Unravelling the effects of oxidation state of interstitial iodine and oxygen passivation on charge trapping and recombination in CH₃NH₃PbI₃ perovskite: a time-domain ab initio study

Abstract

The oxidation state of interstitial iodine and oxygen passivation control the electron–hole recombination in CH3NH3PbI3 perovskite.

Extending Carrier Lifetimes in Lead Halide Perovskites with Alkali Metals by Passivating and Eliminating Halide Interstitial Defects

“…[12,17,20] Quantum dynamics simulations show that elimination of the mid-gap trap state by oxidation of I i to I i À prolongs carrier lifetimes. [18] Unfortunately,I i À is unstable under light illumination, [17b] since the negative interstitial iodine can readily trap ahole to transform to the neutral iodine interstitial, lowering perovskite device performance. [17c] De Angelis and co-authors have explored more iodine oxidation states in order to elucidate whether the nonradiative energy losses can be reduced.…”

Extending Carrier Lifetimes in Lead Halide Perovskites with Alkali Metals by Passivating and Eliminating Halide Interstitial Defects

“…Theory indicates that adjusting the oxidation state of the interstitial iodine can control carrier dynamics and reduce nonradiative carrier recombination . Quantum dynamics simulations show that elimination of the mid‐gap trap state by oxidation of I i to I i − prolongs carrier lifetimes . Unfortunately, I i − is unstable under light illumination, since the negative interstitial iodine can readily trap a hole to transform to the neutral iodine interstitial, lowering perovskite device performance .…”

The Interplay Between Lead Vacancy and Water Rationalizes the Puzzle of Charge Carrier Lifetimes in CH3NH3PbI3: Time‐Domain Ab Initio Analysis

“…The two iodine atoms formed iodine dimer are highlighted by the cyan spheres in the right‐hand‐side panel of Figure c. The iodine dimer remains stable during the MD simulation with a slightly increased distance of 2.818 Å. In general, iodine dimerization tends of form an electron trap state and accelerates charge recombination . In contrast, two additional electrons repulse with the iodine anions and thus break the iodine dimer in the V Pb −2 _H 2 O system, expanding the I−I distance to 4.072 at 0 K and 4.433 Å at 300 K, shown in the right‐hand‐side panel of Figure d. Therefore, one expects that the formation and breaking of the iodine dimer in the two structures significantly affect their electronic structures and excited‐state dynamics.…”

“…While which increases significantly to 3.215 and 3.212 in the V Pb _H 2 Oa nd V Pb À2 _H 2 Os ystems by 0.051 and 0.049 , respectively.I ndeed, thermal motions drive as ignificant elongation of Pb À Ib ond length in MAPbI 3 in the presence of both water molecules and lead vacancy.Importantly,water molecules enable the two neighboring iodine atoms around the lead vacancy attracting each other in the V Pb _H 2 Osystem, leading to formation of an iodine dimer with aI À Idistance of 2.740 .T he two iodine atoms formed iodine dimer are highlighted by the cyan spheres in the right-hand-side panel of Figure 2c.T he iodine dimer remains stable during the MD simulation with as lightly increased distance of 2.818 .I n general, iodine dimerization tends of form an electron trap state and accelerates charge recombination. [25] In contrast, two additional electrons repulse with the iodine anions and thus break the iodine dimer in the V Pb À2 _H 2 Os ystem, expanding the I À Id istance to 4.072 at 0K and 4.433 at 300 K, shown in the right-hand-side panel of Figure 2d. Therefore,one expects that the formation and breaking of the iodine dimer in the two structures significantly affect their electronic structures and excited-state dynamics.…”