Formation of PCDTBT:PC71BM p–n junction composite nanotubes via a templating method

Abstract

The use of a templating method to synthesize a p–n junction composite of poly[N-90-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thie-nyl 20,10,30 benzothiadiazole)] (PCDTBT):[6,6]-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM) is reported in this study. These materials have been studied due to their potential applications in organic electronic-based devices. Intimate contact between these materials can be realised via a facile fabrication using the template-assisted method. The formation of a p–n junction composite was elaborated in which its properties were compared to its bulk heterojunction counterpart. PCDTBT nanorods, nanotubes and nanoflowers were first produced followed by infiltration of PC₇₁BM. A remarkable pattern at the first peak (carbazole) could be seen from the UV-vis spectra of the PCDTBT:PC₇₁BM p–n junction composite nanotubes at a higher concentration of 15 mg ml⁻¹. However, the reverse condition was seen for its lower concentration of 5 mg ml⁻¹, which showed improvement in the second peak (DTBT) in the UV-vis spectra. The first peak of the 10 mg ml⁻¹ solution concentration shows a wider peak compared to the 5 and 15 mg ml⁻¹ concentrations with its second peak having fallen between these two concentrations. Unlike the PCDTBT:PC₇₁BM bulk-heterojunction, which showed better quenching, PCDTBT:PC₇₁BM composite nanotubes have shown a significant red-shift in their photoluminescence (PL) spectra. Despite having a significant red-shift, the PCDTBT:PC₇₁BM junction composites displayed poor quenching properties.