اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدPhotoexcited organic molecules $en~route$ to highly efficient autoionization
71
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The conversion of optical and electrical energy in novel materials is key to modern optoelectronic and light-harvesting applications. Here, we investigate the equilibration dynamics of photoexcited 2,7-bis(biphenyl-4-yl)-2,7-ditertbutyl-9,9-spirobiuorene (SP6) molecules adsorbed on ZnO(10-10) using femtosecond time-resolved two-photon photoelectron (2PPE) and optical spectroscopy. We find that, after initial ultrafast relaxation on fs and ps timescales, an optically dark state is populated, likely the SP6 triplet (T) state, that undergoes Dexter-type energy transfer ($r_{mathrm{Dex}} = 1.3~mathrm{nm}$) and exhibits a long decay time of 0.1 s. Because of this long lifetime a photostationary state with average T-T distances below 2 nm is established at excitation densities in the $10^{20}~mathrm{cm}^{-2}~mathrm{s}^{-1}$ range. This large density enables decay by T-T annihilation (TTA) mediating autoionization despite an extremely low TTA rate of $k_{mathrm{TTA}} = 4.5~10^{-26}~mathrm{m}^3~mathrm{s}^{-1}$. The large external quantum efficiency of the autoionization process (up to 15 %) and photocurrent densities in the mathrm{mA}~mathrm{cm}^{-2}$ range offer great potential for light-harvesting applications.
قيم البحث
اقرأ أيضاً
Employing a rigorous theoretical method for the construction of exact many-electron ground states we prove that interactions can be employed to tune a bare dispersive band structure such that it develops a flat band. Thereby we show that pentagon cha
in polymers with electron densities above half filling may be designed to become ferromagnetic or half metallic.
Recently, a host/guest clathrate SrB3C3 with sp3-bonded boron-carbon framework was synthesized at around 50 GPa. On the basis of electron count, the structure is understood as guest Sr2+ cations intercalated in the (B3C3)3- framework. Previous calcul
ations suggest that SrB3C3 is a hole conductor with an estimated superconducting critical temperature (Tc) of 42 K at ambient pressure. If atoms with similar radius, such as Rb, can substitute Sr2+ in the lattice, the electronic as well as superconductivity properties of this material will be modified significantly. Here, we perform extensive simulations on the stability and physical properties of Rb-Sr-B3C3 system using first-principles density functional calculation in combination with cluster expansion and CALYPSO structure prediction method. We predict a phonon-mediated superconductor Rb0.5Sr0.5B3C3 with a remarkably high Tc of 78 K at ambient pressure, which is a significant improvement from the estimated value (42 K) in SrB3C3. The current results suggest that substitution of alkali atom in synthesized clathrate SrB3C3 is a viable route toward high-Tc compounds.
The chemical potentials of multicomponent fluids are derived in terms of the pair correlation functions for arbitrary number of components, interaction potentials, and dimensionality. The formally exact result is particularized to hard-sphere mixture
s with zero or positive nonadditivity. As a simple application, the chemical potentials of three-dimensional additive hard-sphere mixtures are derived from the Percus-Yevick theory and the associated equation of state is obtained. This Percus-Yevick chemical-route equation of state is shown to be more accurate than the virial equation of state. An interpolation between the chemical-potential and compressibility routes exhibits a better performance than the well-known Boublik-Mansoori-Carnahan-Starling-Leland equation of state.
In hybrid lead halide perovskites, the coupling between photogenerated charges and the ionic degrees of freedom plays a crucial role in defining the intrinsic limit of carrier mobility and lifetime. However, direct investigation of this fundamental i
nteraction remains challenging because its relevant dynamics occur on ultrashort spatial and ultrafast temporal scales. Here, we unveil the coupled electron-lattice dynamics of a CH3NH3PbI3 single crystal upon intense photoexcitation through a unique combination of ultrafast electron diffraction, time-resolved photoelectron spectroscopy, and time-dependent ab initio calculations. We observe the structural signature of a hot-phonon bottleneck effect that prevents rapid carrier relaxation, and we uncover a phonon avalanche mechanism responsible for breaking the bottleneck. The avalanche involves a collective emission of low-energy phonons - mainly associated with the organic sub-lattice - that proceeds in a regenerative manner and correlates with the accumulation and confinement of photocarriers at the crystal surface. Our results indicate that in hybrid perovskites carrier transport and spatial confinement are key to controlling the electron-phonon interaction and their rational engineering is relevant for future applications in optoelectronic devices.
Spacecraft investigations during the last ten years have vastly improved our knowledge about dust in the Jovian system. All Galilean satellites, and probably all smaller satellites as well, are sources of dust in the Jovian system. In-situ measuremen
ts with the dust detectors on board the Ulysses and Galileo spacecraft have for the first time demonstrated the electromagnetic interaction of charged dust grains with the interplanetary magnetic field and with a planetary magnetosphere. Jupiters magnetosphere acts as a giant mass-velocity spectrometer for charged 10-nanometer dust grains. These dust grains are released from Jupiters moon Io with typical rate of 1 kg s^1. The dust streams probe the plasma conditions in the Io plasma torus and can be used as a potential monitor of Ios volcanic plume activity. The other Galilean satellites are surrounded by tenuous impact-generated clouds of mostly sub-micrometer ejecta grains. Galileo measurements have demonstrated that impact-ejecta derived from hypervelocity impacts onto satellites are the major -- if not the only -- constituent of dusty planetary rings. We review the in-situ dust measurements at Jupiter and give an update of most recent results.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
