Matter
·
2024
·
IF 17.3
Xuechun Sun,Pengju Shi,Jiahui Shen,Jichuang Shen,Liuwen Tian,Jiazhe Xu,Qingqing Liu,Yuan Tian,Donger Jin,Xiaohe Miao,Jingjing Xue,Rui Wang
Compressive strain is often considered as a key factor in stabilizing formamidinium (FA)-based perovskites. However, the compression along which direction stabilizes perovskite remains unclear due to the presence of non-uniform strain within the material. Here, we introduce a metal encapsulation method to apply compressive strain along the in-plane or out-of-plane direction of perovskite film. According to the grazing-incidence wide-angle X-ray scattering (GIWAXS) results, in-plane compression enhances the stability of perovskites, whereas out-of-plane compression has a detrimental effect. Specifically, out-of-plane compression can lead to the formation of an inactive δ-phase, which compromises the stability of the perovskite. Finally, we develop a general process to integrate in-plane compression into perovskite solar cell (PSC) devices, thereby improving their stability. Our study clarifies the mechanism by which compressive strain affects perovskite stability, offering valuable guidance for strain engineering to optimize perovskite performance.
研究领域:
材料科学
·
光伏技术
✓ 已验证
DOI
高影响因子
MACROMOLECULES
·
2024
·
IF 5.1
Jianfei Xia,Lingling Ni,Chang Zeng,Bao Wang,Rui Zhang,Chenxuan Sun,Jian Song,Junfeng Liu,Chengtao Yu,Ying Zheng,Pengju Pan
Terephthalic polyesters are important engineering plastics and can crystallize into multiple crystal phases, including the mesophase in processing. However, the formation process and structural characteristics for the unique long-range ordered mesophase of terephthalic polyesters are still not well understood. Herein, we investigated the crystal polymorphism, crystallization kinetics, phase transition, and mechanical properties of a medium-chain terephthalic polyester, poly(hexamethylene terephthalate) (PHT). A new long-range ordered mesophase (named as the δ phase) is discovered for PHT during quiescent melt crystallization at a low crystallization temperature (Tc = 10–30 °C). However, the α and β crystal phases are crystallized at a medium (40–80 °C) and high (90–130 °C) Tc, respectively. The mesomorphic δ phase has a long-range order with a layered structure and inclined chain packing, which shows faster chain relaxation and smaller lamellar thickness than the α and β phases. The mesomorphic δ phase is metastable and converts into the stable β phase upon heating or high-temperature annealing. Mechanical properties of PHT can be well tuned by crystal polymorphs. The mesomorphic δ phase of PHT has good transparency and ductility, while the α and β phases possess a higher yield strength and modulus. This work provides an in-depth understanding of the mesophase formation and complex crystal polymorphism of terephthalic polyesters.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
Small
·
2021
·Vol. 17
·期 45
·2104557
·
IF 13.281
Guolong Wang,Yaling Wang,Boyuan Guan,Jiamei Liu,Yan Zhang,Xiaowei Shi,Cheng Tang,Guohong Li,Yingbo Li,Xiao Wang,Lei Li
MnO 2 -based material is one of the most promising cathode candidates of aqueous zinc-ion batteries (ZIBs), but its commercialization is hindered by the sluggish reaction kinetics and poor structural stability. Herein, a hierarchical framework consisting of core–shell structured carbon nanotubes@K-birnessite-MnO 2 enwrapped by graphene/carbon black bicomponent networks (CNT@KMO@GC) via a simple method for ZIBs is designed and developed. The hierarchical framework characterized with favorable K + preintercalation, δ-phase, and vertically aligned nanoflake arrays of KMO and 3D electrically conductive network shows the enhanced electronic/ionic conductivity and improved wettability with electrolyte, resulting in the fast charge/mass transport and stable structural stability of CNT@KMO@GC. When used as cathode in ZIBs, CNT@KMO@GC exhibits exciting electrochemical performance with remarkable capacity (405.5 mAh g −1 at 0.30 A g −1 ), high rate performance (166.6 mAh g −1 up to 10.0 A g −1 ), and impressive cycling stability (almost no capacity decay after 2000 cycles and 77.3% retention after 10 000 cycles at 10.0 A g −1 ). The energy storage mechanism of CNT@KMO@GC is clarified as H + /Zn 2+ coinsertion/extraction via electrochemical analysis and ex situ characterization. This study offers an innovative paradigm for the advance of ZIBs.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
PubMed
高影响因子
ACS Applied Materials & Interfaces
·
2025
·
IF 8.2
Siming Shen,Wenyan Zhao,Yumin Liu,Zhiyang Jv,Anita Achiamaa Bonsu,Liangping Zhu,Wenying Jiang,Kun Li,Shaojian Fu,Pengzhang Li,Hongshi Li,Changan Wang,Zhipeng Xie,Chuanjin Tian
