Synthesis and characterization of a copper(II) phthalocyanine-based dye for organic photodetectors

Abstract

Novel copper(II) 4,4 ',4 '',4"'-tetra(hexylthienyl)phthalocyanine (CuPc-HT) was synthesized via Stille coupling reaction between 2-trimethylstannyl-5-hexylthiophene and tetra-brominated copper(II) phthalocyanine (CuPc). The incorporation of hexylthiophene to CuPc increased organic solubility, Q-band absorption and p-type characteristics. The bulk heterojunction organic photodetectors (OPDs) were developed by blending CuPc-HT with n-type [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM). CuPc-HT:PC71BM-based devices showed the strong green light detection in the range of 400-600 nm. The measured specific detectivity (D*) was 3.1 x 10(11) Jones under 530 nm light-emitting diode (LED) light of 0.1 mW/cm(2) at -2 V, which was approximately three times higher than those under 680 nm red LED irradiation. Dynamic characteristics of OPDs were investigated, and the -3 cut-off frequency of CuPc-HT:PC71BM devices was extremely high as 0.1 MHz. Notably, the signal response time at -1.0 V was ultrafast to be 9 mu s. Even though CuPc-HT:PC71BM devices showed insufficient static properties, their dynamic characteristics were comparable with those of state-of-the-art OPDs.