2D materials and conjugated small molecules: from synthesis to devices for energy applications

Sammanfattning: The main goal of the present work is to contribute to the area of renewable energy storage, through the precise engineering of 2D materials and conjugated materials. Thus, four different types of graphene-based materials and a conjugated small molecule were synthesized in order to successfully develop supercapacitors. In the case of graphene-based materials, it was possible to modify its main parameters such as lateral dimensions, dispersibility, and energy levels. Furthermore, a new graphene-based material (SOG), that combines the advantages of GO and graphene without their disadvantages, was synthesized. SOG shows water dispersibility, a C/O ratio 260% higher than GO, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414.  The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, which is 75 times lower compared to GO. Moreover, the electrical resistance is nine orders of magnitude smaller (1.12 KΩ/sq) compared to GO. In order to analyze the feasibility of SOG for energy storage application, a swagelok-based supercapacitor was fabricated which exhibited remarkable characteristics such as 16 474 mF g-1 of gravimetric capacitance, and good retention at 10 000 mV s-1 of scan rate. SOG characteristics make it a promising new material for applications in organic electronics. Finally, a novel perylene diimide-based (PDI) and indacenodithieno[3,2-b]thiophene (IDTT) small molecule has been successfully synthesized and used for the first time as an organic-electrode supercapacitor. This new approach circumvents complex issues regarding the synthesis and purification of polymers. Promising results of a nanocomposite made of this SM and 10% SOG demonstrate a synergistic effect of 48.75% increase in the capacitance at 10 mA g-1, in two-electrode cells for a practical demonstration in energy storage. This study may open new possibilities for fabricating supercapacitors and multifunctional devices from conjugated small molecules and graphene-based materials.