Optical switching of carrier transport in polymeric transistors with photochromic spiropyran molecules

We demonstrate the optical switching of transistor properties by adopting the photoisomerization of spiropyran (SP) molecules dispersed in a poly(triarylamine) (PTAA) channel layer. The drain current (IDS) was reduced by ultra-violet (UV) light irradiation, while visible (VIS) light irradiation restored the IDS to its original value. The UV and VIS light irradiation brought about the photoisomerization reactions of SP, i.e., an ionic polarized open-ring isomer was induced by UV and a less polarized closed-ring isomer was induced by VIS. To clarify the mechanism of the photoisomerization-induced optical switching, we evaluated the variations in transistor properties, namely IDS, carrier mobility and threshold voltage, when subjected to UV and VIS light irradiation. We found that the ionic polarized open-ring SP isomer worked as a carrier scattering site that effectively suppressed carrier transport in the polymer channel.