A Unique Sandwich Structure Consisting of Graphene and Pyrene Derivatives for Ultraviolet Light Sensor.

We propose and demonstrate, for the first time, a sandwich structure of graphene substrates, pyrene derivatives, and an electrolyte for ultraviolet light sensing. A contact capacitor forms at the graphene-electrolyte interface via the electric double layer. When ultraviolet light excites the interlayer of the pyrene derivative, a photo-generated electric field changes the carrier density in graphene, affecting its conductivity. Thus, the sandwich structure responds to ultraviolet light intensity, which is monitored by current changes in different states. Linear fitting shows a strong positive relationship between UV intensity and current (Ids), with R2 above 0.99 and excellent reproducibility. The responsivity (R) and response time (τr) for the measurement at a distance of 50 cm are estimated as 0.7 A/W and 70 s, respectively.