ABSTRACT The rapid advancement of photovoltaic technologies has intensified the demand for lightweight, low‐cost and visually seamless solar cells for next‐generation applications, including building‐integrated photovoltaics (BIPV), electric vehicles (EVs), portable electronics and semi‐transparent energy‐harvesting surfaces. Among emerging technologies, ultrathin and semitransparent perovskite solar cells have attracted significant attention due to their exceptional power conversion efficiencies, high optical tunability and compatibility with flexible and transparent substrates. This review paper critically evaluates semitransparent perovskite solar cells (ST‐PSCs) by systematically linking absorber thickness and composition, micro structured architectures, transparent electrodes, optical performance, stability and application requirements. Rather than assessing devices solely based on power conversion efficiency (PCE), the review provides a comprehensive comparison using PCE alongside average visible transmittance (AVT), light utilization efficiency (LUE), colour‐rendering index and reported stability conditions. It distinguishes between transparent, semitransparent, ultrathin and micro structured PSC architectures and explains the physical mechanisms governing the fundamental trade‐off between photovoltaic efficiency and optical transparency. Transparent electrodes are critically assessed in terms of their electrical, optical, mechanical, manufacturing and stability characteristics, whereas the specific requirements of BIPV are examined at both device and module levels. Recent experimental and theoretical advances are further reviewed to identify practical pathways towards scalable, durable and visually acceptable photovoltaic windows and other transparent energy‐harvesting surfaces.
We evaluate a hybrid visible light communication (VLC) downlink and beam-steered infrared (IR) uplink in a 5 & times; 5 & times; 3 m indoor room under line-of-sight (LOS), non-line-of-sight (NLOS) and user-mobility scenarios. A MATLAB-based framework is used to analyse bit error rate (BER), signal-to-noise ratio (SNR), spectral efficiency, received power and delay metrics. The evaluation follows classical indoor optical wireless channel models with explicitly parameterised noise, reflection and mobility assumptions to ensure reproducibility. With Turbo coding, the BER falls below once the electrical SNR exceeds 10 dB, following the theoretical BPSK-AWGN waterfall trend whilst exhibiting a clear coding gain relative to the uncoded BPSK benchmark under both LOS and NLOS conditions. VLC achieves high SNR and spectral efficiency near the room centre but degrades towards boundaries due to multipath and shadowing. The IR uplink with adaptive beam steering provides more uniform coverage and robustness in mobility and NLOS conditions. A qualitative comparison with RF systems highlights differences in spectrum availability, interference characteristics and spatial confinement. These findings confirm the feasibility of hybrid VLC-IR systems for smart-building and indoor IoT scenarios. Future extensions will explore machine-learning-based steering and integration with IEEE 802.11bb standards to support large-scale deployment.
ABSTRACT The continuous increase of data traffic demands necessitates evolution of optical communication systems towards larger capacities enabled by highly performing optical transmitters that generate multilevel and multidimensional ultrahigh data rate signals. Commercially deployed transmitters rely on high‐order electronic digital‐to‐analog converters (eDACs) that drive optical Mach–Zehnder Modulators (MZMs) under particular biasing/driving conditions. However, these conventional transmitters face bandwidth and power consumption limitations arising from the eDACs and the nonlinearity of MZMs transfer function among others. Recently, alternative transmitter architectures have been proposed to perform direct digital to optical conversion, by relying on the utilisation of lower‐order eDACs/drivers in combination with an increased number of MZMs operated with different biasing/driving conditions compared to the conventional transmitters, which are configured in either serial cascade or parallel stacking configurations. These novel transmitter architectures are referred as serial or parallel ‘Optical DACs’ (oDACs) enabling ultrahigh data rate and improved signal quality. In this article, we first discuss the issues of conventional optical transmitters and subsequently analyse selected oDAC architectures that solely rely on simple NRZ drivers or PAM4 eDACs. Simulation studies demonstrate their superior bit rate scalability (up to 3.2 Tbps) and analysis of power consumption reveals savings of about 40% comparing with conventional architectures.
ABSTRACT Free‐space optical (FSO) communication is rapidly advancing as a high‐capacity wireless technology, with growing interest in extending its operation from the traditional near‐infrared to the mid‐infrared (mid‐IR) spectral region. Particularly, the mid‐wave infrared (MWIR) and long‐wave infrared (LWIR) atmospheric transmission windows in the mid‐IR region provide advantages regarding reduced turbulence effects, scattering and absorption, enabling more robust links under adverse conditions. This review presents recent progress in MWIR and LWIR FSO communication systems, highlighting advances in transmitter and receiver technologies, such as quantum cascade lasers (QCLs), lithium niobate modulators and detectors, including quantum cascade detectors (QCDs), mercury cadmium telluride (HgCdTe and MCT) photodiodes and quantum‐well infrared photodetectors (QWIPs). Experimental demonstrations achieving multigigabit to tens‐of‐gigabit data rates with advanced modulation formats, digital equalisation and coherent detection are summarised. The paper discusses integration trends in MWIR and LWIR photonics, coherent communication strategies and hybrid FSO–radio frequency (RF) architectures. Together, these developments outline the pathway for MWIR and LWIR FSO systems to evolve from laboratory demonstrations towards scalable, practical platforms for next‐generation terrestrial and space communication networks.
ABSTRACT This paper presents a terahertz metamaterial sensor designed to detect changes in ethanol concentration in water, which is highly relevant for chemical analysis, food safety, and biomedical sensing applications. The sensor comprises three distinct layers: a graphene‐based resonator at the top, an intermediate dielectric spacer layer, and a metallic layer at the bottom, forming a compact and efficient absorber structure. The sensor exhibits an absorption of 99% at a resonant frequency of 6.08 THz for 0% ethanol concentration, with a quality (Q) factor of 31.48. Furthermore, the effects of various graphene material parameters, such as chemical potential and relaxation time, on absorption performance have been systematically investigated through numerical simulations to achieve an optimal response and enhanced sensing performance. As the ethanol concentration increases, the resonant frequency gradually shifts to lower values due to the rise in the effective refractive index near the sensing region, enabling reliable refractive index discrimination. The proposed sensor achieves a high figure of merit (FOM) of 12.4, indicating excellent resolution for refractive index detection, along with a sensitivity of 2369 GHz/RIU and a full width at half maximum (FWHM) of 190 GHz. These results demonstrate that the proposed graphene‐based terahertz sensor offers a promising platform for high‐resolution, noncontact liquid sensing in the terahertz frequency regime.
