Research_fane

Research

Photo-chemical/physical study of hybrid perovskite nanoparticles.:
This project focuses on the structures and excited state dynamics of lead halide perovskite nanoparticles (MAPbX3and CsPbX3). Such materials are derived from their famous bulk counterparts for photovoltaic application. However it exhibit entirely different optical properties such as high emission quantum yield, long-term photostability, large multi-photon absorption cross-section. The main objective is to reveal the photophysical origins of such properties in perovskite nanoparticles, which is implemented through two direction. The first direction is to reveal the electronic structures of such nanoparticles using X-ray based technics (e.g. XRD, XPSand XAS) conducted in synchrotron facilities. With the help of such characterization, clear overview on the ground state nature would be constructed. The second direction focuses on the excited state dynamics studied by time-resolved laser spectroscopies such as transient absorption and time-resolved photoluminescence spectroscopy. We have verified the major origin of the enhanced emission from Wannier-Mottexcitons which results from the enhanced exciton binding energy induced by lattice distortion in nanoparticles. In addition, the effectof surface trap states inperovskite nanoparticles is minimized through 1) self-healing of the trap states and 2) passivation from the surface ligands.

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Representative Papers:

  1. J. Chen, M. E. Messing, K. B. Zheng, T. Pullerits, “Cation Dependent Hot Carrier Cooling in Halide Perovskite Nanocrystals”, J. Am. Chem. Soc. 141(2019)3532-3540.
  2. J. Chen, K. Zidek, P. Chábera, D. Liu, P. Cheng, L. Nuuttila, M. J. Al-Marri, H.i Lehtivuori, M. E Messing, K. Han, K. B. Zheng*, T. Pullerits*, “Size-and wavelength-dependent two-photon absorption cross-section of CsPbBr3 perovskite quantum dots”, Journal of Physical Chemistry Letters, 10(2017)2316-2321.
  3. K. B. Zheng*, K. Zidek, M. Abdellah, J. Cheng, P. Chabera, W. Zhang, M. J. Al-Marri, T. Pullerits*, “High Excitation Intensity Opens a New Trapping Channel in Organic-inorganic Hybrid Perovskite Nanoparticles” ACS Energy Letters, 1(2016) 1154-1161.
  4. K. B. Zheng, Q. Zhu, M. Abdellah, M. E. Messing, W. Zhang, A. Generalov, Y. Niu, L. Ribaud, S. E. Canton, T. Pullerits, “Exciton Binding Energy and the Nature of Emissive States in Organometal Halide Perovskites”, Journal of Physical Chemistry Letters, 6(2015)2969-2975
Structure and its photo-induced dynamics in photoactive nanomaterials.In this project, I utilize time-resolved X-ray absorption and scattering spectroscopy to study the photo-induced transient structural change in perovskite material. Specially the formation of strong-coupling polarons and consequently lattice distortions. Such behavior has been theoretically predicted as the critical factor dominating the charge carrier mobility of organo-metal perovskites. By monitoring the evolution of the local structure at time scale of picoseconds and after excitation, we managed to obtain experimental evidence for the hypothesis. The current work is to systematical profile structural dynamics and interpret it with proper model while probe the polaron formation dynamics at even early timescale using XFEL technics in EU-XFEL as well as SCALA, Japan. This project is mainly cooperated with Dr. Sophie Canton in Eli-Alps Institute, Hungry.
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    Related Papers:

    1. C. Liu, Y. Wang, H. Geng, T. Zhu, E. Ertekin, D. Gosztola, S. Yang, J. Huang, B. Yang, K. Han, S. Canton, Q. Kong, K. B. Zheng*, X. Zhang*, , “Asynchronous photoexcited electronic and structural relaxation in lead-free perovskites”, J. Am. Chem. Soc., 141(2019)13074-13080.
    2. K. B. Zheng, M. Abdellah, Q. Zhu, Q. Kong, G. Jenning, CA Kurtz, M. E. Messing, Y. Niu, D. J. Gosztola, M. J. Al-Marri, X. Zhang, T. Pullerits, S. E. Canton “Direct Experimental Evidence for Photoinduced Strong-Coupling Polarons in Organolead Halide Perovskite Nanoparticles”, Journal of Physical Chemistry Letters, 7(2016)4535-4539
    3. M. Abdellah, F. Poulsen, Q. Zhu, N. Zhu, K. Zidek, P. Chabera, A. Corti, T. Hansen, Q. Chi, S. E. Canton, K. B. Zheng*, T. Pullerits*, “Drastic difference between hole and electron injection through the gradient shell of CdxSeyZn1-xS1-y quantum dots”, Nanoscale, 34(2017)12503-12508.

