Self-powered reduced-dimensionality perovskite photodiodes with controlled crystalline phase and improved stability

Lim, Ju Won,Wang, Huan,Choi, Chi Hun,Kwon, Hannah,Quan, Li Na,Park, Won-Tae,Noh, Yong-Young,Kim, Dong Ha Elsevier 2019 Nano energy Vol.57 No.-

<P><B>Abstract</B></P> <P>In this work, we developed the perovskite photodiodes based on the dimensionality-reduced quasi two-dimensional (Q-2D) photoactive layer structure by incorporating phenylethylammonium iodide (PEAI) into methylammonium lead iodide (MAPbI<SUB>3</SUB>), which effectively enhanced both the crystalline phase and the ambient stability of the perovskite. The Q-2D perovskite photodiode exhibited a dark current of 1.76 × 10<SUP>−7</SUP> A/cm<SUP>2</SUP>, resulting in the detectivity (D*) of 2.20 × 10<SUP>12</SUP> J and responsivity of 0.53 A/W, which is among the highest performance levels without the voltage bias (0 V) due to the systematically optimized perovskite phase resulting in the reduced leakage current. In addition, the current density of Q-2D perovskite photodiode maintained 76% of the initial level current density even after 80 days in the ambient condition, compared to 15% of 3D perovskite photodiode control sample. Such superior performance and stability were mainly attributed to the enhanced degree of crystallization of the Q-2D perovskites, which was confirmed by X-ray diffraction and grazing incidence wide-angle X-ray scattering (GIWAXS) measurement. Also, the improved stability of Q-2D perovskite films was confirmed by both lifetime test and atomic force microscopy studies where the negligible number of pinholes was observed in the quasi-2D perovskite films while considerable deformations were found in the 3D perovskites photodiode. Our study suggests a simple and robust protocol for the development of stable and high-performance perovskite photodetectors via dimensional and constitutional optimization of conventional perovskites for the practical usage of perovskite in the photodiode applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Q-2D perovskite photodiode exhibited the D* of 2.20 × 10<SUP>12</SUP> J and R of 0.53 A/W without the voltage bias (0 V). </LI> <LI> The current density of Q-2D perovskite photodiode maintained 76 % of the initial level while 15 % for the 3D one. </LI> <LI> Grazing incidence wide-angle X-ray scattering (GIWAXS) analysis revealed the origin of the stability improvement. </LI> <LI> Quasi-2D perovskite materials can be promising candidates for stable, tunable and flexible optoelectronic applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Dimensionality-controlled perovskite photodiodes with improved stability were systematically fabricated while retaining the comparable electrical performance of conventional three-dimensional perovskites. The quasi-2D perovskite photodetector exhibited an improved detectivity of 2.20 × 10<SUP>12</SUP> J performance and maintained 76% of initial level while the performance of three-dimensional perovskite photodetector remained only 15% after 80 days. Our study suggests a facile solution for the poor stability of the three-dimensional perovskite, with a potential for the development of highly-stable perovskite optoelectronics.</P> <P>[DISPLAY OMISSION]</P>

Polyethylenimine ethoxylated interlayer-mediated ZnO interfacial engineering for high-performance and low-temperature processed flexible perovskite solar cells: A simple and viable route for one-step processed CH₃NH₃PbI₃

Lim, Ju Won,Wang, Huan,Choi, Chi Hun,Quan, Li Na,Chung, Kyungwha,Park, Won-Tae,Noh, Yong-Young,Kim, Dong Ha Elsevier 2019 Journal of Power Sources Vol.438 No.-

