Ligand-customized colloidal quantum dots for high-performance optoelectronic devices

Abstract

Colloidal quantum dots (CQDs) have attracted considerable attention owing to their potential applications in low-cost and high-performance optoelectronic devices. Achieving electronic-grade CQD materials requires precise control over their semiconducting properties via surface management. Herein, we developed a new surface modification strategy that allows for enhanced control over both the type and the amount of ligands by decoupling colloidal-stabilization and property-engineering ligands. This enables the fine control of the electronic properties of CQD materials. Using PbS CQDs, we showed improved passivation and suppressed band tail states. The resultant solar cells exhibited a higher power conversion efficiency of 13.3% compared to the 10.4% efficiency of the control device, and photodetectors showed a detectivity (D*) of 1.8 × 10¹² Jones, which is a more than four-fold improvement in comparison to the control devices. Moreover, the versatility of this approach was evaluated in other CQD systems, including emissive CdSe/ZnCdSe/ZnSe core/shell and infrared HgTe CQDs. The high photoluminescence quantum yield of CdSe/ZnCdSe/ZnSe core/shell CQDs was well preserved in polar solvents following a solution ligand exchange process, and tunable doping of HgTe CQDs was achieved. Overall, this ligand-customization approach verifies the significance of fine control of ligands towards the development of electronic-grade CQD materials, which might have implications for other QD materials.