Exciton transport

DSSCs convert sunlight to electricity by a different mechanism than conventional p-n junction solar cell. Light is absorbed directly at the solid/liquid interface by a monolayer of adsorbed dye, and initial charge separation occurs without the need of exciton transport.42,43 Following the initial charge separation, electrons and holes are confined in two different chemical phases electrons in the nanocrystalline... 

Exciton States and Exciton Transport in Molecular Crystals... 

However, the available theories have still been restricted to selected parameter orderings. In particular, it has been assumed in theories of exciton transport that the exciton bandwidth is narrower than the phonon bandwidth, and this assumption has been carried over to theories of carrier transport. In fact, carrier bandwidths may well be much larger than phonon bandwidths at low temperatures, becoming smaller than phonon bandwidths as the temperature is raised, owing to polaron band narrowing... 

A theory of exciton-phonon coupling is presented and the consequences of this coupling for spectral line shapes and exciton transport are discussed. The theory is valid for arbitrary phonon and exciton bandwidths and for arbitrary exciton phonon coupling strengths. The dependence of the diffusion constant on temperature and the other parameters is analyzed. 

Can we increase the efficiency of exciton transport in amphi-PIC J-aggregates We have to take into consideration a large disorder degree observed in amphi-PIC J-aggregates that leads to different localization effects which influence exciton dynamics in amphi-PIC J-aggregates [5]. One of the... 

Electronic excitations in molecular aggregates have received considerable attention from theoretists and experimentalists in recent years. Much of the work has focused on excitonic transport in molecular crystals (J.), in sub s t i t u 11 o na 11 y disordered mixed crystals (2.) and in amorphous structures (3.). Furthermore, excitation energy transfer (EET) has been studied in fluorescence concentration depolarization of donor molecules in solution (4.) as well as in excited-state energy transfer of donor -acceptor dyes in condensed phase systems (5.). 

An extensive discussion of experiments on exciton transport in isotopically disordered crystals and numerical simulations of this phenomenon in the framework of a percolation model may be found in the review paper by Kopel-mann (20). A more recent review of this field, including the discussion of the Anderson model, may be found in the book by Pope and Swenberg (21). 

FIGURE 8.4 Schematic drawing of the operation of a hilayer photovoltaic cell (in this example and ITO/Ti02/MEH-PPV/Au device) showing (a) light absorption, (b) exciton transport, (c) exciton dissociation, and (d) collection of electrons at the anode and (e) holes... 

Tant, J., Geerts, Y.H., Lehmann, M., De Cupere, V, Zucchi, G., Laursen, B.W., Bjornhohn, T., Lemaur, V, Marcq, V., Burquel, A., Hennebicq, E., Gardebien, E, Viville, P., Beljonne, D., Lazzaroni, R., and Comil, J., Liquid crystalline metal-free phthalocyanines designed for charge and exciton transport, J. Phys. Chem. B, 109, 20315, 2005. 

The dibromonaphthalene (DBN) crystal differs in its crystal structure (Fig. 2.14) considerably from the structure of the polyacene crystals (Fig. 2.10) the unit cell of DBN contains eight molecules, which belong to two non-equivalent sublattices I and II. The excitation energies of the triplet excitons in the sublattices I and II differ by 50 cm. At low temperatures, therefore, only the excitons in one of the sublattices are excited. Each sublattice consists of linear stacks of DBN molecules along the c axis of the crystal. The exciton transport along this stacking axis is also predominant the triplet excitons in in DBN crystals are quasi-one-dimensional excitons. 

H. R. Kerp and E. E. van Eaassen. Effects of oxygen on exciton transport in zinc phthalocyanine layers. Chem. Phys. Lett., 332(l-2) 5-12, December 2000. 

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