Effects of surface engineering of PbS core and CdSxSe1-x/ZnSe core/shell quantum dots on optoelectronic properties

Date

2025-1-9

Author

Aydın, Firdevs

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Quantum dots (QDs) are extraordinary materials due to their ease of tuning optical&electronic properties. However, surface defects together with their high surface-to-volume ratio limit their performance in optoelectronics. This study explores defect mitigation strategies for QDs such as PbS, CdS, CdSe, and CdSxSe1−x to enhance their performance parameters in fields such as solar cells and detectors. Additionally, the effects of surface passivation (SP) and heterojunction type on the charge decay characteristics of polymers were investigated. In this study, CdS/PbS bilayer solar cells, where PbS QDs were synthesized and ligand exchanged using conventional techniques, were fabricated. Utilizing electrodeposited CdS as the electron transport layer and doping with carbon QDs resulted in enhanced morphology and reduced defects, achieving an efficiency of 6.79%. In addition, a new direct synthesis-DS protocol was developed for the PbS QDs and photodetectors fabricated with the developed new protocol, achieved detectivities in the range of 11×1012 Jones. Furthermore, a novel in-situ metal halide SP strategy was developed for DS-PbS QDs, and treatment with CdI2 resulted in a promising PCE of 7.92%. Additionally, defect control was achieved by overcoating core QDs with a high bandgap shell material. This approach led to profound effects on the excited state dynamics and antistatic behavior of polymers. Later, alloying approach was used to control composition dependent defects in core and tune the heterojunction type. Finally, the heterojunction type was validated further by studying the charge decay mechanisms of the polymers embedded with alloy core-shell QDs. These advancements highlight the promise of innovative QD architectures and surface passivation in enhancing the efficiency of next-generation optoelectronic devices.

Subject Keywords

Quantum Dots, Surface Passivation, Solar Cells, Core-Shell QDs, Antistatic

URI

https://hdl.handle.net/11511/113517

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Graduate School of Natural and Applied Sciences, Thesis