1:15 PM - 1:30 PM
▲ [6p-S44-1] [JSAP Young Scientist Award Speech] Application-oriented electronic structure engineering in colloidal quantum dot solids
Keywords:colloidal quantum dot, semiconductor nanocrystal, electronic transport
Colloidal quantum dots (CQDs) are semiconductor nanocrystals soluble in common organic solvents, combining the flexibility and low cost of solution-processed materials and the durability and high mobility of the inorganic core. Moreover, the presence of quantum confinement and the large surface-to-volume ratio allow for wide control of the optical and electronic properties such as the band gap, carrier mobility and concentration, all by simple, chemical methods. The particle size, the ligands attached to the surface and the environment play the most important roles in tailoring the material’s behavior.
For a long time, lead-chalcogenide CQD films were thought to be p-type, which was mainly caused by the oxidative environment used for processing and characterization. Once these factors were under control, and more air-stable chemical treatments were introduced, the materials became predominantly n-type. The consequent change in the device structure allowed for boost in the solar cell performances, and set the lack of stable p-type material as the limiting factor in the development. It has been predicted that the lead-to-sulfur ratio in PbS CQDs influences the electronic structure, offering a prospective solution.
In this work, I present a method to fine-tune the layer stoichiometry in order to enhance the hole mobility and the effective p-doping of PbS CQD films. The hole mobility increases 3 orders of magnitudes, while the electron mobility remains the same, pointing to an altered electronic structure as the cause of the change. The developed method was proven useful in improving the photoconversion efficiencies of PbQ CQD solar cells through parallel mobility and hole concentration increase. Further improvement of the method might allow the observation of a strong Seebeck-effect in PbS CQD films, which is promising for their applications in thermoelectric devices.
For a long time, lead-chalcogenide CQD films were thought to be p-type, which was mainly caused by the oxidative environment used for processing and characterization. Once these factors were under control, and more air-stable chemical treatments were introduced, the materials became predominantly n-type. The consequent change in the device structure allowed for boost in the solar cell performances, and set the lack of stable p-type material as the limiting factor in the development. It has been predicted that the lead-to-sulfur ratio in PbS CQDs influences the electronic structure, offering a prospective solution.
In this work, I present a method to fine-tune the layer stoichiometry in order to enhance the hole mobility and the effective p-doping of PbS CQD films. The hole mobility increases 3 orders of magnitudes, while the electron mobility remains the same, pointing to an altered electronic structure as the cause of the change. The developed method was proven useful in improving the photoconversion efficiencies of PbQ CQD solar cells through parallel mobility and hole concentration increase. Further improvement of the method might allow the observation of a strong Seebeck-effect in PbS CQD films, which is promising for their applications in thermoelectric devices.