<P><B>Abstract</B></P> <P>Developing perovskite solar cells (PSCs) with high-efficiency and a low-temperature process has great potential for the realization of the scalable, economic, and roll-to-roll based renewable energy conversion devices. ZnO has been recognized as the promising electron transport layer (ETL) that may overcome the limitations of the conventional TiO<SUB>2</SUB>. However, methylammonium lead iodide (MAPbI<SUB>3</SUB>) perovskite is prone to decomposition at the ZnO surface, which hinders the development of simple one-step deposition of perovskite, resulting in the limited photovoltaic performance. Herein, we report interlayer mediated efficient ETLs for viable flexible PSCs. The utilization of polyethyleneimine ethoxylated layer on ZnO prevents the direct contact between the perovskite and ETLs, avoiding the photoactive layer decomposition. Thus, interlayer-mediated PSCs show higher efficiency with enhanced stability by decreasing the electron transport barrier. As a result, the PSC employing tailor-designed ETL interfaces exhibited average power conversion efficiency (PCE) of 15.8%, which was superior by 25.4% to that of a control device (12.6%). With our strategy, we further demonstrated PSCs on flexible substrates which exhibit an average PCE of 11.9% under low-temperature fabrication. The new interface engineering strategy may pave the way to the realization of high performance, easy-to-process, and large-area perovskite optoelectronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Universal interface engineering technique for highly stable flexible PSCs. </LI> <LI> The in-depth investigation into the enhanced stability and high-efficiency PSCs. </LI> <LI> Interlayer mediated PSC exhibits 15.8% PCE, superior by 25.4% to control device. </LI> <LI> Low-temperature processed PSCs for the next-generation renewable energy sources. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Analysis and optimization of a typical quasi-zero stiffness vibration isolator

Huan Li,Yang Yu,Jianchun Li,Yancheng Li 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.3

To isolate vibration at a low-frequency range and at the same time to provide sufficient loading support to the isolated structure impose a challenge in vibration isolation. Quasi-zero stiffness (QZS) vibration isolator, as a potential solution to the challenge, has been widely investigated due to its unique property of high-static & low-dynamic stiffness. This paper provides an in-depth analysis and potential optimization of a typical QZS vibration isolator to illustrate the complexity and importance of design optimization. By carefully examining the governing fundamentals of the QZS vibration isolator, a simplified approximation of force and stiffness relationship is derived to enable the characteristic analysis of the QZS vibration isolator. The explicit formulae of the amplitude-frequency response (AFR) and transmissibility of the QZS vibration isolator are obtained by employing the Harmonic Balance Method. The transmissibility curves under force excitation with different values of nonlinear coefficient, damping ratio, and amplitude of excitation are further investigated. As the result, an optimization of the structural parameter has been demonstrated using a comprehensive objective function with considering multiple dynamic characteristic parameters simultaneously. Finally, the genetic algorithm (GA) is adopted to minimise the objective function to obtain the optimal stiffness ratios under different conditions. General recommendations are provided and discussed in the end.

Design and Construction of Polyaniline/Reduced Graphene Oxide Three-Dimensional Dendritic Architecture on Interdigital Electrode for Sensitive Detection Nitrite

Li Li,Huan Liu,Boya Li,Yanan Guo,Liming Qing,Baohui Wang 한국고분자학회 2020 Macromolecular Research Vol.28 No.5

The polyaniline/reduced graphene oxide (PANI/RGO) modified interdigital electrode (IDE) has been successfully fabricated by in situ electrochemical reduction and electrochemical polymerization through cyclic voltammetry. The morphology and topography of PANI/RGO characterized by SEM and AFM display intercrosslinked dendritic structure in three dimensions, and it is favorable for the detection of nitrite due to its large surface area, which can provide the large electrocatalytic active surface and various diffusion paths for nitrite. Herein, the obtained PANI/ RGO/IDE was employed for the electrochemical monitoring platform of nitrite for the first time and the electrochemical performance of the as-developed sensor was investigated via cyclic voltammetry and chronoamperometry. At the optimum conditions, the PANI/RGO/IDE has a linear response in the range from 0.4 to 183.7 mM with a sensitivity of 457.4 μA mM-1 cm-2 and a detection limit of 0.1 μM. Moreover, the obtained PANI/RGO/IDE with excellent long-term stability and reproducibility also can be employed for practical application for the determination of nitrite in tap water, the results show that the recovery rate is desirable. It is expected that IDE can be employed as the substrate electrode decorated with various materials to construct highperformance electrochemical sensors.

