This project is to tackle the challenge of gaining controlled functions of organic semiconductors using extended polycyclic aromatic hydrocarbons (PAHs), encoding the functionalization that defines the properties and the self-assembly properties via a site-specific doping of the aromatic framework.
The aim of this project can be achieved through the substitution of the C=C bonds with isostructural and isoelectronic boron-nitrogen couples (BN) and exploiting the polarity of their bonds to program the functional properties. By changing the dopant/carbon ratio and the doping pattern, one can tailor the desired chemical, optical, heat dissipation and molecular recognition properties of the organic semiconductor.
The idea is to prepare materials for two main applications:small molecule gas sensing and thermal management.
Project aims and methods
Scientific Objectives (SOs1-4). You will prepare molecular graphenes starting from structurally programmed dendritic precursors (SOs1&2) in which aryl units are substituted in given positions with borazine rings (B3N3). It is envisaged that the planarization (SO3) will yield the formation of molecular graphenes featuring doping units arranged in a predetermined pattern (SOs4). This will lead to isoelectronic fully planar p-conjugated modules each encoded with a specific BN-doping pattern and concentration, the latter dictating both the energy bandgap, thermal dissipation and chemical recognition properties.
The first part of the project will be centered on the development of synthetic methodologies allowing the controlled insertion of B3N3-rings into nanographene structures.
The expected academic returns are:
1.control on the concentration and arrangement of the doping units
2.establishment of a doping/property relation.
Technologic Objectives (TOs1-2).By engineering top-gate bottom-contact (TGBC) and bottom-gate bottom-contact (BGBC) devices, we will measure the charge-carrier mobilities of the materials as thin films and nanostructure morphologies.
The devices will then be exposed to gases (CO2, CO). A specific binding of the compounds is expected to occur selectively at the polar doping sites, ultimately affecting the source-drain current of the transistors(TO1). Given the close proximity between the analytes and the semiconducting materials, the best sensing system prototype is expected to achieve detections limits down to the femto molar range, with a low-cost, reliable sensing technology.
A pronounced variation in the selectivity is expected when operating with materials doped with different doping concentrations. In a second avenue, we will investigate the heat dissipation properties of the semiconductor (TO2).In general,all electronic devices and circuitry generate excess heat and thus require thermal management to improve reliability and prevent premature failure. In order to make efficient and cost-effective the removal of dissipated thermal energy from any devices, current technologies (e.g., heat sinks, thermoelectric coolers, forced air systems and fans, heat pipes to name a few) should be coupled with materials displaying high thermal conductivity.
Given the high thermal conductivity of boron nitride (BN), it is expected that the molecules developed in this project can replace current semiconductors and allow the development of even smaller devices and make our mobile phones and computers cooler and safer.
Start date: 1st October 2019
Supervisor: Professor Davide Bonifazi - https://www.cardiff.ac.uk/people/view/161126-Bonifazi-Davide