Asymmetric Thermal Gradient for Polyimide Substrate CIS Deposition
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Solution Overview
Problem
Conventional thin-film photovoltaic devices on flexible polyimide substrates face challenges due to thermal gradients and substrate degradation during high-temperature CIS/CIGS deposition, leading to reduced efficiency and manufacturing yield, as well as susceptibility to electrical shorting from defects in dielectric coatings.
Innovation Solution
Heating the front outer surface of the polyimide substrate instead of the back surface during CIS/CIGS deposition, combined with radiant heating from zone boundary heaters and the use of high emittance coatings to minimize substrate heating and prevent electrical shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the back surface of the polyimide substrate is heated during CIS/CIGS deposition, then the substrate temperature increases to enable the deposition reaction, but the front surface temperature becomes excessive causing substrate degradation and reduced manufacturing yield
Solution Approach 1:
The heating function is segmented into two independent heating zones: a first heater for the back surface and a second heater for the front surface. This allows independent temperature control of each surface, enabling the substrate temperature to be sufficient for deposition while preventing excessive front surface temperature that causes degradation.
Solution Approach 2:
Different temperature conditions are applied to different locations of the substrate. The back surface receives higher temperature heating to enable the deposition reaction, while the front surface is controlled to a lower temperature to prevent substrate degradation. This local differentiation of thermal conditions resolves the contradiction between achieving sufficient substrate temperature and preventing excessive heating.
2Reliability
If a dielectric coating is applied to the front surface to prevent electrical shorting, then electrical isolation is achieved, but the coating is susceptible to damage during high-temperature deposition processes
Solution Approach 1:
The heating function is segmented into two independent heating zones: a first heater for the back surface and a second heater for the front surface. This allows independent temperature control of each surface, enabling the substrate temperature to be sufficient for deposition while preventing excessive front surface temperature that causes substrate degradation.
Solution Approach 2:
Different temperature conditions are applied to different locations of the substrate. The back surface receives higher temperature heating to enable the deposition reaction, while the front surface is controlled to a lower temperature to prevent substrate degradation.
3Ease of manufacture
If uniform heating is applied to the substrate, then thermal processing is simplified, but thermal energy is wasted heating areas outside the deposition zone
Solution Approach 1:
Different temperature conditions are applied to different locations of the substrate. The back surface receives higher temperature heating to enable the deposition reaction, while the front surface is controlled to a lower temperature to prevent substrate degradation.
Solution Approach 2:
The heating system is made dynamically controllable with independent temperature regulation for different zones. The first and second heaters can be independently adjusted to provide optimal temperature profiles during deposition, allowing energy-efficient localized heating rather than uniform heating of the entire substrate.
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 CIS/CIGS reaction, reduces substrate degradation, and improves manufacturing yield by confining thermal energy to the deposition area, while also preventing electrical shorting and maintaining high emittance coatings for efficient heat radiation.
Implementation Method 1
heating the front outer surface of the flexible polyimide substrate using one or more radiant heat generating elements
Implementation Method 2
heating the flexible polyimide substrate such that a temperature of the front outer surface of the flexible polyimide substrate is higher than a temperature of the back outer surface of the flexible polyimide substrate
Implementation Method 3
use of high emittance coatings to minimize substrate heating and prevent electrical shorting
Data Source
AI summary
A method for depositing one or more thin-film layers on a flexible polyimide substrate having opposing front and back outer surfaces includes the following steps: (a) heating the flexible polyimide substrate such that a temperature of the front outer surface of the flexible polyimide substrate is higher than a temperature of the back outer surface of the flexible polyimide substrate, and (b) depositing the one or more thin-film layers on the front outer surface of the flexible polyimide substrate. A deposition zone for executing the method includes (a) one of more physical vapor deposition sources adapted to deposit one or more metallic materials on the front outer surface of the substrate, and (b) one or more radiant zone boundary heaters.