Multiband Photoresponding Field-Effect Transistor Memory Using Conjugated Block Copolymers with Pendent Isoindigo Coils as a Polymer Electret

In this study, the authors report a series of conjugated block copolymers, PF-b-Piso comprising poly[2,7-(9,9-dihexylfluorene)] (PF), and poly(pendent isoindigo) (Piso) for polymer electret in the photonic field-effect transistor (FET) memory device. The optical properties, surface morphology, and molecular organization of these BCPs are investigated systematically. Accordingly, Piso with absorption in the Ultraviolet C range (UVC, 200-280 nm) possibly rendered the device with a multiband photoresponse, and a good memory performance is achieved by optimizing the polymer composition. Therefore, the memory device comprising PF-b-Piso could perform a high current contrast of 10(6) to 40(5) nm light and 10(5) to 254 nm light over 10(4) s. In addition, a current contrast of 10(4) and 10(2) is achieved in response to 650 and 530 nm light, and this phenomenon can be attributed to the charge transfer between channel and memory layers. The experimental results indicate that the block copolymer design not only conduces to forming a self-assembled microphase separation to stabilize the trapped charge in the polymer electret, but also triggers multiband photoresponding of the photonic FET memory.