Bevacizumab Regulates Cancer Cell Migration by Activation of STAT3

Wu, Huan-Huan,Zhang, Shuai,Bian, Huan,Li, Xiao-Xu,Wang, Lin,Pu, Yin-Fei,Wang, Yi-Xiang,Guo, Chuan-Bin Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.15

There are numerous clinical cases indicating that long-term use of bevacizumab may increase the invasiveness of tumors. However, to date, little is known about underlying molecular mechanisms. Therefore, the purpose of our study was to investigate effects of bevacizumab in four cancer cells lines (WSU-HN6, CAL27, Tca83, and HeLa). It was found to promote migration and invasion in the WSU-HN6 and Tca83 cases, while exerting inhibitory effects in CAL27 and HeLa cells. The signal transducer and activator of transcription (STAT) 3 inhibitors niclosamide and S3I-201 inhibited the STAT3 signal pathway, which is activated by bevacizumab. These inhibitors also substantially blocked bevacizumab-induced migration of WSU-HN6 and Tca83 cells. Bevacizumab upregulated interleukin (IL)-6 and phosphorylated (p)-STAT3 expression time-dependently. Therefore, we propose that bevacizumab has differential effects on the migration of different cancer cell lines and promotes migration via the IL-6/STAT3 signaling pathway.

Aerodynamic properties of a streamlined bridge-girder under the interference of trains

Huan Li,Xu-hui He,Liang Hu,Xiaojun Wei 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.3

Trains emerging on a streamlined bridge-girder may have salient interference effects on the aerodynamic properties of the bridge. The present paper aims at investigating these interferences by wind tunnel measurements, covering surface pressure distributions, near wake profiles, and flow visualizations. Experimental results show that the above interferences can be categorized into two primary effects, i.e., an additional angle of attack (AoA) and an enhancement in flow separation. The additional AoA effect is demonstrated by the upward-moved stagnation point of the oncoming flow, the up-shifted global symmetrical axis of flow around the bridge-girder, and the clockwise-deflected orientation of flow approaching the bridgegirder. Due to this additional AoA effect, the two critical AoAs, where flow around the bridge-girder transits from trailing-edge vortex shedding (TEVS) to impinging leading-edge vortices (ILEV) and from ILEV to leading-edge vortex shedding (LEVS) of the bridge-girder are increased by 4° with respect to the same bridge-girder without trains. On the other hand, the underlying flow physics of the enhancement in flow separation is the large-scale vortices shedding from trains instead of TEVS, ILEV, and LEVS governed the upper half bridge-girder without trains in different ranges of AoA. Because of this enhancement, the mean lift and moment force coefficients, all the three fluctuating force coefficients (drag, lift, and moment), and the aerodynamic spanwise correlation of the bridge-girder are more significant than those without trains.

Analysis of the Interdecadal and Interannual Variability of Autumn Extreme Rainfall in Taiwan Using a Deep-Learning-Based Weather Typing Approach

Li‑Huan Hsu,Yi‑chao Wu,Chou‑Chun Chiang,Jung‑Lien Chu,Yi‑Chiang Yu,An‑Hsiang Wang,Ben Jong‑Dao Jou 한국기상학회 2023 Asia-Pacific Journal of Atmospheric Sciences Vol.59 No.2

This study sought to assess the interdecadal and interannual variability of autumn extreme rainfall (ER) in Taiwan from 1979to 2019. Three types of ER events were identified based on a clustering analysis augmented by a deep autoencoder-basedneural network model. This method outperforms other methods in obtaining the optimal number of clusters by extractingthe synoptic features in advance. The patterns associated with these three types include a tropical cyclone covering Taiwan(TC), a TC-like circulation in the South China Sea (SCS) accompanied by northeasterly near northern Taiwan (TC-NE), andnortheasterly near northern Taiwan (NE). The differences in the rainfall pattern caused by the three types were discernableover Taiwan. How the PDO or ENSO modulates the regional large-scale environment to favor the occurrence of these ERevents was investigated. The occurrence of TC-NE events was simultaneously correlated with the negative phases of PDO/ENSO in the interdecadal/interannual scale. In the negative phases of PDO/ENSO, a low-level anomalous cyclone overSCS accompanied by background northeasterly favored the regional TC activities and may cause more TC-NE events. Theoccurrence of NE events is simultaneously correlated with the cold phase of ENSO. An anomalous low-level anticyclone inNortheast Asia strengthened the northeasterly toward northern Taiwan, and with the seasonal background moisture, providedfavorable conditions for the occurrence of the NE events. Overall, the occurrence of the TC events did not correlate with thePDO or ENSO signals; the reasons for the lack of correlation were discussed herein.

