Department of Physics
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Item Enhancement of electrochemical reversibility in Poly 3-hexylthiophene layers for flexible dynamic glass windows applications(Elsevier, 2024-06) Nair, Sindhu S.Thin films of Poly 3-hexylthiophene (P3HT) were deposited onto Indium Tin Oxide (ITO) coated glass substrates using a spin coating method and the films were vacuum annealed at different temperatures to study the effect of annealing on the electrochemical reversibility. From the absorption spectra, the variation of the optical band gap with annealing temperature was studied for different annealing temperatures. The optical band gap obtained for P3HT film deposited at room temperature (RT) was around 1.94 eV and 1.92 eV for the sample annealed at 100 °C. A cyclic voltammetry (CV) analysis showed that at certain applied redox potentials, P3HT thin films changed the colour from magenta to transparent and then back to magenta in the reverse potential. P3HT films annealed at 100 °C showed the best electrochemical reversibility among all the annealed samples. These electrically switchable electrochromic P3HT thin films can be used in flexible dynamic windows (FDWs) as smart windows for controlling the temperature and light in buildings, displays and mirror light modulators.Item Zinc based organic metal complexes for OLED applications(Elsevier, 2026-01) Nair, Sindhu S.Zinc-based organic metal complexes have emerged as promising materials for next-generation organic light-emitting diode (OLED) applications due to their unique electronic structure, environmental safety, and cost-effectiveness. Unlike traditional phosphorescent or thermally activated delayed fluorescence (TADF) emitters, Zn(II) complexes operate via ligand-centered (LC) and ligand-to-ligand charge transfer (LLCT) transitions, enabling precise color tuning without relying on heavy metals. These materials have a theoretical internal quantum efficiency cap of 25 %. Yet, they are compatible with solution-based production, thermally stable, easy synthesis, low toxicity, and relatively low-cost production, making them appealing for sustainable optoelectronic technologies. This review systematically examines Zn(II) complexes categorized by emission color, including blue, green, yellow, red, and white. It also highlights the molecular design strategies that influence their photophysical properties and device performance. We emphasize the relationship between molecular structure, electronic behavior, and OLED functionality to guide the rational design of new Zn-based emitters. These insights lay the groundwork for future research into sustainable, high-performance OLED materials, highlighting Zn(II) complexes as a promising route toward scalable, low-toxicity optoelectronic technologies.Item Fabrication of novel thin film capacitor based on PVA/ZnO nanocomposites as dielectric material(Springer, 2020-11) Nair, Sindhu S.A three-layer thin film capacitor was designed and fabricated with PVA/ZnO nanocomposite as dielectric material. Addition of ZnO nanoparticles showed change in dielectric constant, which varied with frequency and weight percentage. ZnO nanoparticles of weight percentage of 0.5% is chosen for the synthesis of nanoparticles with a grain size of 54 nm, using cost-effective and simple co-precipitation method. It is a low-cost method for large-scale production without impurities. The agglomeration was reduced by adding the starch molecules so that the O–H functional groups could hold together to the nanoparticles at the earlier nucleation stage and can be removed when purification by centrifugation is done. Fourier-transform infrared spectroscopy analysis showed peaks due to the O–H groups in the polymer backbone, CH2 asymmetric and symmetric stretching, C–C stretching and Zn–O stretching, respectively, indicating formation of the proper film. From the profilometer, the thickness was calculated as 195.73 nm for the dielectric film. The fabricated device showed capacitance of 210 nF m−2 in par with the theoretical value (254.451 nF m−2) at 298 K.Item Synthesis and Fabrication of Fluorescent Green OLEDs Based on PEDOT:PSS/Silver Nanowire Hybrid-Composite Anode and Their Performance(IOP, 2021-03) Nair, Sindhu S.Transparent conducting films have attracted increasing attention for their usefulness in optoelectronic devices, such as solar cells, liquid crystal display, and LEDs. Silver nanowires (AgNWs) with a length of 20 μm and a diameter of 70 nm was synthesized using polyol process. The optimized concentration of AgNWs is 0.5 mg of Ag NWs in 1 ml of PEDOT:PSS and it was used to fabricate PEDOT:PSS/AgNWs hybrid-composite TCF electrode, resulting in 88% transmittance and good electrical conductive (30 Ω sq−1) thin film. Two types of green fluorescent OLEDs were fabricated: those made with conventional ITO anode and the anode based on PEDOT:PSS/Ag NWs hybrid-composite. The observed maximum luminous intensity was increased by 27% in OLED fabricated PEDOT:PSS/AgNWs hybrid-composite TCF electrode, compared to the conventional ITO. At a wavelength of 530 nm, the maximum luminous intensities for green fluorescent OLEDs fabricated on PEDOT:PSS/AgNWs hybrid-composite TCF and ITO anode were 1610 counts per second and 1260 counts per second, respectively. The observed maximum current density increased by 28% as compared to the conventional ITO. The observed current densities were 370 mA cm−2 for OLEDs fabricated on PEDOT:PSS/AgNWs hybrid-composite TCF-based anode, and 293 mA cm−2 for conventional ITO anode. The proposed hybrid-composite electrode is a suitable material to replace conventional ITO.Item Two-dimensional transparent Ag/Al metal temperature sensor(IAS, 2021-01) Nair, Sindhu S.Room-temperature thermocouple with good sensing properties is getting attracted increasingly because of their low power consumption and remarkable stability. Our study is based on the design and construction of a prototype transparent temperature sensor using thermocouple. 2D temperature thin film sensor was fabricated using magnetic masking. Thermocouples were made with thin-film, which showed a steady and reproducible temperature response. A potential difference was also shown for per degree temperature change. The transparency is obtained by special type of magnetic masking for thin-film process.