Indian Journal of Pure & Applied Physics (IJPAP)

Improved Performance of Organic Light Emitting Diodes by Balanced Charge Injection

2026-01-01T14:59:52+0530

Balanced charge injection in organic light emitting diodes (OLEDs) has been investigated towards improving their efficiency and stability. Balanced charge injection was achieved through selective insertion and elimination of some charge injection and charge transport layers. Poly(ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was used as hole injecting layer (HIL) but because of its hygroscopic nature, it caused rapid degradation in device performance. Elimination of PEDOT:PSS and insertion of thin films of hole transporting N,N′-Di (1-naphthyl)-N,N′-diphenyl- (1,1′-biphenyl) 4,4′-diamine (NPD), and hole blocking bathocuproine (BCP) along with electron injecting 8-hydroxyquinolinolato lithium (Liq) layer led to balanced charge injection into light emitting tri(8-hydroxyquinolinato) aluminium (Alq3) layer that resulted in improved current efficiency (CE) of OLEDs. The reference device with PEDOT:PSS showed maximum CE of 0.4 cd/A, whereas the device with balanced charge injection exhibited much enhanced CE of 1.75 cd/A. Furthermore, after ~15 h of continuous operation, the reference device retained only ~15% of its initial CE whereas the device with
balanced charge injection retained over 80% of its initial CE, demonstrating substantially improved operational stability by balanced charge injection.

Thermal Analysis of CuO–MoS₂–TiO₂/Water Ternary Hybrid Nanofluid Flow over a Rotating Disk with Joule Heating and Viscous Dissipation

2026-01-21T09:42:35+0530

The CuO-MoS2-TiO2/water ternary hybrid nanofluid flow over a rotating disk is examined in this study with respect to its thermal and flow characteristics, considering the combined influences of a magnetic field, Hall current, thermal radiation, Joule heating, viscous dissipation, and a non-uniform heat source/sink. Along with velocity and thermal slip boundary conditions, the flow system also takes Darcy-Forchheimer drag into account. The bvp4c solver in MATLAB is used to solve the governing nonlinear partial differential equations numerically after they have been simplified using Von Kármán similarity transformations. The effects of several physical parameters on temperature and velocity profiles are investigated through a comprehensive parametric analysis. The findings show that porous resistance and magnetic fields improve thermal dispersion through Joule heating while suppressing fluid mobility. Additionally, the presence of the Hall current promotes radial fluid motion, even though it leads to a reduction in both axial and tangential velocity components. The findings reveal that the ternary hybrid nanofluid delivers superior thermal performance in comparison with both mono and hybrid nanofluids. An evaluation based on the Nusselt number shows that the heat transfer rate improves by nearly 18 to 25 % over mono nanofluids and 10 to 15 % over hybrid nanofluids when the operating conditions are kept unchanged. Furthermore,
enhancement in nanoparticle loading and thermal radiation parameters result in an additional 6 to 33 % rise in heat transfer, highlighting the effective synergistic thermal behaviour produced by the combined presence of three nanoparticles.

Structural, Dielectric, and AC Conductivity Studies of Silver-Doped Zinc Oxide/Polyvinyl Alcohol Nanocomposites

2026-01-22T14:06:09+0530

In this study, silver-doped zinc oxide nanoparticles (Ag-ZnO NPs) were synthesized via the hydrothermal method. The structural and chemical properties of the Ag-ZnO NPs were investigated using X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Surface morphology and optical characteristics were examined using field emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectroscopy. The Ag-ZnO NPs exhibit a spherical morphology with an average particle size of ~ 66.0 nm. Polyvinyl alcohol (PVA)-based nanocomposite films incorporating Ag-ZnO NPs in varying concentrations (1.0, 5.0, and 10.0 wt.%) were prepared using the solution-casting method. The influence of Ag-ZnO NPs concentration on the dielectric properties and AC conductivity of PVA was systematically investigated. The results indicate that inclusion of Ag-ZnO NPs improvesthe dielectric permittivity and loss up to a critical concentration (1.0 wt.%). Beyond this threshold limit a reduction in permittivity, dielectric loss, and AC conductivity was also observed. Polarizing optical microscopy further confirmed the optical transparency of the
nanocomposites, and its transparency is also affected by Ag-ZnO NPs.

