Excitons formation

The design of the organic LEDs should be optimized so that the double charge injection factor and the probability for singlet exciton formation is near to unitv... 

Characteristically, the mechanisms formulated for azide decompositions involve [693,717] exciton formation and/or the participation of mobile electrons, positive holes and interstitial ions. Information concerning the energy requirements for the production, mobility and other relevant properties of these lattice imperfections can often be obtained from spectral data and electrical measurements. The interpretation of decomposition kinetics has often been profitably considered with reference to rates of photolysis. Accordingly, proposed reaction mechanisms have included consideration of trapping, transportation and interactions between possible energetic participants, and the steps involved can be characterized in greater detail than has been found possible in the decompositions of most other types of solids. 

Z Shuai, D Beljonne, RJ Silbey, and JL Bredas, Singlet and triplet excitons formation rates in conjugated polymer light-emitting diodes, Phys. Rev. Lett., 84 131-134, 2000. 

Phosphorescence as a probe of exciton formation and energy transfer in organic light emitting diodes M. Baldo, M. Segal Physica Status Solid A Applied Research, 201 1205-1214... 

Exciton formation Exciton formation Exciton formation... 

JS Wilson, AS Dhoot, AJAB Seeley, MS Khan, A Kohler, and RH Friend, Spin-dependent exciton, formation in TT-conjugated compounds, Nature, 413 828-831, 2001. 

A Kohler and J Wilson, Phosphorescence and spin-dependent exciton formation in conjugated polymers, Org. Electron., 4 179-189, 2003. 

Exciton formation The holes and electrons must combine in the emitter region of the device via a Coulombic interaction to form excitons [67] (neutral excited species) other excited states are also possible such as excimer [68] or exciplex excited states [69,70]. 

Figure 7.6 shows typcial current density-voltage-luminance (J-V-L) and emission characteristics of an OLED device. OLEDs have a similar electrical characteristic to that of a rectifying diode. In forward bias, the device starts with a small current at low voltages. In this region, charge carriers are injected into the device but little exciton formation, hence light... 

In general, a two-layer device structure is more efficient than single-layer architectures. There are two key reasons for this. First, each layer can be separately optimized for the injection and transport of one carrier type. Second, exciton formation and radiative decay take place close to the HTL-ETL interface away from the quenching sites at the organic-metal contacts. 

Fig. 3 Cartoon of exciton formation, migration, and recombination (radiative and nonradiative)...

Roberts ST, Schlenker CW, Barlier VS, McAnally RE, Zhang Y, Mastron JN, Thompson ME, Bradforth SE (2011) Observation of triplet exciton formation in a platinum sensitized organic photovoltaic device. J Phys Chem Lett 2 48... 

From the theoretical point of view, there are two ways in which free carriers can affect exciton formation. 

Many authors have investigated the photoconductivity of the polydiacetylenes [142-171], The main problem discussed concerns the nature of the initial act of the photoeffect. At first, most authors considered the exciton formation to occur at the beginning with consequent dissociation on the free carriers. Then it was shown the broad band existence for directions along the chains. The unification of the excitonic and band model of the free charge carrier generation was developed [146-150],... 

For Ag, the decay time values were found similar to those reported in ref. [1, 2] providing information about the electron-phonon scattering. For Fe203, several other phenomena could cause the OD changes at the ultrafast time scale. The sub-picosecond and picosecond decay times allow to take into account hot electron thermalization [4] and subsequent fast relaxation processes such as exciton formation or surface traps filling [6]. 

There are some recent application of a mixed quantum classical description to investigate quantum dynamics in large CC. The absorbance of a photosynthetic light harvesting complex caused by electronic Frenkel-exciton formation has been considered in Ref. [23], and Refs. [24,25] focused on excitation energy transfer in a DNA double helix strand. In both cases, however, the considerations have been restricted to an approximate description based on the use of... 

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