This work focuses on preparing TiO2, CdS, and composite TiO2:CdS thin films for photovoltaic applications by thermal evaporation. The suggested materials exhibit very good optical and electrical properties and can play a significant role in enhancing the efficiency of the device. Various microscopy and spectroscopy techniques were considered to investigate the optical, morphological, photoluminescence, and electrical properties. FTIR confirms the material identification by displaying some peaks in the fingerprint region. UV Vis spectroscopy yields high transmission (80–90%) and low absorbance (5–10%) within the spectral region from 500 nm to 800 nm for the composite thin films. The optical band gap values for CdS, TiO2, and TiO2:CdS thin films are 2.42 eV, 3.72 eV, and 3.6 eV. XRD was utilized to analyze the amorphous nature of the thin films, while optical and SEM microscopy were employed to examine the morphological changes caused by the addition of CdS to TiO2. The decrease in the bandgap of the composite thin films was determined by the Tauc plot, which is endorsed due to the band tailing effects. Photoluminescence spectroscopy depicts several emission peaks in the visible region when they are excited at different wavelengths, and the electrical measurement enhances the material conductivity. Furthermore, the proposed electron transport materials (TiO2, CdS, TiO2:CdS) were simulated with different perovskite materials to validate their design by employing the SCAPS-1D program and assess their performance in commercial implementation. The observed results suggest that TiO2:CdS is a promising candidate to be used as an ETM in PSC with enhanced productivity.
Lead-free perovskite solar cells (PSCs) have sparked considerable interest in the optoelectronics research community and gained recognition in recent years due to their practical use in solar energy. The primary obstacles in producing PSCs are stability and toxicity due to the immersion of organic-cation and lead in perovskite material. This study presents an electrical simulation of a caesium–indium-based lead-free hybrid PSC using SCAPS-1D software. Spiro-MeOTAD is a typical hole transport material (HTM) used in PSC, although it has not always been suggested because of its high design cost and stability constraints. This study aims to evaluate the performance of lead-free double perovskite material as an absorber layer along with different hole transport materials (HTM). We discovered that the lead-free double perovskite combined with graphene-oxide (GO) and reduced graphene oxide (rGO) produces the best results. Furthermore, the light-harvesting layer and HTM layer has optimized via thickness, defects, doping concentration, and temperature. The improved PSC structure achieves power conversion efficiency (PCE) of more than 24%, and the results of the optimized PSC have compared to the results of the experimentally implemented PSC. This work also used C–V measurements on the optimized structure to determine the device contact potential and doping concentration. The optimized results suggest a feasible future route for creating lead-free PSC with high productivity and free from stability or toxicity issues.
Chromium doped aluminum nitride (AlN: Cr) thin films were grown on silicon, glass and copper substrates by DC and RF magnetron sputtering co-deposition. After growth, thin films on silicon substrates were annealed at 1373 K for 30 min in N2 atmosphere. The AlN: Cr thin films were characterized by x-ray diffraction for structural analysis, by FS5 spectrofluorometer for the study of photoluminescence, absorption, transmission, and chromaticity. As-deposited and annealed silicon substrate and as-deposited glass substrate thin films of AlN: Cr exhibited intense photoluminescence emission in the range of 400 to 679.5 nm. Spectral evidence demonstrated conclusively that the AlN: Cr thin films on as-deposited glass substrate and annealed silicon substrate have excellent photoluminescence emission which is due to both AlN (host) and Cr3+ ions. The reasons of photoluminescence of AlN in the visible region are surface defects and impurities. Impurities become the cause to produce different types of defects and vacancies just like oxygen point defects (O+N), nitrogen vacancies (VN) and various defect complexes (V3-Al – 3 O+N). It may also be due to the recombination of photogenerated hole with the electron occupied by the nitrogen vacancies and due to the transition between deep level of (V3-Al – 3 O+N) defect complexes and shallow level of VN and the reason behind the photoluminescence of Cr3+ ions is due to vibrational energy levels 4T1 and 4T2 and due to 4T1→4A2 and 4T2→4A2 transitions. AlN: Cr thin films can give better results in the applications like light emitting diodes (LEDs), laser diodes (LDs), field emission displays, microelectromechanical system (MEMS), optical MEMS and biomedical applications. Key words: III-V Semiconductor Material, Thin films, Photoluminescence Mechanism