     

      Development of two-dimensional halide perovskite structures and device application.:Traditional organo-metal halide perovskite achieving 22.1% solar cell efficiency still suffer from the instability towards atmosphere specially moisture, which becomes the bottleneck for the industrialization. Partially replacement of short chain organic cation in the perovskite octahedra with hydrophobic long chain ligands to build up so called 2D perovskite structures has been proved to effective enhance the moisture resistance of the perovskites. However, it sacrifices the crystalline uniformity and surplus charge carrier transportation. In this scenario, tailoring the material structure with balance between high stability and efficient charge collection efficiency is highly demanded in the community, which is the main target of the project. Cooperated with solar cell device group lead by Prof. Ziqi Lang in China, we work on the engineering of the composition, geometry, and stoichemistry of the 2D perovskites through charge carrier dynamics analysis. paper_3

      Related Papers:

      1. M. Liang, W. Lin, Z. Lan, J. Meng, Q. Zhao, X. Zou, I. E. Castelli, T. Pullerits, S. E. Canton*, K. B. Zheng*, “Electronic Structure and Trap-States of Two-Dimensional Ruddlesden-Popper Perovskites with Relaxed Goldschmidt Tolerance Factor”, ACS Applied Electrical Materials, 2020, accepted.
      2. K. B. Zheng*, T. Pullerits*, “Two dimensions are better for perovskites”, J. Phys. Chem. Lett., 10(2019)5881-5885.
      3. Y. Yan, S. Yu, A. Honarfar, T. Pullerits, K. B. Zheng*, Z. Liang*, “Benefiting from Spontaneously Generated 2D/3D Bulk‐Heterojunctions in Ruddlesden− Popper Perovskite by Incorporation of S‐Bearing Spacer Cation”, Adv. Sci. (2019): doi.org/10.1002/advs.201900548.
      4. K. B. Zheng*, Y. Chen, Y. Sun, J. Chen, P. Chabera, R. Schaller, M. J. Al-Marri, S. E. Canton, Z. Liang, T. Pullerits*, “Inter-phase charge and energy transfer in Ruddlesden–Popper 2D perovskites: critical role of the spacing cations”, J Mater. Chem. A, 15(2018)6244-6250.
      5. J. Peng, Y. Chen, K. Zheng*, T. Pullerits, Z. Liang*. Insights into charge carrier dynamics in organo-metal halide perovskites: from neat films to solar cells. Chem. Soc. Rev. 46(2017)5714-5729.
      6. Y. Chen, Y. Sun, J. Peng, W. Zhang, X. Su, K. B. Zheng, T. Pullerits, Z. Liang, “Tailoring Organic Cation of Two-Dimensional Air-Stable Organometal Halide Perovskites for Highly Efficient Planar Solar Cells”, Advanced Energy Materials, 7(2017)1700162
      Transition metal doping in colloidal quantum dots.:The emerging transition metal ion (e.g. Mn2+and Co2+, etc.) doping in QDs provided new opportunities for their application in optoelectronic devices. The doping states usually exhibit longer lifetime and larger DOS which can facilitate the charge separation in the device. Moreover, their ferromagnetic feature opens up an extra tool to modulate the photo-physical properties by spin polarization. In this project, the correlation between doping level and the photo-physics is revealed by the ultrafast spectroscopy. paper_4

      Related paper:

      1. J. Meng, Z. Lan, M. Abdellah, B. Yang, S. Mossin, M. Liang, M. Naumova, Q. Shi, S. Alvarez, Y. Liu, W. Lin, I. E. Castelli, S. E. Canton, T. Pullerits, K. B. Zheng*, “Modulating Charge Carrier Dynamics in Mn-Doped All-inorganic Halide Perovskite Quantum Dots through the Doping-Induced Deep Trap States”, J. Phys. Chem. Lett., 2020, accepted.
      Updated on 21 September 2020
      Updated on 21 September 2020