Charge transfer state dissociation

Braun derived an expression for k E) from the 1934 Onsager theory by use of the expression given by Fuoss and Accascina (1959) and Eigen et al. (1964) for the zero-field equilibrium constant for the dissociation of an ion pair. Assuming a field-independent lifetime, Braun determined the field dependence of the charge-transfer state dissociation probability as... 

Figure 6 The field dependencies of the charge-transfer state dissociation probability based on the ion-pair approximation and a 8 function of ion-pair separation distances.

Onsager-Braun Model of Charge-Transfer State Dissociation... 

Copper-reconstituted cytochrome c ( cyt-c) has also been investigated with transient absorption methods (49). No evidence of ghotoinduced ejection of the fifth ligand is observed in either cyt-c or the model Cu-porphyrin 5-coordinate complexes (60-62). This is consistent with the likely transient state being a non-dissociative w w or d 2 2 charge-transfer state. 

Lee J, Vandewal K, Yost SR, Bahlke ME, Goris L, Baldo MA, Manca JV, Van Voorhis T (2010) Charge transfer state versus hot exciton dissociation in polymer-fullerene blended solar cells. J Am Chem Soc 132 11878... 

Braun CL (1984) Electric-field assisted dissociation of charge-transfer states as amechanism of photocarrier production. J Chem Phys 80 4157... 

In this case, the ethylamine radical is formed by hydrogen abstraction from the solvent, instead of dissociation of the excited (charge-transfer) state of the amide ion pair. 

In Refs. [50-53], two levels of analysis were successively addressed (i) a two-state XT-CT model which is able to capture the basic features of the phonon-mediated exciton dissociation process (ii) a three-state XT-IS-CT model which also comprises an intermediate state (IS), i.e., an additional charge transfer state whose presence can have a significant influence on the dynamics, see Fig. 6. In the latter case, comparative calculations for several interface configurations were carried out, leading to a realistic, molecular-level picture of the photophysical events at the heterojunction. In the following, we start with a summary of the findings reported in Refs. [50,51], where the two-state model was explored (Sec. 5.1). Following this, we address in more detail the analysis of Refs. [52,53] for the three-state model (Sec. 5.2). 

Regarding the role of intermediate states, we have focused on an additional charge transfer state which exhibits a non-negligible coupling to the exciton state and could therefore play a significant role in the exciton dissociation dynamics. Recent experimental studies provide strong indications that such an... 

Figure 48 Photo-excitation and dissociation of Alq3, leading to the charge transfer state (CT) and electron-hole pairs, the latter giving rise to photocurrent flowing in solid Alq3.

Geminate recombination is the recombination of an electron with its parent cation. Geminate recombination models are premised on the assumption that the formation of a free electron-hole pair involves the dissociation of an intermediate charge-transfer state. Early models were based on the Poole-Frenkel effect. Most recent models have been based on theories due to Onsager. 

Yasunaga et al. (1979) studied photoconductivity of single crystals of PbPc doped with O. The photocurrent increased sharply with increasing O. The results were explained by the ionization of a charge-transfer state created by the dissociation of a triplet exciton. The exciton dissociation was suggested to occur at crystal sites occupied by O. 

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