RSOA-Based Reversible Logic Design: A Scalable Approach for Optical Gates and Multiplexers Using FRG Architecture

2026-01-07T12:03:12+0530

In this study, the design of fundamental all-optical logic circuits using reversible Fredkin gate architectures implemented with Reflective Semiconductor Optical Amplifiers (RSOAs) is proposed and investigated. A 2×1 multiplexer (MUX) forms the foundational element, from which key logic operations NOT, AND, OR, NAND, NOR, XOR and XNOR are derived. Additionally, a 4×1 MUX, half-adder and a half-subtractor circuits are constructed to demonstrate the scalability of the approach for complex combinational logic. All designs operate using Gaussian pulse inputs, and the switching dynamics of the RSOA-based circuits are analysed in detail. To evaluate the optical signal quality and performance, critical metrics including the Extinction Ratio (ER), Contrast Ratio (CR), and Relative eye opening (REOP) are calculated. The results confirm that the proposed circuits offer high-speed operation, low energy consumption, and excellent signal integrity, highlighting their potential for application in integrated photonic logic, Fiber-optic communication systems, and next
generation optical computing architectures.

Investigation of Photo Sensitive Properties of Ferroelectric Stannous Chloride Dihydrate Doped Triglycine Sulphate (SnCl2.2H2O-TGS) Crystal by Pseudo Spin Lattice Coupled Mode (PLCM) Model

2026-01-19T11:07:40+0530

A modified theoretical model based on a time, temperature dependent Green’s function formalism has been constructed by integrating the Pseudo-Spin Lattice Coupled Mode (PLCM) approach with the Ising spin framework to investigate ferroelectric characteristics in stannous chloride dihydrate doped triglycine sulphate (SnCl₂.2H2O-TGS) crystal. The formulation incorporates renormalized boundary condition for polarization, explicitly accounting for phonon anharmonicity up to the fourth order, together with coupling contributions from an externally applied electric field. This model has been utilized to analyze the second-order phase transition behaviour of SnCl₂.2H2O doped TGS, offering a detailed theoretical perspective on its ferroelectric phase stability. In addition, the work evaluates the photoactive performance parameters of the doped system, particularly emphasizing the photosensitivity figure of merit (M₁), high-current responsivity (M₂), vidicon suitability factor (M₃) and their corresponding ratios M₂/M₁, M₃/M₂ and M₃/M₁ under both bias-free and externally biased field environments. The findings underscore that higher-order anharmonic lattice interactions and polarization-field coupling significantly contribute to the tunability and enhancement of the electromechanical and optoelectronic behaviour of stannous chloride dihydrate doped triglycine sulphate (SnCl₂.2H2O-TGS) crystals, thereby demonstrating their potential for advanced ferroelectric and photosensitive device applications.

Quantum Simulation of One-Dimensional Crystal Band Structure with a Tunable Superconducting Electric Circuit

2026-01-12T11:40:53+0530

This paper presents a concept for a quantum simulator based on a superconducting qubit coupled to a readout resonator, designed to experimentally emulate the band structure of a one-dimensional crystal. The superconducting qubit, with its intrinsic periodic potential from the Josephson effect, serves as a direct analog of an electron in a periodic lattice. The Hamiltonian of the system is analyzed in two complementary regimes: the weak-coupling regime, corresponding to nearly free electrons, and the strong-coupling regime, corresponding to electrons in the tight-binding limit. We show that the system can be continuously swept between these regimes using a flux-tunable symmetric DC-SQUID to vary the effective Josephson energy. To probe the resulting band structure, we propose an experimental method based on two-tone spectroscopy, which maps the qubit's flux-dependent transition spectrum via the dispersive shift of a coupled resonator. Numerical simulations confirm the feasibility of this approach, visualizing the transition from a broad band dispersion in the weak-coupling limit to exponentially narrow bands in the strong-coupling limit. This platform demonstrates how tunable superconducting circuits can be used as versatile quantum simulators for fundamental solid-state physics phenomena.

Deconstructing Shor’s Algorithm Using Quantum Fourier Transform

2026-01-05T12:06:18+0530

Shor's algorithm proved a significant milestone in quantum computing since it promises an exponential speedup over conventional algorithms for integer factorization, a problem critical to modern cryptography systems. This work covers implementation steps of Shor’s algorithm and analyzes Quantum Fourier Transform (QFT) usage for extracting periodicity from quantum superpositions. Firstly, theoretical foundations of algorithm are illustrated concentrating on QFT construction and operation within the setting of the quantum circuit. Thereafter, each implementation step such as qubit optimization, modular exponentiation, and circuit design is discussed. Our findings validate the theoretical effectiveness of the QFT in solving the period-finding subroutine, while also highlighting the practical difficulties and scaling constraints presented by existing quantum hardware. The paper ends with a summary of possible advancements and future paths for error mitigation strategies and quantum algorithm design.

