ZnTe Contact Interface Layer for CdTe PV Back Contacts
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Solution Overview
Problem
CdS/CdTe photovoltaic devices face challenges with insufficient electrical quality of the as-deposited CdTe layer, which affects device functionality due to low net acceptor density and n-type material issues, and Cu diffusion is crucial but can be hindered by oxidation, impacting reproducibility and efficiency.
Innovation Solution
The use of a sputter-deposition target with a contact interface material, a p-type dopant, and a gettering metal like Ti, deposited in an inert atmosphere to form a ZnTe:Cu contact interface layer, with TiTe2 as a non-oxide compound to prevent oxidation and enhance Cu diffusion, resulting in a more reproducible and efficient back contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Cu diffusion is used to improve electrical properties of CdTe layer, then device efficiency is improved, but oxidation of Cu can hinder diffusion and reduce reproducibility
Solution Approach 1:
A ZnTe contact interface layer is introduced as an intermediary between the Cu-containing back contact and the CdTe absorber layer. This interface layer facilitates controlled Cu diffusion into the CdTe while protecting the Cu from oxidation, thereby improving device efficiency and reproducibility
Solution Approach 2:
The deposition and processing are conducted in an inert atmosphere (such as nitrogen or argon) to prevent oxidation of Cu. This creates a protective environment that maintains Cu in its metallic state, enabling effective diffusion while avoiding harmful oxidation effects
2Ease of manufacture
If as-deposited CdTe layer is used, then deposition process is simple, but electrical quality is insufficient for effective junction operation
Solution Approach 1:
The ZnTe contact interface layer is deposited preliminarily before the CdTe absorber layer. This pre-deposited layer is designed to facilitate subsequent Cu diffusion and improve the electrical quality of the CdTe layer, enabling effective junction operation without complicating the overall deposition process
Solution Approach 2:
The electrical properties of the CdTe layer are improved by changing parameters through Cu diffusion facilitated by the ZnTe interface layer. This process adjusts the carrier concentration and electrical quality of the CdTe layer to achieve values suitable for effective junction operation
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 approach improves the electrical properties of the CdTe layer by ensuring Cu diffusion and reducing oxygen-induced oxidation, leading to higher device voltages and enhanced efficiency in CdS/CdTe PV devices.
Implementation Method 1
Some disclosed embodiments are methods of forming a back contact in a CdS/CdTe PV device. The methods include providing a sputter-deposition target made of at least a contact interface material, a p-type dopant and a gettering metal, depositing a contact interface layer from the target to a CdTe device layer
Implementation Method 2
Cu must diffuse from the contact interface layer into the CdTe layer to improve CdS/CdTe device functionality by causing the CdTe layer to become p-type
Implementation Method 3
For example, oxidation of Cu to form CuO during or after deposition of the contact interface layer can limit diffusion of any Cu contained within an oxide
Data Source
AI summary
Disclosed embodiments include CdS/CdTe PV devices (100) having a back contact (110,112) with oxygen gettering capacity. Also disclosed are back contact structures (110, 112) and methods of forming a back contact in a CdS/CdTe PV device (100). The described contacts and methods feature a contact having a contact interface layer (100) comprising a contact interface material, a p-type dopant and a gettering metal.