Mechanism suppressing charge recombination at iodine defects in CH3NH3PbI3 by polaron formation

Metal-halide perovskites exhibit high efficiencies in photovoltaic applications and low recombination rates, despite the high concentrations of intrinsic defects. We here study the hole trapping at the negative iodine interstitial, which corresponds to the dominating recombination center in CH3NH3PbI3. We calculate the free energy profile for the hole trapping at 300 K using the Blue Moon technique based on hybrid functional molecular dynamics. We find that the hole trapping is energetically unfavorable and requires overcoming an energy barrier. This behavior stems from the position of the vertical (-/0) transition level of the iodine defect and the formation of a polaron. Our simulations show that the polaron does not interact with the iodine interstitial and hops through the lattice on a sub-picosecond scale. Our results highlight a mechanism by which the low mononuclear (trap-assisted) recombination rates in CH3NH3PbI3 can be explained.


Published in:
Journal Of Materials Chemistry A, 6, 35, 16863-16867
Year:
Sep 21 2018
Publisher:
Cambridge, ROYAL SOC CHEMISTRY
ISSN:
2050-7488
2050-7496
Keywords:
Laboratories:




 Record created 2018-12-13, last modified 2019-06-19


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