Photoinduced negative magnetoresistance in 6,13-bis(triisopropylsilylethynyl)-pentacene field-effect transistors

We report on photoinduced negative organic magnetoresistance in low external magnetic-fields (<100 mT) in 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-Pentacene) field-effect transistors. An external magnetic field does not influence the dark current of our device. In contrast, there is a significant increase in photocurrent when magnetic field is applied to the irradiated device, which leads to negative magnetoresistance. The magnetoresistance and photoresponse values are strongly correlated and both are influenced by applied voltages and irradiation intensity. We attribute the observed photoinduced negative magnetoresistance in TIPS-Pentacene field-effect transistors to the presence of electron-hole pairs under irradiation. The overall dissociation probability of electron-hole pairs rises under the influence of an external magnetic field, which leads to a higher number of free charge carriers.

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► Photoinduced (λ = 671 ± 7 nm) negative magnetoresistance in TIPS-Pentacene OFETs.
► The effect can only be observed if the device is irradiated.
► The dissociation probability of electron–hole pairs rises under magnetic field.
► A magnetoresistance of ∼0.57% is obtained at 296 μW and a magnetic field of 60 mT.