CdTe Solar Cell Annealing for Defect Reduction
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Solution Overview
Problem
Thin-film solar cells, particularly those using the CdTe layer, suffer from a high number of crystal defects that reduce the lifetime and concentration of charge carriers, leading to inefficiencies in energy conversion.
Innovation Solution
An additional temperature step is introduced after activating the CdTe layer and removing the residual activation agent, with the substrate being heated to a controlled temperature (180°C to 380°C) for a specific duration (5 minutes to 60 minutes) in a vacuum or inert gas atmosphere, to reduce crystal defects and enhance diffusion processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CdTe layer is activated by exposure to high temperature (380°C to 440°C) for a set duration, then the activation of the CdTe layer is improved, but crystal defects are formed which decrease the lifetime and concentration of charge carriers
Solution Approach 1:
The patent applies a preliminary chloride treatment to the CdTe layer before the main activation step. This pre-treatment modifies theCdTe surface and crystal structure in advance, making it more resistant to defect formation during subsequent high-temperature activation. The chloride ions penetrate theCdTe layer and facilitate better crystal growth and defect annealing during the activation process.
Solution Approach 2:
The patent changes the chemical composition parameters of theCdTe layer by introducing chloride ions through wet-chemical treatment or vapor phase deposition. This compositional modification (adding Cl to CdTe) fundamentally alters the material properties, reducing crystal defects and improving charge carrier concentration while maintaining the benefits of high-temperature activation.
2Manufacturing precision
If wet-chemical etching is performed on the CdTe layer to form a Te-rich layer, then the surface treatment is improved, but the process complexity and time consumption increase
Solution Approach 1:
The patent extracts or removes the separate wet-chemical etching step from the conventional process sequence. Instead of performing etching as a distinct step after activation, the chloride treatment is integrated into the activation process itself, combining multiple functions (activation, surface treatment, and defect reduction) into a single unified step.
Solution Approach 2:
The patent merges the chloride treatment and activation steps into a single integrated process. The chloride-containing atmosphere or solution serves both to activate theCdTe layer and to perform the surface treatment that would otherwise require separate etching steps, thereby simplifying the overall manufacturing process.
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 method significantly reduces crystal defects in the CdTe layer, improving the electric efficiency of the solar cell by up to 0.9 percentage points, thereby enhancing the overall performance of the solar cell.
Implementation Method 1
an additional temperature step is introduced after activating the CdTe layer and removing the residual activation agent, with the substrate being heated to a controlled temperature (180°C to 380°C) for a specific duration (5 minutes to 60 minutes) in a vacuum or inert gas atmosphere, to reduce crystal defects and enhance diffusion processes
Implementation Method 2
enhance diffusion processes
Data Source
Figure 1~2
AI summary
The present invention refers to a method for producing CdTe thin-film solar cells,respectively a semi-finished CdTe thin-film solar cell, where in an additional temperature step is carried out after applying the CdTe layer on to a substrate.In particular, the temperature step is performed after activating the CdTe layer using a suitable activation agent and removing the residual activation agent from the CdTe layer. The temperature treatment is performed under vacuum or in a heating chamber filled with either air or inert gas, during which treatment the substrate is exposed to a temperature between 180°C and 380°C for a time between 5 minutes and 60 minutes. Due to the inventive additional temperature step, the number and extension of crystal defects in the CdTe layer is reduced and the electric efficiency of the solar cell is further improved.