CIGS Absorber Layer Passivation Without Air Break Interface Traps
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Solution Overview
Problem
Current methods for manufacturing CIGS-based photovoltaic devices expose the CIGS layer to air and moisture during transfer, leading to interface traps that reduce quantum efficiency and charge collection.
Innovation Solution
The method involves performing physical vapor deposition of the CIGS absorber layer in vacuum without an air break, followed by in-situ oxygen annealing to passivate selenium vacancies, and then depositing a cap layer in vacuum to further minimize interface traps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the CIGS layer is transferred from one processing chamber to the next using an air break, then the manufacturing process can be completed, but interface traps are created on the CIGS surface due to exposure to air and moisture
Solution Approach 1:
The patent applies inert atmosphere by performing in-situ oxygen annealing of the CIGS absorber layer within the vacuum environment of the deposition chamber, avoiding exposure to air and moisture. The oxygen annealing is conducted by introducing a controlled amount of oxygen into the vacuum chamber, creating a localized oxygen-rich environment for annealing while maintaining overall vacuum conditions that prevent interface trap formation.
2Reliability
If in-situ oxygen annealing is performed on the absorber layer, then selenium vacancies are passivated and quantum efficiency is improved, but the process complexity increases
Solution Approach 1:
The patent merges the deposition and annealing processes by performing in-situ oxygen annealing within the same vacuum chamber used for CIGS deposition. This combination eliminates the need for separate annealing equipment and atmospheric control systems, reducing overall process complexity while achieving the benefits of oxygen annealing for passivating selenium vacancies.
Solution Approach 2:
The patent changes the oxygen partial pressure parameter during the annealing process, introducing a controlled amount of oxygen into the vacuum chamber to create an oxygen-rich environment for annealing, then removing the oxygen after annealing. This dynamic parameter control enables effective selenium vacancy passivation while maintaining process simplicity through a single-chamber system.
3Ease of manufacture
If the absorber layer is exposed to moisture in the environment, then the manufacturing process can proceed, but electron recombination increases and charge collection degrades
Solution Approach 1:
The patent maintains the CIGS absorber layer in a vacuum (inert) environment throughout the deposition and annealing processes, preventing exposure to moisture and air. This inert environment atmosphere eliminates the formation of interface traps and prevents electron recombination, while the process remains feasible through in-situ processing within the vacuum chamber.
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 enhances the quantum efficiency of the CIGS films and photovoltaic devices by reducing electron recombination, improving charge collection, and maintaining high sensitivity, with quantum efficiency greater than 50% achievable.
Implementation Method 1
performing physical vapor deposition to deposit an absorber layer comprising an absorber material over a substrate. The physical vapor deposition of the absorber layer may be performed in vacuum.
Implementation Method 2
performing in-situ oxygen annealing of the absorber layer
Data Source
AI summary
A method includes forming, on a substrate by performing physical vapor deposition in vacuum, an absorber layer including copper (Cu), indium (In), gallium (Ga) and selenium (Se), forming a stack including the substrate and an oxygen-annealed absorber layer by performing in-situ oxygen annealing of the absorber layer to improve quantum efficiency of the image sensor by passivating selenium vacancies due to dangling bonds, and forming a cap layer over the oxygen-annealed absorber layer by performing physical vapor deposition in vacuum. The cap layer includes at least one of: Ga2O3·Sn, ZnS, CdS, CdSe, ZnO, ZnSe, ZnIn2Se4, CuGaS2, In2S3, MgO, or Zn0.8Mg0.2O.