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Highlight Lecture

WEB Femto- to Microsecond Dynamics of Excited Electrons in a Quadruple Cation Perovskite

Wednesday (23.09.2020)
15:15 - 15:30 F: Functional Materials, Surfaces, and Devices 1
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The efficiency of perovskite solar cells based on the ABX3 structure (A = e.g. Cs, CH3NH3, B = Pb, X = I, Br, Cl) has skyrocketed (25.2%) among the solution processed PV technologies, their innovation consists primarily in processability from solution and mild temperatures. Combining different organic and inorganic cations on the A-site and mixing halides on the X-site, could lead to highly efficient and stabilized hybrid perovskites. In this work, guanidinium containing 3D quadruple cation mixed halide perovskite single crystals were grown using an inverse temperature crystallization process. Complementary time-resolved spectroscopy confirmed that polycrystalline thin films and single crystals identically composed exhibit similar carrier dynamics in the picosecond range. Cooling of excited carriers and bandgap renormalization occur on the same time scale of 200–300 fs. At low excitation density, a long carrier lifetime of 3.2 μs was recorded possibly due to the passivation of recombination centers. This study clarifies discrepancies about the lifetime of hot carriers, the impact of radiative recombination, and the role of recombination centers on solar cell performance. The quadruple cation perovskites displayed short time dynamics with slow recombination of charge carriers leading to power conversion efficiencies above 20%.

Speaker:
Feray Ünlü
University of Cologne
Additional Authors:
  • Eunhwan Jung
    University of Cologne
  • Kestutis Budzinauskas
    University of Cologne
  • Dr. Senol Öz
    University of Cologne
  • Prof. Dr. Paul H. M. van Loosdrecht
    University of Cologne
  • Prof. Dr. Luca Perfetti
    Ecole Polytechnique
  • Prof. Dr. Sanjay Mathur
    University of Cologne