Metal-Ligand Complex-Induced Ultrafast Charge-Carrier Relaxation and Charge-Transfer Dynamics in CdX (X=S, Se, Te) Quantum Dots Sensitized with Nitrocatechol

Visible light-induced hole transfer in single-nanoplate Cu1.81S-CdS heterostructures

The separation and transfer of photogenerated carriers in semiconducting materials are essential processes that determine the efficiency of optoelectronic devices and photocatalysts, and transient absorption spectroscopy provides a powerful support for exploring the diffusion and recombination of photogenerated electrons and holes. Herein, high-quality Cu1.81S nanoplates were synthesized by a hot injection method, and were used as starting templates for the preparation of Cu1.81S-CdS heterojunctions and CdS nanoplates by cation exchange. Their carrier dynamics were investigated by transient absorption spectroscopy, which revealed that photogenerated holes may be transferred from the CdS phase to the Cu1.81S phase under 400 nm excitation. This process is in the opposite direction to the hole transfer induced by near-infrared localized surface plasmon resonance in copper sulfide heterostructures. Moreover, density functional theory calculations were used to further explain the visible light-induced hole transport process. This transfer is a potential way to increase the rate of H2 production and enhance the photostability of the catalyst.

Strategies for extending charge separation in colloidal nanostructured quantum dot materials

Semiconductor colloidal metal chalcogenides (II-VI) in the form of quantum dots (QDs) and different heterostructures (core/shell, alloys, etc.) are of extensive interest in scientific research for both a fundamental understanding and technological applications because of their quantized size and different optical properties; however, due to their small size, the exciton (bound electron and hole) experiences a strong Coulombic attraction, which has a remarkable impact on the charge separation and photophysical properties of QDs. Thus, to achieve an efficient charge separation, numerous attempts have been made via the formation of different heterostructures, QD/molecular adsorbate (either organic or inorganic) assemblies, etc. These hybrid materials ameliorated the absorption of the incident light as well as charge separation. This article reviews the strategies for extending charge separation in these colloidal nanocrystals (NCs), which is one of the crucial steps to elevate the solar to electrical energy conversion efficiency in a quantum dot-sensitized solar cell (QDSC). The article summarizes the benefits of co-sensitization and experimental shreds of evidence for the multiple charge transfer processes involved in a QDSC. Studies have shown that in the co-sensitization process, prolonged charge separation occurs via the dual behavior of the molecular adsorbate, sensitization (electron injection) and capture of holes from photoexcited QDs. This perspective emphases band edge engineering and control of charge carrier dynamics in various core/shell structures. The impact of colloidal alloy NCs on charge separation and interesting photophysical properties was recapitulated via the steady-state and time-resolved photoluminescence (PL) and femtosecond transient absorption spectroscopic techniques. Finally, the prolonged lifetime and extent of charge separation for these hybrid NCs (or the composites) assisted in the development of a better light harvester as compared to the case of their pure counterparts.

Synthesis and supramolecular organization of chiral poly(thiophene)–magnetite hybrid nanoparticles

Fe₃O₄ nanoparticles decorated with a conjugated polymer is synthesized and the supramolecular organization of the polymer is studied.