Carbon-based perovskite solar cells (C-PSCs) hold great prospects for commercialization due to their lower manufacturing cost and better stability when compared with metal electrode perovskite. Nevertheless, their power conversion efficiency (PCE) is lower than those of metal-based perovskite solar cells because of the inadequate interface contact between the carbon electrode and the perovskite layer. In this study, the hole transport layer (HTL)-free carbon-based perovskite configuration is utilized to further reduce the cost, and the methylammonium chloride (MACl) additive is introduced to passivate the defects of the perovskite and enhance the interface contact performance. The results indicate that the MACl additive can improve the crystal quality of the perovskite film, reduce the density of defect states, fill the vacancies of the iodide ion, and inhibit the formation of the δ-phase. The optimized C-PSC exhibits an increased carrier lifetime, resulting in improved stability and PCE, with a champion efficiency of 18.04%. Additionally, the device demonstrates ultrahigh photoelectrical stability during continuous light illumination. The unpackaged device with the MACl additive retained 80% of its initial PCE after being operated for 1000 h under double 85 conditions (i.e., at 85 relative humidity (RH) and 85 °C). This work provides an extremely effective strategy for optimizing the interface contact of carbon-based perovskites and preventing the formation of the δ-phase, thereby leading to more efficient and stable optoelectronic devices.
研究领域:
材料科学
·
能源技术
·
光电子学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2019
·
IF 4.175
Qi Wang,Lijun Wang,Yanhui Sun,Aimin Zhao,Wei Zhang,Jianmin Li,Hongbiao Dong,Kuochih Chou
The influence of Ce addition on the precipitation of ferrite (δ) and sigma (σ) phase in super-austenitic stainless steels during solidification was investigated via a combined experimental and theoretical approach. Thermodynamic calculations reveal that the secondary phase of δ and σ are precipitated in sequence near the end of the solidification process due to the segregation of Mo and Cr. The Ce addition improves the thermal stability of the δ, expands the range of Mo content for δ phase precipitation and increases the δ fraction in the solidified structure in the Gulliver–Scheil model. Experimental observation shows that a small addition of Ce accelerates δ nucleation in the interdendritic solute-rich liquid, refines the solidified structure and reduces Mo and Cr segregation, which suppresses precipitation of the σ phase. The σ phase precipitation is replaced by δ phase precipitation after a Ce addition of 0.016%. The change in the secondary phase from σ to δ shortens the time required for homogenization and reduces the nano-hardness of the interdendritic secondary phase, which is significant for hot working.
研究领域:
材料科学
·
金属学与热处理
·
物理冶金
·
合金设计
·
凝固理论
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2025
·
IF 13.2
Xian Xie,Yanzhuo Gou,Kai Zhang,Wei Zhang,Jiaqi Zhang,Jie Liu,Shihao He,Jinhua Li,Xianbao Wang,Liangyou Lin
The δ-phase of formamidinium lead iodide (FAPbI 3 ) is widely regarded as detrimental to achieving high efficiency and stability in perovskite solar cells (PSCs) due to its lack of optical activity. In fact, the δ-FAPbI 3 is crucial for the crystal growth of α-FAPbI 3 and establishing a Type-I band alignment with the α-phase FAPbI 3 in PSCs. In this work, we proposed that 1-(4-pyridyl) piperazine (PPDA) not only can successfully achieve controllable modulation of the α-phase/δ-phase ratio in FAPbI 3 , but also increase the transition temperature of δ-FAPbI 3 to α-FAPbI 3 through strong hydrogen bonding interaction. Moreover, we observed that with increasing annealing temperature, the breakage of hydrogen bonds between PPDA and FA + facilitates the complete phase transition from δ-FAPbI 3 to α-FAPbI 3 , while the liberated PPDA molecules preferentially adsorb onto the (110) facet of α-FAPbI 3 , promoting its oriented growth. Based on this strategy, the PPDA-treated device achieved a power conversion efficiency (PCE) of 23.31 %, which was further improved to 24.81 % after passivation treatment, which is one of the highest PCE among PSCs dominated by (110) preferred orientation and δ-phase modulation. Moreover, the devices exhibited remarkable operational stability, maintaining 87.4 % of its initial performance after 1150 h of storage without encapsulation. These findings underscore the importance of rational δ-phase regulation, presenting a synergistic design strategy that provides new theoretical insights and practical approaches for the development of high-performance PSCs.
