Conformation-Induced Electrostatic Gating of the Conduction of Spiropyran-Coated Organic Thin-Film Transistors

A facile method to make optoelectronic devices formed from organic thin-film transistors that are functionalized by photochromic spiropyran dyes in a nondestructive manner has been developed. When PDMS stamps are employed, alkane-containing spiropyran molecules can be coated simply onto the surface of organic thin films in a noninvasive manner. Upon UV irradiation, the molecules undergo isomerization from the neutral closed form to the charge-separated merocyanine form, producing the local electrostatic environment. This photoinduced electrostatic environment can function as a local negative gate voltage, thus increasing the electrical conductivity in p-type devices and decreasing the electrical conductivity in n-type devices. Further irradiation with visible light or keeping the devices in the dark can switch the device conductance back to their initial value. This method is reversible and reproducible on different devices with different thickness over a long period of time.