Computational design of some TTF-substituted acene-based dyes for solar cell application using hollow ZnO quantum dot as acceptor

Investigation of the Effect of Substituents on Electronic and Charge Transport Properties of Benzothiazole Derivatives

A series of new benzothiazole-derived donor-acceptor-based compounds (Comp1-4) were synthesized and characterized with the objective of tuning their multifunctional properties, i.e., charge transport, electronic, and optical. All the proposed structural formulations (Comp1-4) were commensurate using FTIR, ¹H NMR, ¹³C NMR, ESI-mass, UV-vis, and elemental analysis techniques. The effects of the electron-donating group (-CH₃) and electron-withdrawing group (-NO₂) on the optoelectronic and charge transfer properties were studied. The substituent effect on absorption was calculated at the TD-B3LYP/6-31+G** level in the gas and solvent phases. The effect of solvent polarity on the absorption spectra using various polar and nonpolar solvents, i.e., ethanol, acetone, DMF, and DMSO was investigated. Light was shed on the charge transport in benzothiazole compounds by calculating electron affinity, ionization potential, and reorganization energies. Furthermore, the synthesized compounds were used to prepare thin films on the FTO substrate to evaluate the charge carrier mobility and other related device parameters with the help of I-V characteristic measurements.

Microwave-Assisted Synthesis of Bi2S3 and Sb2S3 Nanoparticles and Their Photoelectrochemical Properties

Bi₂S₃ and Sb₂S₃ nanoparticles were prepared by microwave irradiation of single-source precursor complexes in the presence of ethylene glycol as a coordinating solvent. The as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX), photoluminescence (PL), and UV-vis near-infrared (NIR) spectroscopy. Their electrochemical potential was examined in [Fe(CN)]^4-/[Fe(CN)]^3- by cyclic and square wave voltammetry (CV and SWV) and electrochemical impedance spectroscopy (EIS). GCEBi₂S₃ and GCESb₂S₃ exhibit promising electrochemical performance and a higher specific capacitance of about 700-800 F/g in [Fe(CN)]^4-/[Fe(CN)]³. Thin films of Bi₂S₃ and Sb₂S₃ were successfully incorporated in the fabrication of solar cell devices. The fabricated device using Bi₂S₃ (under 100 mW/cm²) showed a power conversion efficiency (PCE) of 0.39%, with a V _oc of 0.96 V, a J _sc of 0.00228 mA/cm², and an FF of 44%. In addition, the device exhibits nonlinear current density-voltage characteristics, indicating that Bi₂S₃ was experiencing a Schottky contact. The Sb₂S₃-based solar cell device showed no connection in the dark and under illumination. Therefore, no efficiency was recorded for the device using Sb₂S₃, which indicated the ohmic nature of the film. This might be due to the current leakage caused by poor coverage. The nanoparticles were found to induce similar responses to the conventional semiconductor nanomaterials in relation to photoelectrochemistry. The present study indicates that Bi₂S₃ and Sb₂S₃ nanoparticles are promising semiconductor materials for developing optoelectronic and electrochemical devices as the films experience Schottky and Ohmic contacts.

A molecular device providing a remarkable spin filtering effect due to the central molecular stretch caused by lateral zigzag graphene nanoribbon electrodes

Through the density functional theory, we studied molecular devices composed of single tetrathiafulvalene (TTF) molecules connected with zigzag graphene nanoribbon electrodes by four different junctions. Interestingly, some devices have exhibited half-metallic behavior and can bring out a perfect spin filtering effect and remarkable negative differential resistance behavior. The current-voltage characteristics show that these four devices possess different spin current values. We found that all the TTF molecules were stretched due to interactions with the electrodes in the four devices. This leads to the Fermi levels of the three devices being down-shifted to the valence band; therefore, these devices exhibit half-metallic properties. The underlying mechanisms of the different spin current values are attributed to the different electron transmission pathways (via chemical bonds or through hopping between atoms). These results suggest that the device properties and conductance are controlled by different junctions. Our work predicts an effective way for designing high-performance spin-injected molecular devices.