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.