Quantum Dots with Conjugated Ligands for Optoelectronic Applications

Currently, the engineering of low-cost and efficacious nanomaterials and thin films for use in optoelectronics is gaining considerable attention. Perovskite quantum dots (QDs), e.g. CsPbX3 and CdSe/ZnS emits light green light and form some of the least expensive substances for this purpose. Typically, the production of these QDs, in which the dimensions are regulated, necessitates the utilisation of organic ligands with long alkyl chains, e.g. oleic acid. These passivating ligands enable the solubility of QDs in solvents, however, they have the drawback that their poor charge transference capacity encompasses the perovskite QD surface and behaves as an insulating layer. This causes a reduced photocurrent and diminishes the efficacy of power transformation. The aim of the current study is to design new inorganic/organic hybrid nanomaterials comprising perovskite as well as CdSe/ZnS QDs, using novel semiconducting organic ligands as capping agents in order to circumvent the disadvantages of routine capping substances and to promote QD output. To date, few studies have been published in this area, and the correlation between the ligand properties and their influence on the photophysical and electroluminescent characteristics requires further elucidation. In this work tow novel semiconducting ligands have been successfully synthesized. The first ligand is terfluorene, 4-ter(9,9-dioctylfluoren 2,2':7',2''-2-yl)-benzoic acid, bandgap 2.95 eV was used as the shell for the combination inorganic/organic QDs. Active substances, such fluorene oligomers have been utilised in organic photovoltaic cells, optoelectronic devices and light-emitting diodes, respectively. Technological progression has enabled their use as key electroluminescent substances which emanate intense blue light emission, owing to the elevated hole mobility and refinable characteristics that can be regulated with easy chemical modifications and co-polymerisation. Attributes of such substances encompass enhanced thermal stability, solubility and photoluminescent quantum yield, as well as straightforward low-cost synthetic techniques. Moreover, these materials maintain their integrity in air and moisture; self-assembly under water has additionally been verified.