Sushu Wan

University of Wisconsin–Madison

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Yuxi Tian

Nanjing University

Daocheng Hong

Nanjing University

Mingcai Xie

Nanjing University

Weiqing Yang

University of Chinese Academy of Sciences

Hua Yan

Yibin University

Zhihong Wei

Nanjing University

Yu Du

Nanjing University

Hairen Tan

Collaborative Innovation Center of Advanced Microstructures

Siyu Lu

Zhengzhou University

Yajie Zhu

Nanjing University

Cooperative Institutions

Nanjing University

Chinese Academy of Sciences

Collaborative Innovation Center of Advanced Microstructures

University of Chinese Academy of Sciences

State Key Laboratory of Analytical Chemistry for Life Science

Peking University

Wuhan University

Sun Yat-sen University

Beijing Institute of Technology

Institute of Semiconductors

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Effects of local matrix environment on the spectroscopic properties of ensemble to single-particle level carbon dots

Chinese Chemical Letters (2021)

Zhihong Wei Boyang Wang Mingcai Xie Daocheng Hong Xin Yang

Particle (ecology)

Carbon fibers

Matrix (chemical analysis)

10.1016/j.cclet.2021.08.014

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Citations (12)

Effect of micro-uniformity on electron mobility of LEC undoped SI-GaAs crystals

Z.G. Wang Ye Jing Dai C.J. Li H.P. Lu Zhen Deng

LEC undoped SI-GaAs materials obtained from different sources have been systematically investigated by using various techniques such as Hall effect measurements, IR absorption and Photoluminescence Mapping etc.. A strong dependence of electron mobility on spatial distribution of impurities and defects across the wafers revealed by spatially resolved photoluminescence at R.T. are observed. Spam-charge region scattering resulted from nominiformity is induced in theoretically calculating the electron mobility. A semi-empirical formula is presented by least-square fitting the mobility data obtained from temperature dependent Hall measurements. Additionally, the density and the scattering cross section of space-charge region and ionized impurity concentration were obtained.

Electron Mobility

Ionized impurity scattering

10.1109/sim.1992.752712

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Nonblinking Colloidal Quantum Dots via Efficient Multiexciton Emission

The Journal of Physical Chemistry Letters (2022)

Mingcai Xie Chen‐Lei Tao Zhen Zhang Hanyu Liu Sushu Wan

Nonblinking colloidal quantum dots (QDs) are significant to their applications as single-photon sources or light-emitting materials. Herein, a simple heat-up method was developed to synthesize high-qualityWZ-CdSe/CdS core-shell colloidal QDs, which achieved a near-unity photoluminescence quantum yield (PLQY). It was found that the blinking behavior of such QDs was completely suppressed at high excitation intensities, and ultra-stable PL emission was observed. For this reason, a systematic investigation was conducted, revealing that the complete blinking suppression was attributed mainly to the efficient multiexciton emission at high excitation intensities. Such high-quality QDs with nonblinking behaviors and nearly ideal PL properties at high excitation intensities have massive potential applications in various robust conditions, including QD display screens, single-particle tracks, and single-photon sources.

Quantum yield

10.1021/acs.jpclett.2c00378

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Citations (6)

Red-Shifted Photoluminescence from Crystal Edges Due to Carrier Redistribution and Reabsorption in Lead Triiodide Perovskites

The Journal of Physical Chemistry (2019)

Daocheng Hong Jun Li Sushu Wan Ivan G. Scheblykin Yuxi Tian

Photoluminescence (PL) of CH₃NH₃PbI₃ perovskites depends strongly on sample preparation, atmosphere, crystal size, and so forth. However, the origin of these dependencies is always misunderstood because of the co-works of many different factors. Herein, we prepared hexagonal-shaped single crystals with tens of micrometers in size and observed a red-shifted PL emission (800–830 nm) mainly from the crystal edges besides the usual band-to-band transition (760 nm) from the central regions. Also, significantly different time-resolved dynamics and excitation power dependencies were observed. To summarize, we conclude that the red-shifted component comes from the depth of the crystal, where monomolecular recombination occurs involving photogenerated charges and unintentional doped charges, while the normal PL is emitted by bimolecular recombination from the surface layers. These results showed the significance of pure optical effects in perovskite crystals and would promote detailed understanding of the charge dynamics and recombination in perovskite crystalline materials of different geometries and sizes.

Triiodide

Crystal (programming language)

Redistribution

Charge carrier

Source

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Elimination of unexpected destruction on CsPbBrxI3-x nanocrystals arising from polymer matrix

Journal of Luminescence (2022)

Yajie Zhu Daocheng Hong Yan Nie Hanyu Liu Sushu Wan

Backlight

Matrix (chemical analysis)

Quantum Efficiency

10.1016/j.jlumin.2022.119147

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Citations (3)

Steric Engineering Enables Efficient and Photostable Wide‐Bandgap Perovskites for All‐Perovskite Tandem Solar Cells

Advanced Materials (2022)

Jin Wen Yicheng Zhao Zhou Liu Han Gao Renxing Lin

Wide-bandgap (WBG, ≈1.8 eV) perovskite is a crucial component to pair with narrow-bandgap perovskite in low-cost monolithic all-perovskite tandem solar cells. However, the stability and efficiency of WBG perovskite solar cells (PSCs) are constrained by the light-induced halide segregation and by the large photovoltage deficit. Here, a steric engineering to obtain high-quality and photostable WBG perovskites (≈1.8 eV) suitable for all-perovskite tandems is reported. By alloying dimethylammonium and chloride into the mixed-cation mixed-halide perovskites, wide bandgaps are obtained with much lower bromide contents while the lattice strain and trap densities are simultaneously minimized. The WBG PSCs exhibit considerably improved performance and photostability, retaining >90% of their initial efficiencies after 1000 h of operation at maximum power point. With the triple-cation/triple-halide WBG perovskites enabled by steric engineering, a stabilized power conversion efficiency of 26.0% in all-perovskite tandem solar cells is further obtained. The strategy provides an avenue to fabricate efficient and stable WBG subcells for multijunction photovoltaic devices.

