Solar Cell Electrode Stack for Halide Diffusion and Oxidation Resistance
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Solution Overview
Problem
Existing solar cells with inverted structures have room for improvement in conversion efficiency and stability.
Innovation Solution
A photoelectric conversion element with a specific layered structure, including a transparent electroconductive layer, hole transport layer, light absorption layer, electron transport layer, and electrode, where the electrode is composed of stacked Bi, Ti, and Au layers to prevent halide ion diffusion and oxidation, enhancing ohmic contact and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple electrode structure is used, then device complexity is reduced, but conversion efficiency and stability deteriorate
Solution Approach 1:
The electrode is segmented into three distinct layers: a first electroconductive layer (Bi, Ti, or Cr) for ohmic contact and halide ion barrier, a second electroconductive layer (Au, Pt, or C) for electron collection, and an optional third electroconductive layer for enhanced stability. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between simple structure and high reliability.
Solution Approach 2:
The electrode uses composite material structure combining different metals and carbon materials with complementary properties. The first layer (Bi/Ti/Cr) provides low work function and halide ion blocking, the second layer (Au/Pt/C) provides high electrical conductivity and chemical stability, creating a composite electrode that achieves both simplicity and high reliability.
2Ease of manufacture
If a single-layer electrode is used, then manufacturing is simplified, but halide ion diffusion and oxidation occur
Solution Approach 1:
The first electroconductive layer (Bi, Ti, or Cr) acts as an intermediary layer between the electron transport layer and the outer electrode layers. It provides ohmic contact for electron collection while simultaneously serving as a diffusion barrier against halide ions, preventing them from reaching and degrading the outer Au/Pt/C layer.
Solution Approach 2:
The harmful functions of halide ion diffusion and oxidation are extracted and isolated to the first electroconductive layer, which is specifically designed to handle these interactions. This layer takes out the burden of protecting against degradation, allowing the outer layers to focus on electron collection without being affected by harmful factors.
3Productivity
If high conversion efficiency is pursued, then performance improves, but long-term stability deteriorates
Solution Approach 1:
Different regions of the electrode have different local qualities optimized for specific functions. The first layer has low work function and high reactivity for efficient electron collection (boosting conversion efficiency), while the outer Au/Pt/C layer has high chemical stability for long-term durability. This local differentiation allows the electrode to simultaneously achieve high efficiency and long stability.
Solution Approach 2:
The first electroconductive layer provides beforehand cushioning by establishing a stable interface with the electron transport layer and blocking halide ion diffusion paths before degradation can occur. This preventive barrier protects the electrode structure from deterioration during operation, ensuring long-term stability while maintaining high conversion efficiency.
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 achieves high conversion efficiency and long-term stability by preventing halide ion diffusion and oxidation, improving the performance of the solar cell.
Implementation Method 1
the first electroconductive layer is structured to make ohmic contact with the electron transport layer, and to prevent the diffusion of the halide ions towards the second electroconductive layer
Implementation Method 2
the second electroconductive layer is structured to prevent the diffusion of the third electroconductive layer towards the electron transport layer or the light absorption layer
Implementation Method 3
the first electroconductive layer is structured to make ohmic contact with the electron transport layer
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A photoelectric conversion element (1,2) has a transparent electroconductive layer (11), a hole transport layer (12), a light absorption layer (13), an electron transport layer (14), and an electrode (15) stacked in this order; the light absorption layer (13) containing a material that contains a halide ion, and the electrode (15) having a Bi layer (151), a Ti layer or a Cr layer (152), and an Au layer (153) stacked in this order when viewed from the electron transport layer (14). The material contained in the light absorption layer (13) is preferred to further contain silver ion and bismuth ion.