Macrocyclic Compounds: Metal Oxide Particles Nanocomposite Thin Films Deposited by MAPLE

Nanocomposite films based on macrocyclic compounds (zinc phthalocyanine (ZnPc) and 5,10,15,20-tetra(4-pyridyl) 21H,23H-porphyrin (TPyP)) and metal oxide nanoparticles (ZnO or CuO) were deposited by matrix-assisted pulsed laser evaporation (MAPLE). 1,4-dioxane was used as a solvent in the preparation of MAPLE targets that favor the deposition of films with a low roughness, which is a key feature for their integration in structures for optoelectronic applications. The influence of the addition of ZnO nanoparticles (~20 nm in size) or CuO nanoparticles (~5 nm in size) in the ZnPc:TPyP mixture and the impact of the added metal oxide amount on the properties of the obtained composite films were evaluated in comparison to a reference layer based only on an organic blend. Thus, in the case of nanocomposite films, the vibrational fingerprints of both organic compounds were identified in the infrared spectra, their specific strong absorption bands were observed in the UV-Vis spectra, and a quenching of the TPyP emission band was visible in the photoluminescence spectra. The morphological analysis evidenced agglomerated particles on the composite film surface, but their presence has no significant impact on the roughness of the MAPLE deposited layers. The current density-voltage (J-V) characteristics of the structures based on the nanocomposite films deposited by MAPLE revealed the critical role played by the layer composition and component ratio, an improvement in the electrical parameters values being achieved only for the films with a certain type and optimum amount of metal oxide nanoparticles.

The impact of molecular orientation on carrier transfer characteristics at a phthalocyanine and halide perovskite interface

We have studied the interface properties of metal phthalocyanine (MPc, M = Zn, Cu) molecules at a methylammonium lead iodide (MAPbI3) surface using density functional theory (DFT) based simulations. From the adsorption energies, the face-on orientation is found to have an order of magnitude stronger binding energy than the edge-on orientation, where CuPc binds a little stronger than ZnPc with its closer interfacial distance. Our detailed analysis of interface electronic structure suggests that the edge-on configuration possesses a large energy barrier for the hole transfer from MAPbI3 to MPc molecules. In contrast, the face-on configuration has no such barrier, facilitating the hole transfer, while at the same time the desirable alignment of the conduction band suppresses the electron-hole recombination. Therefore, the face-on configuration is clearly found to be more suitable for the photovoltaic process, in line with the experimental reports. Our work emphasizes the impact of MPc orientation upon perovskite solar cell efficiency besides other factors such as Pc thin film's mobility and morphology, and provides insightful guidance to efficient and stable hole transport layers.

Hierarchically interconnected ZnO nanowires for low-temperature-operated reducing gas sensors: experimental and DFT studies

The larger surface area and increased point contacts of hierarchically arranged ZnO nanowires (upper panel) offered more potential barriers for the gas molecule exhibiting binding strength CO < C₂H₅OH < NH₃ (lower panel) and provided excellent gas-sensing performance at 100 °C for NH₃ gas.

The influence of polar (0001) zinc oxide (ZnO) on the structure and morphology of vanadyl phthalocyanine (VOPc)

Metal oxide thin films are increasingly utilized in small molecular organic photovoltaic devices to facilitate electron transport and injection.