The photo-induced phase transition in Et2Me2Sb[Pd(dmit)2]2

The large photo‐induced change of reflectivity has been observed in the unique charge separated phase of the Et2Me2Sb[Pd(dmit)2]2 crystal. We observe a clear spectral change due to the disappearance of the charge separated phase by femtosecond photo‐excitation in the [Pd(dmit)2] dimer. The dynamics of the photo‐excited state depends on the excitation intensity. Obtained results strongly suggest that cooperative effect plays a key role in the photo‐excited state of this system. We tentatively classify the observed phenomena as a photo‐induced phase transition due to the melting of the charge separation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)