In this research study, aluminum Nitride (AlN) thin film co-doped with erbium and ytterbium has been deposited on Si (100) substrate by RF magnetron Sputtering. After deposition, the film was annealed at 1100 °C in ambient conditions. It’s structural properties were investigated X-ray diffraction (XRD). Thin films morphology is studied using SEM, and EDX provides the chemical composition information. The photoluminescence property of deposited film was investigated by FS5 spectrofluorometer. XRD result revealed that the film has grown along the c-axis oriented in hexagonal wurtzite structure. SEM Result shows that the average size of the particle is 100 nm. The up-conversion luminescence showed intense green and red emission peaks at 530 nm, 552 nm, and 665 nm due to the transition of Er (2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2) with excitation of 984 nm. The excitation wavelength with 483 nm photons produces visible luminescence in the green and red region with 557 and 660 nm due to Erbium.
Aluminum nitride (AlN) is a semiconductor material possessing a hexagonal wurtzite crystal structure with a large band gap of 6.2 eV. AlN thin films have several potential applications and areas for study, particularly in optoelectronics. This research study focused on the preparation of Ni-doped AlN thin films by using DC and RF magnetron sputtering for optoelectronic applications. Additionally, a comparative analysis was also carried out on the as-deposited and annealed thin films. Several spectroscopy and microscopy techniques were considered for the characterization of structural (X-ray diffraction), morphological (SEM), chemical bonding (FTIR), and emission (PL spectroscopy) properties. The XRD results show that the thin films have an oriented c-axis hexagonal structure. SEM analysis validated the granular-like morphology of the deposited sample, and FTIR results confirm the presence of chemical bonding in deposited thin films. The photoluminescence (PL) emission spectra exhibit different peaks in the visible region when excited at different wavelengths. A sharp and intense photoluminescence peak was observed at 426 nm in the violet-blue region, which can be attributed to inter-band transitions due to the incorporation of Ni in AlN. Most of the peaks in the PL spectra occurred due to direct-band recombination and indirect impurity-band recombination. After annealing, the intensity of all observed peaks increases drastically due to the development of new phases, resulting in a decrease in defects and a corresponding increase in the crystallinity of the thin film. The observed structural, morphological, and photoluminescence results suggest that Ni: AlN is a promising candidate to be used in optoelectronics applications, specifically in photovoltaic devices and lasers.
Multiwall carbon nanotubes (MWCNTs) have recently attracted much attention due to their appealing properties in several domains. Multiwall carbon nanotubes (MWCNTs) were functionalized in this research study and then decorated with silver nanoparticles. Fourier transform Infrared Spectroscopy (FTIR) was used to check the successful attachment of hydroxyl (OH) and carboxyl (C=O) groups with MWCNTs. XRD analysis was used to check the crystallite size of silver nanoparticles and the decoration of silver nanoparticles on MWCNTs. Pure Carbon nanotubes (CNTs) show luminescence in an infrared region having approximately 1.3 eV absorption band. At room temperature, our hybrid material's photoluminescence (PL) spectra indicate only one peak in the UV region and many high-intensity peaks in the visible region. These PL results show the change in the band structure of Ag/MWCNTs composite compared to pure silver nanoparticles and carbon nanotubes. Therefore, it unlocks the possibilities to use this hybrid material for bio-sensing and bio-imaging devices, chemical sensing devices, optoelectronics devices, drug delivery devices, cancer cell detection, and environment detection devices.
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