Effect of Chalcogen Atom on the Properties of Naphthobischalcogenadiazole-Based π-Conjugated Polymers

Abstract

We here discuss the effect of chalcogen atom on the properties of π-conjugated polymers based on electron deficient fused π-electron systems, naphtho[1,2-c:5,6-c′]bis[1,2,5]oxadiazole (NOz), naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NTz), and naphtho[1,2-c:5,6-c′]bis[1,2,5]selenadiazole (NSz). We synthesize new donor–acceptor polymers having NOz and NSz combined with a quaterthiophene donor unit, namely, PNOz4T and PNSz4T, respectively. Physicochemical properties, structures, and charge transport properties of PNOz4T and PNSz4T in comparison with the sulfur analogue (PNTz4T) are discussed. As both NOz and NSz have a higher electron deficient nature than NTz, PNOz4T and PNSz4T are found to possess deeper frontier orbital energy levels. In particular, PNOz4T have a sufficiently deep lowest unoccupied molecular orbital (LUMO) energy level which allows for ambient ambipolar behavior in transistor devices. Interestingly, whereas PNSz4T is mostly amorphous in the thin film, PNOz4T forms a highly crystalline s...