Graded SnOx Electron Transport Layer for Higher Perovskite Cell Fill Factor
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Solution Overview
Problem
Perovskite solar cells face challenges with low fill factor (FF) and energy conversion efficiency due to the electron transport layer's high resistance against electron migration and p-type semiconductor characteristics, particularly in thin films like SnO binding layers.
Innovation Solution
The electron transport layer is designed as a graded thin film where the chemical binding state between elements gradually changes from the lower to the upper portion, using materials such as SnOx to SnO2, formed through atomic layer deposition (ALD), with specific flow rates and oxygen sources to optimize the film's composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin film electron transport layer (e.g., SnO binding layer) is used in perovskite solar cells, then the device structure is simplified and manufacturing is easier, but the fill factor and energy conversion efficiency deteriorate due to high resistance against electron migration and p-type semiconductor characteristics
Solution Approach 1:
The electron transport layer is divided into multiple sub-layers with different compositions and functions. The lower layer (closer to perovskite) has one composition optimized for electron extraction, while the upper layer has a different composition optimized for electron transport to the electrode. This segmentation allows each sub-layer to be optimized for its specific function, resolving the contradiction between ease of manufacture and performance.
Solution Approach 2:
Different regions of the electron transport layer are given different local properties. The lower portion has properties optimized for interfacing with perovskite (e.g., specific band alignment, composition), while the upper portion has properties optimized for electron collection and transport. This local quality variation enables the layer to simultaneously achieve good electron extraction and transport, improving fill factor without complicating manufacturing.
2Device complexity
If a thin film electron transport layer is used, then the device structure is simplified, but the energy conversion efficiency deteriorates due to high resistance against electron migration
Solution Approach 1:
The electron transport layer is constructed as a composite structure with multiple materials or compositions. By combining materials with complementary properties (e.g., one material excellent for electron extraction, another for electron transport), the composite layer achieves both low resistance and simplified device architecture, improving energy conversion efficiency without significantly increasing device complexity.
Solution Approach 2:
The composition, thickness, or other parameters of the electron transport layer are varied across different regions or through controlled gradients. This parameter optimization allows the layer to achieve optimal electron transport properties while maintaining a relatively simple device structure, thereby improving energy conversion efficiency without excessive complexity.
3Ease of manufacture
If a conventional electron transport layer with uniform composition is used, then the manufacturing process is simpler, but the performance is limited due to inability to optimize different functions at different locations
Solution Approach 1:
The electron transport layer is designed with dynamic or variable properties rather than uniform composition. This could involve graded composition, thickness variations, or functional zonation that allows the layer to adapt its properties across different regions. Such dynamics enable simultaneous optimization of electron extraction and transport functions, improving energy conversion efficiency while maintaining manufacturability through systematic design approaches.
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 graded thin film structure significantly improves the fill factor and energy conversion efficiency of perovskite solar cells, achieving higher performance compared to monolayer films.
Implementation Method 1
the electron transport layer is a graded thin film in which a chemical binding state between elements constituting the electron transport layer gradually changes from a lower portion of the graded thin film to an upper portion thereof
Data Source
AI summary
The present invention relates to a perovskite solar cell and a tandem solar cell comprising the same, characterized in that the perovskite solar cell comprises: a substrate; a transparent electrode; a hole transport layer; a perovskite light absorption layer; an electron transport layer; and a metal electrode, wherein the electron transport layer is a graded thin film in which a chemical binding state of elements constituting the electron transport layer gradually changes from the lower portion thereof toward the upper portion thereof.