Communication: Non-radiative recombination via conical intersection at a semiconductor defect

Shu, Yinan; Levine, Bernard B.

doi:10.1063/1.4819784

Cited by 24 publications

(34 citation statements)

References 48 publications

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“…AIMS coupled to GPUaccelerated SA-CASSCF reproduced the experimentally observed biexponential decay of photoexcited provitamin-D 3 , a molecule with 51 atoms. 185 The experimental timescales were also reproduced and the calculations indicated (in contradiction to previous 324 [314][315] AIMS/SA-CASSCF nonadiabatic dynamics identified fast relaxation mediated by conical intersections between S 1 and S 0 (see Figure 15 for Si 8 H 12 O), hence proposing recombination pathways in the presence of epoxides. Importantly, reaching the conical intersection implies a photochemical ring-opening mechanism, whose mechanism slightly differs between the studied clusters.…”

Section: Ab Initio Multiple Spawningmentioning

confidence: 54%

Ab Initio Nonadiabatic Quantum Molecular Dynamics

2018

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The Born-Oppenheimer approximation underlies much of chemical simulation and provides the framework defining the potential energy surfaces that are used for much of our pictorial understanding of chemical phenomena. However, this approximation breaks down when the dynamics of molecules in excited electronic states are considered. Describing dynamics when the Born-Oppenheimer approximation breaks down requires a quantum mechanical description of the nuclei. Chemical reaction dynamics on excited electronic states is critical for many applications in renewable energy, chemical synthesis, and bioimaging. Furthermore, it is necessary in order to connect with many ultrafast pump-probe spectroscopic experiments. In this review, we provide an overview of methods that can describe nonadiabatic dynamics, with emphasis on those that are able to simultaneously address the quantum mechanics of both electrons and nuclei. Such ab initio quantum molecular dynamics methods solve the electronic Schrödinger equation alongside the nuclear dynamics and thereby avoid the need for precalculation of potential energy surfaces and nonadiabatic coupling matrix elements. Two main families of methods are commonly employed to simulate nonadiabatic dynamics in molecules: full quantum dynamics, such as the multiconfigurational time-dependent Hartree method, and classical trajectory-based approaches, such as trajectory surface hopping. In this review, we describe a third class of methods that is intermediate between the two: Gaussian basis set expansions built around trajectories.

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Section: Ab Initio Multiple Spawningmentioning

confidence: 54%

Ab Initio Nonadiabatic Quantum Molecular Dynamics

2018

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“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 20 Lastly, it is worth discussing similarities and difference between the 3O and 5O defects studied here and the 1O epoxide defect we have previously investigated. 37 All three defects decay via a conical intersection which is accessed after a photochemical ring opening reaction.…”

Section: Disucussionmentioning

confidence: 99%

Nonradiative Recombination via Conical Intersections Arising at Defects on the Oxidized Silicon Surface

Shu

Levine

2015

J. Phys. Chem. C

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Non-radiative recombination of excitations in semiconductors limits the performance of photovoltaics, light-emitting diodes, photocatalysts, and other devices. Herein we investigate the role that two known defects on the oxidized surface of silicon play in non-radiative recombination in silicon nanocrystals. We apply ab initio multiple spawning and multireference electronic structure methods to model the non-radiative processes which follow excitation of two cluster models of silicon epoxide defects that differ in the oxidation state of their respective silicon atoms. We find conical intersections in both clusters, and these intersections are found to be accessible at energies corresponding to visible wavelengths. In both cases photochemical opening of the epoxide ring precedes non-radiative decay. These results support the hypothesis that conical intersections associated with specific defect structures on the oxidized surface of silicon nanocrystals facilitate non-radiative recombination. Discussion regarding how this hypothesis can be tested experimentally is presented. Keywordscomplete active space self-consistent field (CASSCF), semiconductor nanoparticle, quantum dot,

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“…46 In this work, we used ab initio calculations to investigate the electronic properties and charge recombination dynamics in oxidized Si NPs containing surface DBs. We focused on the relative probability of radiative and nonradiative recombination processes [47][48][49][50] as a function of stress at or close to the surface of the NP, where defects are present. From our results, we predicted that surface DBs introduce defect states which can cause blinking within oxidized Si NPs, and these DB states are responsible for the exponential blinking statistics observed experimentally in Si NP/oxide composites.…”

Section: Introductionmentioning

confidence: 99%

Surface dangling bonds are a cause of B-type blinking in Si nanoparticles

2015

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Exponential blinking statistics was reported in oxidized Si nanoparticles and the switching mechanism was attributed to the activation and deactivation of unidentified nonradiative recombination centers. Using ab initio calculations we predicted that Si dangling bonds at the surface of oxidized nanoparticles introduce defect states which, depending on their charge and local stress conditions, may give rise to ON and OFF states responsible for exponential blinking statistics. Our results are based on first principles calculations of charge transition levels, single particle energies, and radiative and nonradiative lifetimes of dangling bond defects at the surface of oxidized silicon nanoparticles under stress.

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Communication: Non-radiative recombination via conical intersection at a semiconductor defect

Cited by 24 publications

References 48 publications

Ab Initio Nonadiabatic Quantum Molecular Dynamics

Ab Initio Nonadiabatic Quantum Molecular Dynamics

Nonradiative Recombination via Conical Intersections Arising at Defects on the Oxidized Silicon Surface

Surface dangling bonds are a cause of B-type blinking in Si nanoparticles

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