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Impact of Organic Spacers on the Carrier Dynamics in 2D Hybrid Lead-Halide Perovskites
摘要： We have carried out non-adiabatic molecular dynamics simulations combined with time-dependent density functional theory calculations to compare the properties of the two-dimensional (2D) (BA)2(MA)Pb2I7 and three-dimensional (3D) MAPbI3 (where MA = methylammonium and BA = butylammonium) materials. We evaluate the different impacts that the 2D-confined spacer layer of butylammonium cations and the 3D-confined methylammonium cations have on the charge carrier dynamics in the two systems. Our results indicate that while both the MA+ and BA+ cations play important roles in determining the carrier dynamics, the BA+ cations exhibit stronger non-adiabatic couplings with the 2D perovskite framework. The consequence is a faster hot-carrier decay rate in 2D (BA)2(MA)Pb2I7 than in 3D MAPbI3. Thus, tuning of the functional groups of the organic spacer cations in order to reduce the vibronic couplings between the cations and the Pb-I framework can offer the opportunity to slow down the hot-carrier relaxations and increase the carrier lifetimes in 2D lead-halide perovskites.
关键词： carrier dynamics,2D hybrid lead-halide perovskites,time-dependent density functional theory,non-adiabatic molecular dynamics,organic spacers
更新于2025-09-23 15:21:21
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Control of Charge Carrier Dynamics in Plasmonic Au Films by TiO <sub/><i>x</i> </sub> Substrate Stoichiometry
摘要： Plasmonic excitations in noble metals have many fascinating properties and give rise to a broad range of applications. We demonstrate, using non-adiabatic molecular dynamics combined with time-domain density functional theory, that chemical composition and stoichiometry of substrates can have a strong influence on charge dynamics. By changing oxygen content in TiO2, including stoichiometric, oxygen rich and oxygen poor phases, and Ti metal, one can alter lifetimes of charge carriers in Au by a factor of 5, and control the ratio of electron-to-hole relaxation rates by a factor of 10. Remarkably, a thin TiOx substrate alters so much charge carrier properties in much thicker Au films. Such large variations stem from the fact that the Ti and O atoms are much lighter than Au, and their vibrations are much faster at dissipating the energy. The control over a particular charge carrier and an energy range depends on the Au and TiOx level alignment, and the interfacial interaction strength. These factors are easily influenced by the TiOx stoichiometry. In particular, oxygen rich and poor TiO2 can be used to control holes and electrons, respectively, while metallic Ti affects both charge carriers. The detailed atomistic analysis of the interfacial and electron-vibrational interactions generates the fundamental understanding of the properties of plasmonic materials needed to design photovoltaic, photocatalytic, optoelectronic, sensing, nanomedical and other devices.
关键词： non-adiabatic molecular dynamics,substrate layers,time-domain density functional theory,metallic films,electron-phonon energy relaxation,surface plasmons
更新于2025-09-19 17:13:59