RESUMEN
Inverted perovskite solar cells (PSCs) have gained much attention due to their low hysteresis effect, easy fabrication, and good stability. In this research, an inverted perovskite solar cell ITO/PEDOT:PSS/CH3NH3PbI3/PCBM/Ag structure was simulated and optimized using SCAPS-1D version 3.3.10 software. The influence on the device of parameters, including perovskite thickness, total defect density, series and shunt resistances, and operating temperature, are discussed and analyzed. With optimized parameters, the efficiency increased from 13.47% to 18.33%. Then, a new SiOx/ITO/PEDOT:PSS/CH3NH3PbI3/PCBM/Ag device was proposed which includes a silicon-rich oxide (SiOx) layer. This material was used as the down-conversion energy material, which converts high-energy photons (ultraviolet UV light) into low-energy photons (visible light), improving the stability and absorption of the device. Finally, with SiOx, we obtained an efficiency of 22.46% in the simulation. Therefore, the device with the SiOx layer is the most suitable as it has better values for current density-voltage output and quantum efficiency than the device without SiOx.
RESUMEN
In this work, hybrid structures formed by nanostructured layers, which contain materials, such as porous silicon (PSi), carbon nanotubes (CNTs), graphene oxide (GO), and silicon-rich oxide (SRO), were studied. The PSi layers were obtained by electrochemical etching over which CNTs and GO were deposited by spin coating. In addition, SRO layers, in which silicon nanocrystals are embedded, were obtained by hot filament chemical vapor deposition (HFCVD) technique. Photoluminescence (PL) spectra were obtained from the hybrid structures with which a comparative analysis was completed among different PL ones. The SRO layers were used to confine the CNTs and GO. The main purpose of making these hybrid structures is to modulate their PL response and obtain different emission energy regions in the PL response. It was found that the PL spectra of the CNTs/SRO and GO/SRO structures exhibit a shift towards high energies compared to those obtained from the PSi layers; likewise, the PSi/CNTs/SRO and PSi/GO/SRO structures show a similar behavior. To identify the different emission mechanisms originated by PSi, GO, CNTs, and SRO, the PL spectra were deconvolved. It was found that the Psi/CNTs/SRO and Psi/GO/SRO structures exhibit a PL shift in respect to the PSi layers, for this reason, the modulation of the PL emission of the structures makes these hybrid structures promising candidates to be applied in the field of photonic and electroluminescent devices.
RESUMEN
In the present work, non-stoichiometric silicon oxide films (SiOx) deposited using a hot filament chemical vapor deposition technique at short time and simple parameters of depositions are reported. This is motivated by the numerous potential applications of SiOx films in areas such as optoelectronics. SiOx films were characterized with different spectroscopic techniques. The deposited films have interesting characteristics such as the presence of silicon nanoclusters without applying thermal annealing, in addition to a strong photoluminescence after applying thermal annealing in the vicinity of 1.5 eV, which may be attributed to the presence of small, oxidized silicon grains (less than 2 nm) or silicon nanocrystals (Si-nc). An interesting correlation was found between oxygen content, the presence of hydrogen, and the formation of defects in the material, with parameters such as the band gap and the Urbach energies. This correlation is interesting in the development of band gap engineering for this material for applications in photonic devices.
RESUMEN
In this work, we have obtained colloidal solutions of Si nanocrystals (Si-ncs), starting from free-standing porous silicon (PSi) layers. PSi layers were synthesized using a two-electrode Teflon electrochemical cell; the etching solution contained hydrogen peroxide 30%, hydrofluoric acid 40% (HF), and methanol. The anodizing current density was varied to 250 mA cm(-2), 1 A cm(-2), and 1.2 A cm(-2). Thus obtained, PSi was mechanically pulverized in a mortar agate; then, the PSi powders were poured into different solutions to get the final Si-ncs colloidal solutions. The different optical, morphological, and structural characteristics of the colloidal solutions with Si-ncs were measured and studied. These Si-ncs colloidal solutions, measured by photoluminescence (PL), revealed efficient blue-green or violet emission intensities. The results of X-ray diffraction (XRD) indicate that the colloidal solutions are mainly composed of silicon nanocrystallites. The result of UV-vis transmittance indicates that the optical bandgap energies of the colloidal solutions varied from 2.3 to 3.5 eV for colloids prepared in methanol, ethanol, and acetone. The transmission electron microscopy (TEM) images showed the size of the nanocrystals in the colloidal solutions. Fourier transform infrared spectroscopy (FTIR) spectra showed different types of chemical bonds such as Si-O-Si, Si-CH2, and SiH x , as well as some kind of defects. PACS: 61.46Df.-a; 61.43.Gt; 61.05.cp; 78.55.-m; 81.15.Gh.
RESUMEN
In this work, non-stoichiometric silicon oxide (SiO x ) films and (SiO x /SiO y ) junctions, as-grown and after further annealing, are characterized by different techniques. The SiO x films and (SiO x /SiO y ) junctions are obtained by hot filament chemical vapor deposition technique in the range of temperatures from 900°C to 1,150°C. Transmittance spectra of the SiO x films showed a wavelength shift of the absorption edge thus indicating an increase in the optical energy band gap, when the growth temperature decreases; a similar behavior is observed in the (SiO x /SiO y ) structures, which in turn indicates a decrease in the Si excess, as Fourier transform infrared spectroscopy (FTIR) reveals, so that, the film and junction composition changes with the growth temperature. The analysis of the photoluminescence (PL) results using the quantum confinement model suggests the presence of silicon nanocrystal (Si-nc) embedded in a SiO x matrix. For the case of the as-grown SiO x films, the absorption and emission properties are correlated with quantum effects in Si-nc and defects. For the case of the as-grown (SiO x /SiO y ) junctions, only the emission mechanism related to some kinds of defects was considered, but silicon nanocrystal embedded in a SiO x matrix is present. After thermal annealing, a phase separation into Si and SiO2 occurs, as the FTIR spectra illustrates, which has repercussions in the absorption and emission properties of the films and junctions, as shown by the change in the A and B band positions on the PL spectra. These results lead to good possibilities for proposed novel applications in optoelectronic devices. PACS: 61.05.-a; 68.37.Og; 61.05.cp; 78.55.-m; 68.37.Ps; 81.15.Gh.