Significance of Thrombocytosis in Clinicopathologic Characteristics and Prognosis of Gastric Cancer

Li, Fang-Xuan,Wei, Li-Juan,Zhang, Huan,Li, Shi-Xia,Liu, Jun-Tian Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.16

Purpose: We aimed to study the relationship between thrombocytosis and clinical features of gastric cancerfocussing on platelet counts and gastric cancer progression through different TNM stages. Methods: According to the normal range of platelet count in our institution, 1,596 patients were divided to two groups: a thrombocytosis group (120 patients, > $400{\times}1000/{\mu}L$) and a control group (1,476 patients, ${\leq}400{\times}1000/{\mu}L$). Results: The incidence of thrombocytosis was 7.5%. Higher platelet counts were observed in patients with older age, larger tumor size, deeper invasion, lymph node metastasis, distant metastasis and advanced TNM stage. In multivariate logistic regression, tumor size, depth of tumor invasion, lymph node metastasis and TNM stage were independent risk factors for thrombocytosis of gastric cancer patients. On prognostic analysis, age, tumor size, tumor location, histologic type, depth of tumor invasion, lymph node metastasis, distant metastasis and TNM stage and platelet count were important factors. Tumor size, invasion depth, lymph node metastasis, TNM stage and the platelet count were independent prognostic factors. Conclusion: Thrombocytosis is associated with clinical features of gastric cancer patients and correlates with a poor prognosis.

Structure, Microstructure, and Piezoelectric Properties of Ytterbium-Doped Potassium Sodium Niobate Lead-Free Ceramics

Huan Li,Wenlong Yang,Zhongxiang Zhou,Hao Tian 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5

The structure, microstructure, and piezoelectric properties of conventionally sintered Yb-doped K0.5Na0.5NbO3(KNN) lead-free ceramics were investigated. Doping the KNN ceramics with Yb2O3 was effective in inhibiting the grain growth in the KNN ceramics and in densifying the ceramics. The 1.0 wt. % Yb-doped KNN ceramics showed the maximum density, about 96.8% of the theoretical density. X-ray diffraction analysis showed that a small number of Yb3+ ions could be incorporated into the matrix of the ceramicsto occupythe α- or β-sites in the crystal lattice, thereby significantly affecting the piezoelectric properties of the ceramics. Enhanced piezoelectric properties (i.e., d33= 135 pC/N, kp = 34.5%, and Qm = 80.2) were obtained for the 0.50 wt. %Yb-doped KNN ceramics.

Soft and Flexible Bilayer Thermoplastic Polyurethane Foam for Development of Bioinspired Artificial Skin

Li, Huan,Sinha, Tridib K.,Oh, Jeong Seok,Kim, Jin Kuk American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.16

<P>Inspired by the epidermis-dermis composition of human skin, here we have simply developed a lightweight, robust, flexible, and biocompatible single-electrode triboelectric nanogenerator (S-TENG)-based prototype of bilayer artificial skin, by attaching one induction electrode with unfoamed skin layer of microcellular thermoplastic polyurethane (TPU) foam, which shows high-performance object manipulation [by responding differently toward different objects, viz., aluminum foil, balloon, cotton glove, human finger, glass, rubber glove, artificial leather, polyimide, poly(tetrafluoroethylene) (PTFE), paper, and wood], due to electrification and electrostatic induction during contact with the objects having different chemical functionalities. Comparative foaming behavior of ecofriendly supercritical fluids, viz., CO<SUB>2</SUB> over N<SUB>2</SUB> under variable temperatures (e.g., 130 and 150 °C) and constant pressure (15 MPa), have been examined here to pursue the soft and flexible triboelectric TPU foam. The foam derived by CO<SUB>2</SUB> foaming at 150 °C has been prioritized for development of S-TENG. Foam derived by CO<SUB>2</SUB> foaming at 130 °C did not respond as well due to the smaller cell size, higher hardness, and thicker skin. Inflexible N<SUB>2</SUB>-derived foam was not considered for S-TENG fabrication. Object manipulation performance has been visualized by principal component analysis (PCA), which shows good discrimination among responses to different objects.</P> [FIG OMISSION]</BR>