| 1. |
- Pei, Yuan, et al.
(author)
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Dynamic algorithm for fitness function greatly improves the optimization efficiency of frequency selective surface for better design of radar
- 2022
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In: Scientific Reports. - : Nature Portfolio. - 2045-2322. ; 12:1
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Journal article (peer-reviewed)abstract
- Multiple objectives optimization of frequency selective surface (FSS) structures is challenging in electromagnetic wave filter design. For example, one of the sub-objectives, the sidelobe level (SLL), is critical to directional anti-interference, which is complicated and becomes the bottleneck for radar design. Here, we established a dynamic algorithm for fitness function to automatically adjust the weights of multiple objectives in the optimization process of FSS structures. The dynamic algorithm could efficiently evaluate the achieving probability of sub-objectives according to the statistical analysis of the latest individual distribution so that the fitness function could automatically adjusted to focus on the sub-objective difficult to optimize, such as SLL. Computational results from the dynamic algorithm showed that the efficiency of multi-objective optimization was greatly improved by 213%, as compared to the fixed-weighted algorithm of the fitness function. Specifically for SLL, the efficiency rate increased even better, up to 315%. More interestingly, the FSS structures were most improved while picking median value or golden section value as the reference value. Taken together, the current study indicated that the dynamic algorithm with fitness function might be a better choice for FSS structural optimization with SLL suppression and potentially for the better design of lower SLL radar.
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| 2. |
- Yu, Xianxi, et al.
(author)
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Memory Devices via Unipolar Resistive Switching in Symmetric Organic-Inorganic Perovskite Nanoscale Heterolayers
- 2020
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In: ACS Applied Nano Materials. - : AMER CHEMICAL SOC. - 2574-0970. ; 3:12, s. 11889-11896
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Journal article (peer-reviewed)abstract
- Organic-inorganic hybrid perovskite thin films with nanostructured polycrystalline grains have shown great potential in various nanoscale optoelectrical applications. Among them, the field of electrical memory has fallen behind due to insufficient knowledge of the related resistive switching characters and mechanisms. In the present work, switching behaviors of perovskite memory devices are systematically analyzed by comparing them with organic memory devices. We found that decreasing the conductivity of a polycrystalline perovskite thin layer would lead to unipolar switching behaviors, which is supplementary to the present perovskite memory family where bipolar switching is commonly reported. Moreover, our proposed symmetrical device with a nanoscale heterolayer structure enables us not only to achieve highly reproducible unipolar switching devices but also to settle the argument whether microconducting channels exist within perovskite memory devices through characterizing the microscopic morphological homogeneity. Surprisingly, the scanning electron microscopy results show that partial 10 pm large perovskite grains would be decomposed into various 100 nm small grains under high external bias, indicating the presence of microconducting channels. Furthermore, energy-dispersive X-ray spectroscopy results together with photoluminescence results of the perovskite thin film before and after applying bias are nearly identical, demonstrating that microconducting channels are formed without any difference in compositions or optical properties. Our discoveries provide a practical strategy to achieve electrical storage via organic-inorganic hybrid perovskite thin-film devices.
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| 3. |
- Cai, Xia, et al.
(author)
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Data-driven design of high-performance MASn(x)Pb(1-x)I(3) perovskite materials by machine learning and experimental realization
- 2022
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In: Light. - : Springer Nature. - 2095-5545 .- 2047-7538. ; 11:1
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Journal article (peer-reviewed)abstract
- The photovoltaic performance of perovskite solar cell is determined by multiple interrelated factors, such as perovskite compositions, electronic properties of each transport layer and fabrication parameters, which makes it rather challenging for optimization of device performances and discovery of underlying mechanisms. Here, we propose and realize a novel machine learning approach based on forward-reverse framework to establish the relationship between key parameters and photovoltaic performance in high-profile MASn(x)Pb(1-x)I(3) perovskite materials. The proposed method establishes the asymmetrically bowing relationship between band gap and Sn composition, which is precisely verified by our experiments. Based on the analysis of structural evolution and SHAP library, the rapid-change region and low-bandgap plateau region for small and large Sn composition are explained, respectively. By establishing the models for photovoltaic parameters of working photovoltaic devices, the deviation of short-circuit current and opencircuit voltage with band gap in defective-zone and low-bandgap-plateau regions from Shockley-Queisser theory is captured by our models, and the former is due to the deep-level traps formed by crystallographic distortion and the latter is due to the enhanced susceptibility by increased Sn (4+ )content. The more difficulty for hole extraction than electron is also concluded in the models and the prediction curve of power conversion efficiency is in a good agreement with Shockley-Queisser limit. With the help of search and optimization algorithms, an optimized Sn:Pb composition ratio near 0.6 is finally obtained for high-performance perovskite solar cells, then verified by our experiments. Our constructive method could also be applicable to other material optimization and efficient device development.
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| 4. |
- Zhang, Xin, et al.
(author)
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Minimizing the Interface-Driven Losses in Inverted Perovskite Solar Cells and Modules
- 2023
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In: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; , s. 2532-2542
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Journal article (peer-reviewed)abstract
- The inverted p-i-n perovskite solar cells hold high promise for scale-up toward commercialization. However, the interfaces between the perovskite and the charge transport layers contribute to major power conversion efficiency (PCE) loss and instability. Here, we use a single material of 2-thiopheneethylammonium chloride (TEACl) to molecularly engineer both the interface between the perovskite and fullerene-C60 electron transport layer and the buried interface between the perovskite and NiOx-based hole transport layer. The dual interface modification results in optimized band alignment, suppressed nonradiative recombination, and improved interfacial contact. A PCE of 24.3% is demonstrated, with open-circuit voltage (Voc) and fill factor (FF) of 1.17 V and 84.6%, respectively. The unencapsulated device retains >97.0% of the initial performance after 1000 h of maximum power point tracking under illumination. Moreover, a PCE of 22.6% and a remarkable FF of 82.4% are obtained for a mini-module with an active area of 3.63 cm2.
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