研究领域:
材料科学
·
光伏技术
·
纳米结构调控
·
能源材料
·
表面化学
·
晶体工程
·
功能材料
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED MATERIALS
·
2019
·Vol. 31
·期 25
·1901284
·
IF 25.809
Minchao Qin,Kinfai Tse,Tsz-Ki Lau,Yuhao Li,Chun-Jen Su,Guang Yang,Jiehuan Chen,Junyi Zhu,U-Ser Jeng,Gang Li,Hongzheng Chen,Xinhui Lu
Mixed perovskites have achieved substantial successes in boosting solar cell efficiency, but the complicated perovskite crystal formation pathway remains mysterious. Here, the detailed crystallization process of mixed perovskites (FA 0.83 MA 0.17 Pb(I 0.83 Br 0.17 ) 3 ) during spin-coating is revealed by in situ grazing-incidence wide-angle X-ray scattering measurements, and three phase-formation stages are identified: I) precursor solution; II) hexagonal δ-phase (2H); and III) complex phases including hexagonal polytypes (4H, 6H), MAI–PbI 2 –DMSO intermediate phases, and perovskite α-phase. The correlated device performance and ex situ characterizations suggest the existence of an “annealing window” covering the duration of stage II. The spin-coated film should be annealed within the annealing window to avoid the formation of hexagonal polytypes during the perovskite crystallization process, thus achieving a good device performance. Remarkably, the crystallization pathway can be manipulated by incorporating Cs + ions in mixed perovskites. Combined with density functional theory calculations, the perovskite system with sufficient Cs + will bypass the formation of secondary phases in stage III by promoting the formation of α-phase both kinetically and thermodynamically, thereby significantly extending the annealing window. This study provides underlying reasons of the time sensitivity of fabricating mixed-perovskite devices and insightful guidelines for manipulating the perovskite crystallization pathways toward higher performance.
研究领域:
材料科学
·
光伏技术
·
晶体学
·
薄膜制备
·
X射线散射
✓ 已验证
DOI
高影响因子
Nature Photonics
·
2020
·Vol. 15
·期 3
·238-244
·
IF 31.241
Chen Jiawei,Wang Jian,Xu Xiaobao,Li Jinhang,Song Jizhong,Lan Si,Liu Sinan,Cai Bo,Han Boning,Precht Jake T.,Ginger David,Zeng Haibo
At present, electric lighting accounts for ~15% of global power consumption and thus the adoption of efficient, low-cost lighting technologies is important. Halide perovskites have been shown to be good emitters of pure red, green and blue light, but an efficient source of broadband white electroluminescence suitable for lighting applications is desirable. Here, we report a white light-emitting diode (LED) strategy based on solution-processed heterophase halide perovskites that, unlike GaN white LEDs, feature only one broadband emissive layer and no phosphor. Our LEDs operate with a peak luminance of 12,200 cd m −2 at a bias of 6.6 V and a maximum external quantum efficiency of 6.5% at a current density of 8.3 mA cm −2 . Systematic in situ and ex situ characterizations reveal that the mechanism of efficient electroluminescence is charge injection into the α phase of CsPbI 3 , α to δ charge transfer and α–δ balanced radiative recombination. Future advances in fabrication technology and mechanistic understanding should lead to further improvements in device efficiency and luminance.
研究领域:
材料科学
·
光电技术
·
半导体物理
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）