Light induced modulation of charge transport phenomena across the bistability region in [Fe(Htrz)2(trz)](BF4) spin crossover micro-rods

We studied the effect of light irradiation on the electrical conductance of micro-rods of the spin crossover [Fe(Htrz)2(trz)](BF4) network, organized between interdigitated gold electrodes. By irradiating the sample with different wavelengths (between 295 and 655 nm) either in air or under a nitrogen atmosphere we observed both a reversible and an irreversible change of the current flowing in the device. The reversible process consists of an abrupt decrease of the current intensity (ca. 10–50%) upon light irradiation, while the irreversible process is characterized by a slow, but continuous increase in time of the current, which persists also in the dark. These photo-induced processes were only detected in the high conductance low-spin (LS) state of the complex. On switching the rods to the high spin (HS) state the conductance decreases two orders of magnitude (at the same temperature) and – as a consequence – the photo-effect vanishes.