Influence of zinc concentration on band gap and sub-band gap absorption on ZnO nanocrystalline thin films sol-gel grown

Abstract

ZnO thin films were fabricated on quartz substrates at different zinc acetate molar concentrations using sol-gel spin coating method. The samples were characterized using X-ray diffraction, field emission scanning electron microscope, UV-Vis spectroscopy, FT-IR spectroscopy and photoluminescence spectroscopy. Sub-band gap absorption of ZnO thin films in the forbidden energy region was carried out using highly sensitive photothermal deflection spectroscopy (PDS). The absorption coefficients of ZnO thin films increased in the range of 1.5 eV to 3.0 eV, upon increasing zinc concentration. The optical band gaps were evaluated using Tauc's plots and found to be in the range of 3.31 eV to 3.18 eV. They showed the red shift in the band edge on increase in zinc concentration. The PL spectra of ZnO thin films revealed the characteristic band edge emission centered at the 396 nm along with green emission centered at the 521 nm.

Performance analysis of WSe2-based bifacial solar cells with different electron transport and hole transport materials by SCAPS-1D

“…The reflectivity at the front and back contact are considered to be 10 % and 90 % respectively, while other properties of the front-contact, back-contact, and working temperature are provided in Table 2 . In this simulation, the experimental optical absorption coefficient of the WSe 2 , Cu 2 O:N, and different ETLs are taken from the literature [ 50 , 62 , 63 , 64 , 65 , 66 ]. The device is irradiated with a standard AM 1.5G solar spectrum at the power of 100 mW/cm 2 .…”

Effects of ZnO nanoparticles on the antifungal performance of Fe3O4/ZnO nanocomposites prepared from natural sand

“…Interestingly, the C=O functional group shifted to wavenumbers of 1359, 1403, and 1497 cm −1 for the FZ2, FZ3, and FZ4 samples, respectively. The presence of the carboxyl vibrations for the FZ2, FZ3, FZ4, and FZ5 samples was believed to be contributed by the acetate group [35] and by the CO 2 molecule in air. However, the presence of the small peaks at wavenumbers of 1408 cm −1 and 1561 cm −1 for the FZ1 sample was predicted as the effect of the adsorption of the CO 2 molecule in air [36], which occurred on the surface of the Fe 3 O 4 [37].…”

Aerosol-assisted chemical vapor deposition of MSe and MSSe thin films using zinc(ii) and cadmium(ii) single source precursors containing hybrid Se,X-PNC ligands

“…This absorption may arise due to the surface state induced by impurities. 85,90 As seen, it could be only observed in crystalline films. 91 E g values of annealed films are plotted in Fig.…”

“…The Stokes shift (Δ) was between 0.8 and 0 eV and was related to the presence of at least one deep trapping site and electron–hole recombination via trap state or imperfection site. 90,96 The FWHM values were in the range of 183.1–189.6 meV (79.6–83.4 nm), suggesting the good crystalline quality of the films, which also accounts for the very weak intensity of deep level emissions observed at lower energy and which are due to impurities (as P species) or structural defects formed during the growth process. Only 5Fb showed higher energy signals, which are often observed in the 1.60–1.78 eV range and denoted as “shallow states” peaks, some similar bands were reported in CdSe nanowires 96 and CdSSe nanobelts.…”