ABSTRACT
Solution-processed organic-inorganic hybrid perovskites are promising emitters for next-generation optoelectronic devices. Multiple-colored, bright light emission is achieved by tuning their composition and structures. However, there is very little research on exploring optically active organic cations for hybrid perovskites. Here, unique room-temperature phosphorescence from hybrid perovskites is reported by employing novel organic cations. Efficient room-temperature phosphorescence is activated by designing a mixed-cation perovskite system to suppress nonradiative recombination. Multiple-colored phosphorescence is achieved by molecular design. Moreover, the emission lifetime can be tuned by varying the perovskite composition to achieve persistent luminescence. Efficient room-temperature phosphorescence is demonstrated in hybrid perovskites that originates from the triplet states of the organic cations, opening a new dimension to the further development of perovskite emitters with novel functional organic cations for versatile display applications.
ABSTRACT
Using a three-dimensional spin polarimeter we have gathered evidence for the interference of spin states in photoemission from the surface alloy Sb/Ag(111). This system features a small Rashba-type spin splitting of a size comparable to the momentum broadening of the quasiparticles, thus causing an intrinsic overlap between states with orthogonal spinors. Besides a small spin polarization caused by the spin splitting, we observe a large spin polarization component in the plane normal to the quantization axis of the Rashba effect. Strongly suggestive of coherent spin rotation, this effect is largely independent of the photon energy and photon polarization.
Subject(s)
Alloys/chemistry , Antimony/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Silver/chemistry , Light , Materials Testing , Particle Size , Spin LabelsABSTRACT
The influence of structural defects, in the form of step lattices, on the spin polarization of the spin-orbit split Shockley surface state of Au(111) has been investigated. Spin- and angle-resolved photoemission data from three vicinal surfaces with different step densities are presented. The spin splitting is preserved in all three cases, and there is no reduction of the spin polarization of individual subbands, including the umklapp bands induced by the step lattice. On the sample with the highest step density studied, where the wave functions are delocalized over several terraces, the spin splitting is enhanced substantially, likely as an effect of the effective surface corrugation as on related surface alloys. The spin texture shows in all cases spin polarization vectors tangential to the Fermi circles, with the same helicities as on Au(111).
ABSTRACT
The properties of crystalline solids can to a large extent be derived from the scale and dimensionality of periodic arrays of coupled quantum systems such as atoms and molecules. Periodic quantum confinement in two dimensions has been elusive on surfaces, mainly because of the challenge to produce regular nanopatterned structures that can trap electronic states. We report that the two-dimensional free electron gas of the Cu(111) surface state can be trapped within the pores of an organic nanoporous network, which can be regarded as a regular array of quantum dots. Moreover, a shallow dispersive electronic band structure is formed, which is indicative of electronic coupling between neighboring pore states.
ABSTRACT
A Rashba-type spin-orbit splitting is found for quantum well states formed in ultrathin Pb films on Si (111). The resulting momentum splitting is comparable to what is found for semiconductor heterostructures. The splitting shows no coverage dependency and the sign of the spin polarization is reversed compared to Rashba splitting in the Au(111) surface state. We explain our results by competing effects at the two boundaries of the Pb layer.
