Coupling NiCo catalysts with carbon quantum dots on hematite photoanodes for highly efficient oxygen evolution

Highly efficient hole transfer from photoanodes to oxygen evolution catalysts is crucial for solar photoelectrochemical (PEC) water splitting. Herein, we demonstrated the coupling of NiCo catalysts with carbon quantum dots...

Síntesis, simulación y propiedades ópticas de un resorcinareno portador de quinolinas

El diseño y síntesis de macromoléculas orgánicas conjugadas es de interés en el área de la optoelectrónica, para la fabricación de dispositivos optoelectrónicos, tales como celdas solares orgánicas, celdas solares tipo perovskita, OLEDS, Transistores delgados de efecto de campo orgánicos, sensores, etc. En este trabajo se reporta la simulación molecular mediante DFT de un dendrímero de tipo resorcinareno con segmentos de quinolina y tiofeno en la periferia, designado como D. El dendrímero se sintetizo siguiendo el método convergente de acoplamiento del dendrón quinolínico al centro. El dendrímero D fue caracterizado mediante espectroscopia de 1H-RMN, FT-IR. El estudio de las propiedades ópticas se realizó mediante espectroscopia de UV vis y Fluorescencia estática y dinámica, los resultados indican que el dendrímero presenta una emisión máxima a 574 nm que se ubica en la región verde del espectroelectromagnético. El cálculo del band gap óptico y teórico fue de 2.78 y 3.3 eV respectivamente lo que ubica a este material, dentro de los semiconductores orgánicos. Los valores teóricos de los niveles de energía de los orbitales frontera HOMO y LUMO de 5.52 y 2.18 eV, sugieren su posible aplicación como HTL (hole transfer layer) en la fabricación de una celda solar orgánica de heterounión.

Effects of co-adsorption on interfacial charge transfer in a quantum dot@dye composite

The sensitive electronic environment at the quantum dot (QD)–dye interface becomes a roadblock to enhancing the energy conversion efficiency of dye-functionalized quantum dots (QDs). Energy alignments and electronic couplings are the critical factors governing the directions and rates of different charge transfer pathways at the interface, which are tunable by changing the specific linkage groups that connect a dye to the QD surface. The variation of specific anchors changes the binding configurations of a dye on the QD surface. In addition, the presence of a co-adsorbent changes the dipole–dipole and electronic interactions between a QD and a dye, resulting in different electronic environments at the interface. In the present work, we performed density functional theory (DFT)-based calculations to study the different binding configurations of N719 dye on the surface of a Cd33Se33 QD with a co-adsorbent D131 dye. The results revealed that the electronic couplings for electron transfer were greater than for hole transfer when the structure involved isocyanate groups as anchors. Such strong electronic couplings significantly stabilize the occupied states of the dye, pushing them deep inside the valence band of the QD and making hole transfer in these structures thermodynamically unfavourable. When carboxylates were involved as anchors, the electronic couplings for hole transfer were comparable to electron transfer, implying efficient charge separation at the QD–dye interface and reduced electron–hole recombination within the QD. We also found that the electronic couplings for electron transfer were larger than those for back electron transfer, suggesting efficient charge separation in photoexcited QDs. Overall, the current computational study reveals some fundamental aspects of the relationship between the interfacial charge transfer for QD@dye composites and their morphologies which benefit the design of QD-based nanomaterials for photovoltaic applications.