A Compact First-Order Mixed-Mode Multifunction Filter Architecture Using CFDITA

2026-01-05T12:09:34+0530

A first-order mixed-mode multifunction filter utilizing a Current Follower Differential Input Transconductance Amplifier (CFDITA) and a grounded capacitor is introduced in this paper. It can be configured to provide first-order high-pass (HP), low-pass (LP) and all-pass (AP) responses in current-mode as well as a HP response in transadmittance-mode. The filter offers advantages such as suitable impedances in both current-mode and transadmittance-mode, facilitating simple cascadability in either mode, ease of integration, minimal use of active and passive components, explicit current outputs to drive current-mode devices and the employment of a grounded capacitor that assists in parasitic absorption of the active element used. Additionally, it has a higher operating frequency (10.3 MHz), low power consumption (1.5 mW), electronic tunability of pole frequency and no need for matching passive components. A thorough analysis considering ideal, non ideal, and parasitic effects is provided. The study also examines the use of the suggested filter as a quadrature oscillator. Post-layout simulations utilizing the Cadence Virtuoso tool with a 180 nm GPDK (Generic Process Design Kit) technology have confirmed the developed circuits. The layout of CFDITA measures an area of 28.4 µm × 26.5 µm.

Performance Analysis of Empirical Models for Daily Global Solar Radiation in Jiri, Nepal

2026-01-28T09:34:54+0530

Accurate estimation of global solar radiation (GSR) is essential for solar energy system design, climate analysis, and sustainable energy planning. In mountainous countries such as Nepal, direct measurement of solar radiation is limited due to high instrumentation costs and sparse monitoring networks. As a result, empirical models based on routinely measured meteorological parameters provide a practical alternative for solar resource assessment. This study evaluates the performance of twenty empirical models for estimating daily global solar radiation in Jiri, a mid-hill region of eastern Nepal characterized by moderate altitude, frequent cloud cover, and strong monsoonal influence.
Long-term meteorological data, including sunshine duration, air temperature, and relative humidity, were used as model inputs. Extraterrestrial solar radiation and day length were calculated using standard astronomical relations, and model coefficients were derived through regression analysis. Model performance was assessed primarily using error-based statistical indicators, namely Root Mean Square Error (RMSE), Mean Bias Error (MBE), and Mean Percentage Error (MPE) and coefficient of determination (R2),which are more appropriate than correlation-based measures under complex climatic and topographic conditions.
The results show that the Modified Angstrom (new) models M14 and M15 outperform the other models, exhibiting the lowest RMSE values (3.63–3.67 MJ m⁻ ² day⁻ ¹), minimum MPE (approximately 9.2–9.4%), and negligible bias, indicating high accuracy and long-term stability. Models M17, M18, and M20 also demonstrate satisfactory performance and can be considered reliable alternatives. In contrast, simpler sunshine- or temperature-based models show relatively higher errors and reduced suitability for the Jiri region.
The average annual global solar radiation in Jiri was estimated as 15.05 MJ m⁻ ² day⁻ ¹ (approximately 4.18 kWh m⁻ ² day⁻ ¹), confirming significant solar energy potential. The findings highlight the importance of site-specific validation and support the use of multi-parameter empirical models for solar energy planning in Nepal’s mid-hill regions.

Study of Acoustical Parameters of a Cholesteric Liquid Crystal and Toluene Solutions

2026-01-30T09:50:49+0530

Acoustical parameters are the best tool to understand the molecular interaction of a solution of Cholesteric liquid crystal (CLC) and Toluene solvent. We have probed Acoustic Impedance (A), Adiabatic Compressibility ( Rao’s Constant, i.e., Molar sound velocity (R), Wada Constant, i.e., Molar compressibility (W) & Viscous relaxation time (T) of the solutions with varying Mole Fraction of Cholesteryl Acetate using an ultrasonic interferometer and Ostwald's viscometer. The measurements were made using an Ultrasonic interferometer at 1 MHz frequency. We have established that moderate molecular interactions are present in the systems.