Nature of charge capture at the iodine interstitial site. Interstitial is metastable but has been suggested to form under illumination, 24, 25 which is our focus here. In a p-type regime (E F close to the valenceīand) and the negative charge is favored in an n-type regime (E F close to the conduction band). In the dark, the positive charge state is thermodynamically favored With the longest I–I bond length of all three charge states. Orbitals are filled, resulting in a split-interstitial configuration 23 In the negative charge state, the antibonding

With the longer bond possessing the majority of the additional charge. In CsI 3 has interbond distances of 2.82 and 3.10 Å, Positive charge state, an asymmetric trimer structure isįound that is typical of I 3 –. The octahedral tilting pattern, we distinguish between in-plane (IP)Īnd out-of-plane (OP) configurations for this defect. 22 Our bond lengths are within 0.05 Å of this value. Which lengthens to 3.23 Å upon formation of I 2 –. The I–Iīond length in solid orthorhombic crystalline iodine is 2.67 Å, With bond lengths that are sensitive to the charge state. 21 Iodine is well-known to form polyiodide chains Paramagnetic S = (1/2) spin configuration. To as an H-center by the metal halide community and has a characteristic Iodine atom in an interstitial region, bonds with a lattice iodine Is colored in purple, and the lead, in gray. IP indicates that the neutralĭefect is lying in the ab-plane. Supercell built from an expansion of the 12-atom unit cell, usingĭefect geometries of I i +, I i –, I i IP, and The interstitial was placed in a 192-atom

Octahedral tilts the starting point for atomic relaxation was MAPI So that no preference was given to a particular With an accuracy of 0.02 meV per atom, and a 2 × 2 × 2 gammaĬentered Monkhorst–Pack mesh was used for the Brillouin zone Projection operators were optimized in real space (DFT) as implemented in the GPU port of VASP, 16 using a plane wave basis set with an energyĬutoff of 400 eV. This builds on the approach of Alkauskas et al., 12 and the implementation has been applied to aĮlectronic structures were calculated using density functional theory 13 The 1D SchrödingerĮquation for the potential energy surface was solved using a finiteĭifference method. Of electron capture was performed using the open-source CarrierCapture package. Taking the example of a neutral defect (D 0), the

The excess electronic energy of the charge carriers is lost Through the associated structural relaxation, 11 as illustrated in Figure Figure1 1.

A necessary step is the change from delocalized-to-localizedĮlectronic wave functions, and multiple phonon (ℏω) emission To first-order in a heavily doped ( n or p type) semiconductor minority carrier capture becomes the rate-limiting With the successive capture of an electron and hole following the The iodine interstitial in CH 3NH 3PbI 3 (MAPI). 10 In this report, we perform a quantum mechanicalĬarrier-capture analysis of the interaction between electrons and Of nonradiative carrier capture and recombination events. In the performance of halide perovskite devices requires suppression This behavior of halide perovskites has beenīroadly termed “defect tolerance”. Processing introduces additional disorder, 6 the native defects do not appear to contribute to nonradiative recombination Populations are expected based on equilibrium thermodynamics 5 of these soft crystalline materials, and solution Supports high voltage and efficient light-to-electricity conversion Recombination is unusual for solution processed semiconductors and Chemistry and physics of lead halide perovskites

Electron capture formula