Tandem

10.1002/adma.202110356

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Citations (101)

Photo-induced dual passivation via Usanovich acid–base on surface defects of methylammonium lead triiodide perovskite

Physical Chemistry Chemical Physics (2018)

Yue Yu Sushu Wan Daocheng Hong Yuxi Tian

Post-fabrication defect passivation of organometal halide perovskites has become an efficient way to improve their photophysical properties, but the underlying mechanisms are still in debate. In this work, we used p-benzoquinone (p-BQ) to generate surface defects on methylammonium lead triiodide perovskite (MAPbI3), and found that a Usanovich acid-base (O2, acetone or acetonitrile) treatment can effectively passivate those defects and lead to photoluminescence (PL) enhancement. The passivation effect arose from partial neutralization of defect charges via electron transfer between passivation reagents and relevant defects. O2 accepted photo-generated electrons, formed negatively charged oxygen species and attached to the I vacancy site to reduce its PL quenching efficiency by neutralising the defects positive charge. Likewise, acetone accepted photo-generated holes, formed positively charged species and partially neutralised the defects negative charge. The reduced trapping ability of defects caused PL enhancement. In addition, the observed photo-catalysed oxidation of acetone by O2 on the crystal surface supported the single electron transfer mechanism, and showed the potential of MAPbI3 as a photo-catalyst.

Passivation

Triiodide

10.1039/c8cp06112b

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Citations (6)

Physical insights into protection effect of conjugated polymers by natural antioxidants

RSC Advances (2021)

Mingcai Xie Hua Yan Daocheng Hong Sushu Wan Yuxi Tian

Conjugated polymers (CPs) known as organic semiconductors have been broadly applied in photovoltaic and light emitting devices due to their easy fabrication and flexibility. However, one of the bottlenecks limiting the application of CPs is their poor photostability upon continuous excitation which is one of the crucial parameters of CPs. How to improve the photostability of CPs is always one of the key questions in this field. In this work, we found that the photostability of poly(3-hexylthiophene-2,5-diyl) (P3HT) molecules can be largely improved by addition of vitamin E (VE) in bulk solution, solid films and single molecules. In solution and films, VE can not only significantly retard the photodegradation of P3HT but also enhance the fluorescence intensity. For individual P3HT molecules, with increasing VE concentrations, the on-time duration increases and the off-time duration becomes shorter. VE as natural antioxidants can not only donate electrons to the long-lived charged species but also quench the triplet states of CPs via energy transfer accelerating the depopulation process back to the ground state. The short duration time of the charged species and the triplet states provides higher fluorescence intensity. Furthermore, VE can also directly react with singlet oxygen or other reactive oxygen species (ROS) preventing them from reacting with CPs. These results not only provide an efficient strategy for improving the photostability of conjugated polymers in solution and films, but also shed light on better understanding the photophysics of conjugated polymers at single-molecule level.

Photodegradation

10.1039/d0ra09657a

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Citations (1)

Rapid determination of all element in MAPbI3 thin films using laser induced breakdown spectroscopy

Spectrochimica Acta Part B Atomic Spectroscopy (2021)

Xianshuang Wang Sushu Wan Yage He Suling Qiu Xiao Ma

Laser-induced breakdown spectroscopy

Stoichiometry

Laser Ablation

Photoelectric effect

10.1016/j.sab.2021.106123

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Citations (12)

Controllable Introduction of Surface Defects on CH3NH3PbI3 Perovskite

Nanomaterials (2022)

Sushu Wan Yajie Zhu Daocheng Hong Yuxi Tian

One of the unique characteristics of semiconductors is the strong dependence of their properties on crystal defects and doping. However, due to the species diversity and low density, it is very difficult to control the type and concentration of the defects. In perovskite materials, crystal defects are randomly formed during the fast crystallization process, causing large heterogeneity of the samples. Here, in this work, we report a controllable method to introduce surface defects on CH3NH3PbI3 perovskite materials via the interaction with 1,4-benzoquinone (BQ) molecules on the gas and solid interface. After the adsorption of BQ molecules on the perovskite surface, surface defects can be generated by photoinduced chemical reactions. The concentration of the defects can thus be controlled by precisely regulating the laser irradiation time. The concentration of the defects can be characterized by a gradually decreased PL intensity and lifetime and was found to influence the atmospheric response and the subsequent acetone-induced degradation of the materials. These results demonstrate that crystal defects in perovskite materials can be controllably introduced, which provides a possible way to fully understand the correlation between the nature and chemical structure of these defects.

Crystal (programming language)

10.3390/nano12061002

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Citations (1)