Photoinduced valence instability in the organic molecular compound tetrathiafulvalene-p-chloranil (TTF-CA)

It was found that a local charge-transfer excitation on the donor(D)-acceptor(A) pair leads to a semimacroscopic valence change from the quasi-ionic (${\mathit{D}}^{+}$ ${\mathit{A}}^{\mathrm{-}}$) to quasineutral (${\mathit{D}}^0$ ${\mathit{A}}^0$) states in organic molecular-compound TTF-chloranil with mixed DA stacks. Photogenerated neutral-ionic domain walls, which are responsible for anomalous photoconductivity, show the temporal annihilation due to the one-dimensional recombination.