability and the low-resistance ohmic contact properties, effectively addressing the energy loss issue while maintaining structural simplicity.
2Productivity
If existing back contact technologies are used, then the manufacturing process is straightforward, but efficiency losses are not minimized
Solution Approach 1:
The invention changes the material parameters of the back contact by using ZnTe doped with Cu2Te or ZnTe/Cu2Te alloy. This material parameter change enables the back contact to simultaneously provide electron reflection and low-resistance ohmic contact, thereby increasing electrical power generation efficiency. The manufacturing process remains straightforward as it follows conventional thin-film deposition techniques.
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 electron reflector layer significantly reduces charge recombination and resistance losses, enhancing the efficiency of photovoltaic devices by improving the flow of electrical current and increasing the maximum voltage production.
Implementation Method 1
Incorporating an electron reflector layer, such as zinc telluride (ZnTe) doped with copper telluride (Cu2Te) or a ZnTe/Cu2Te alloy, between the absorber layer and the back current pathway to reduce charge loss through electron reflection
Implementation Method 2
A photovoltaic device generates electrical power by converting light into direct current electricity using semiconductor materials that exhibit the photovoltaic effect. The photovoltaic effect generates electrical power upon exposure to light as photons, packets of energy, are absorbed within the semiconductor to excite electrons to a higher energy state.
Implementation Method 3
The semiconductor layer or layers will typically include a p-n junction that drives an electrical current as light is absorbed within the material. A p-n junction may be formed by of a bilayer where the first layer is an n-type layer referred to as the window layer and where the second layer is a p-type layer referred to as the absorber layer.
Data Source
AI summary
A photovoltaic device includes a substrate, a transparent conductive oxide, an n-type window layer, a p-type absorber layer and an electron reflector layer. The electron reflector layer may include zinc telluride doped with copper telluride, zinc telluride alloyed with copper telluride, or a bilayer of multiple layers containing zinc, copper, cadmium and tellurium in various compositions. A process for manufacturing a photovoltaic device includes forming a layer over a substrate by at least one of sputtering, evaporation deposition, CVD, chemical bath deposition process, and vapor transport deposition process. The process includes forming an electron reflector layer over a p-type absorber layer.