Backside Contact Solar Cell Anti-Reflective Coating UV Stability
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Solution Overview
Problem
Backside contact solar cells face efficiency reduction and reliability issues due to UV radiation degrading the front side passivation, leading to increased recombination of electrons and holes at the SiO2/Si interface.
Innovation Solution
A multilayer anti-reflection structure is formed on the front side of the solar cell, comprising a passivation layer of thermally grown silicon dioxide, a high optical absorption layer such as amorphous silicon or high-k silicon nitride to block UV radiation, and a low optical absorption layer like low-k silicon nitride, which filters out UV radiation while minimizing impact on visible light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer anti-reflection structure is used, then the manufacturing process is simple, but UV radiation degrades the front side passivation leading to increased recombination
Solution Approach 1:
The anti-reflection structure is divided into multiple functional layers: a first anti-reflection layer (silicon nitride) for UV filtering and a second anti-reflection layer (silicon oxide) for passivation. This segmentation allows each layer to perform its specific function optimally, with the silicon nitride layer blocking UV radiation before it reaches the passivation layer, thereby preventing UV-induced degradation while maintaining manufacturing feasibility.
Solution Approach 2:
The invention uses a composite multi-layer structure combining different materials (silicon nitride and silicon oxide) with complementary properties. The silicon nitride layer provides high UV absorption due to its bandgap characteristics, while the silicon oxide layer provides excellent passivation properties. This composite approach resolves the contradiction by achieving enhanced UV stability through material composition rather than increasing overall structural complexity.
2Reliability
If a high optical absorption layer is added to block UV radiation, then UV stability improves, but the structure becomes more complex
Solution Approach 1:
The silicon nitride layer serves multiple functions simultaneously: it acts as an anti-reflection coating to reduce overall reflection losses, functions as a UV filter to protect the underlying passivation layer, and provides a stable interface for the second anti-reflection layer. This multi-functionality reduces the need for additional specialized layers, thereby limiting the increase in structural complexity while achieving UV protection.
3Productivity
If the front side is randomly textured to reduce reflection, then solar radiation collection increases, but interface state density between SiO2 and Si increases
Solution Approach 1:
The invention applies different material properties to different locations in the structure: the silicon nitride layer is applied first on the textured surface where it conforms to the local texture geometry, providing UV protection at each local point. The subsequent silicon oxide layer is deposited over this patterned surface, creating localized passivation regions. This local quality approach allows the textured surface to maintain its high light-trapping capability while each local interface region benefits from the protective and passivating layers.
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 solution significantly improves UV stability and maintains solar cell efficiency by reducing UV-induced degradation, with amorphous silicon filtering out a substantial percentage of UV radiation and high-k silicon nitride acting as an effective UV filter without detrimental effects on visible light transmission.
Implementation Method 1
The high optical absorption layer may be configured to block at least 10% of UV radiation coming into the substrate
Implementation Method 2
the low optical absorption layer like low-k silicon nitride, which filters out UV radiation while minimizing impact on visible light absorption
Implementation Method 3
The passivation level may include silicon dioxide thermally grown on a textured surface of the solar cell substrate
Data Source
AI summary
A multilayer anti-reflection structure for a backside contact solar cell. The anti-reflection structure may be formed on a front side of the backside contact solar cell. The anti-reflection structure may include a passivation level, a high optical absorption layer over the passivation level, and a low optical absorption layer over the high optical absorption layer. The passivation level may include silicon dioxide thermally grown on a textured surface of the solar cell substrate, which may be an N-type silicon substrate. The high optical absorption layer may be configured to block at least 10% of UV radiation coming into the substrate. The high optical absorption layer may comprise high-k silicon nitride and the low optical absorption layer may comprise low-k silicon nitride.