Photoluminescence mechanism and optoelectronic responses of Janus pyrene and Janus coronene QDs for OLEDs & nanomedical applications

We carry out a first-principles study on manipulating the optoelectronic and photoluminescence properties of hexagonal and diamond-shaped graphene quantum dots, adopting asymmetric surface functionalization using hydrogen atoms on one side and molecular functional groups (-OH, -COOH, -CHO and -NH2) on the opposite side, leading to Janus quantum dots (JQDs). The results revealed considerable energetic and chemical stability characterizing the studied JQDs. In addition, the gap energy strongly depends on the variation of the shape and functionalization of the surface, giving rise to unexpected behaviour. Interestingly, the inclusion of quasiparticle corrections enhances the electronic character of all configurations, producing results in good agreement with experimental measurements. Optical absorption and excitonic binding energy are significantly altered by the basal plane decoration. At last, energy splitting of the excited states and TDDFT results have confirmed that our structures exhibit tunable photoluminescence from the near ultraviolet to the infrared region of the solar spectrum, making them promising for a new generation of applications.