In this paper, we report a size-controlled metal oxide under a low-temperature process for the fabrication of an electrochemical sensor based on ultra-small nickel oxide (NiO) nanoparticles (NPs) which are utilized as electrode materials for the detection of n-butylamine chemical. The small size effect (∼6 ± 0.5 nm) and richness of Ni³⁺ ion concentration of as-synthesized ultra-small NiO nanoparticles exhibited high and reproducible sensitivity of ∼9.51 mA·mM⁻¹·cm⁻², limit of detection (LOD) ∼144.21 μM and correlation coefficient (R) ∼ 0.9688 with improved linearity in the range of 100 nM−100 μM.

Metal-oxide-based electrodes play a crucial role in various transparent conductive oxide (TCO) applications. Among the p-type materials, nickel oxide is a promising electrically conductive material due to its good stability, large bandgap, and deep valence band. Here, we display pristine and 3 at.%V-doped NiO synthesized by the solvothermal decomposition method. The properties of both the pristine and 3 at.%V:NiO nanoparticles were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Raman spectroscopy, ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). The film properties were characterized by atomic force microscopy (AFM) and a source meter. Our results suggest that incorporation of vanadium into the NiO lattice significantly improves both electrical conductivity and hole extraction. Also, 3 at.%V:NiO exhibits a lower crystalline size when compared to pristine nickel oxide, which maintains the reduction of surface roughness. These results indicate that vanadium is an excellent dopant for NiO.

In this work NiO monodispersed quantum dots (QDs) were synthesized by the reduction of nickel (II) acetylacetonate with the borane–trimethylamine complex in a mixture of oleylamine, which acted as capping agent and helped to control the particle size growth. These were then used as a hole transport layer in regular (n–i–p) type organic–inorganic hybrid perovskite solar cells. Morphology of the NiO QDs was observed with Field emission electron microscope (FESEM) and high resolution transmission electron microscope (HR-TEM) that revealed a monodispersed particles of an average particle size of about 5.5 ± 0.5 nm with distinct lattice fringes (spacing of 0.24 nm). A solar cell was fabricated on FTO glass by coating compact TiO₂, methylammonium lead halide (MAPbI), NiO-QDs and gold electrode (FTO/c-TiO₂/MAPbI/NiO/Au). With the fabricated cell, we were able to obtain photo-conversion efficiency of 6.2%, fill factor of 0. 56, J _sc is 10.77 mA/cm² and V _oc is 1.02 V, which is a reasonable value for such cells.

A linear–shaped small organic molecule (E)-4-(5-(3,5-dimethoxy-styryl)thiophen-2-yl)-7-(5″-hexyl-[2,2′:5′,2″-terthiophen]-5-yl)benzo[c][1,2,5]thiadiazole (MBTR) comprising a benzothiadiazole (BTD) acceptor linked with the terminal donors bithiophene and dimethoxy vinylbenzene through a π-bridge thiophene was synthesized and analyzed. The MBTR efficiently tuned the thermal, absorption, and emission characteristics to enhance the molecular packing and aggregation behaviors in the solid state. The obtained optical bandgap of 1.86 eV and low-lying highest occupied molecular orbital (HOMO) level of −5.42 eV efficiently lowered the energy losses in the fabricated devices, thereby achieving enhanced photovoltaic performances. The optimized MBTR:PC₇₁BM (1:2.5 w/w%) fullerene-based devices showed a maximum power conversion efficiency (PCE) of 7.05%, with an open-circuit voltage (V_OC) of 0.943 V, short-circuit current density (J_SC) of 12.63 mA/cm², and fill factor (FF) of 59.2%. With the addition of 3% 1,8-diiodooctane (DIO), the PCE improved to 8.76% with a high V_OC of 1.02 V, J_SC of 13.78 mA/cm², and FF of 62.3%, which are associated with improved charge transport at the donor/acceptor interfaces owing to the fibrous active layer morphology and favorable phase separation. These results demonstrate that the introduction of suitable donor/acceptor groups in molecular design and device engineering is an effective approach to enhancing the photovoltaic performances of organic solar cells.