Inorganic Ligand Thiosulfate-Capped Quantum Dots for Efficient Quantum Dot Sensitized Solar Cells

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Organic ligands on quantum dots (QDs) hinder photovoltaic applications due to their insulating properties.
• Replacing these with small, inorganic ligands is a promising strategy to enhance device performance.

Purpose of the Study:

• To investigate the efficacy of thiosulfate (S2O32-) and sulfide (S2-) as inorganic ligands for cadmium selenide (CdSe) quantum dots in quantum dot sensitized solar cells (QDSCs).
• To evaluate the impact of these inorganic ligands on the power conversion efficiency (PCE) and charge transfer dynamics in QDSCs.

Main Methods:

• Synthesized CdSe quantum dots capped with oleylamine (OAm), thiosulfate (S2O32-), and sulfide (S2-).
• Fabricated quantum dot sensitized solar cells (QDSCs) using these QDs as light-absorbing materials.
• Characterized QDSC performance using photovoltaic measurements, photoluminescence (PL) decay, and electrochemical impedance spectroscopy (EIS).

Main Results:

• Thiosulfate-capped CdSe QDs yielded a high PCE of 6.11%, significantly exceeding that of sulfide-capped (3.36%) and OAm-capped (0.84%) QDs.
• Thiosulfate-based QDSCs exhibited faster electron injection rates and enhanced charge-recombination resistance compared to sulfide- and OAm-based cells.
• The performance of thiosulfate-capped QDs is comparable to state-of-the-art mercaptocarboxylic acid-capped QDs.

Conclusions:

• Thiosulfate serves as an effective inorganic ligand for CdSe quantum dots in QDSCs, leading to significantly improved power conversion efficiency.
• The enhanced performance is attributed to faster electron injection and reduced charge recombination.
• This study introduces thiosulfate-capped QDs as a novel and efficient material for advancing QDSC technology.