Optimization of Different Temperature Annealed Nanostructured CdSe Thin Film for Photodetector Applications

In this report, we have discussed the performance of highly sensitive CdSe based photodetector. The CdSe thin films were prepared by thermal evaporation method on the cleaned glass substrate at room temperature. The influence of post annealing on the optical, morphological, structural and photo-electrical properties at different temperatures were investigated. The formation of polycrystalline CdSe films was confirmed from X-ray diffraction (XRD) and Raman studies. The change in surface morphology along with the average grain size of films were observed by field emission scanning electron microscopy (FESEM). The stoichiometric ratio of Cd and Se elements in the deposited films was verified from Energy dispersive X-ray spectroscopy (EDS). The change in various optical parameters like absorption coefficient (α), extinction coefficient (k), optical band gap (Eg), refractive index (n) etc. of the studied films were calculated from the UV-Visible measurement. Importantly, the band gap values were decreased and increased with different annealing temperatures. The CdSe film annealed at 300 °C showed good photo-response and the corresponding optical properties which make them suitable for photodetector applications.

Effect of Cd Substitution on Structural and Optical Properties of Zn1-xCdxSe Thin Films

In this research, Zn1-xCdxSe alloys (x from 0 to 1) were synthesized by solid-state microwave (SSM) method of producing thermally evaporated thin films. The cubic structure and the elemental ratios of the films were studied using X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The optical characterizations of the as-deposited film in terms of the energy band gap (Eg), photoluminescence (PL), and Raman shift spectra were conducted at the room temperature. The Eg values for the thin films from ZnSe to CdSe were 3.4 to 1.7 eV, respectively. The PL orange emission for ZnSe thin film at 565 nm, whereas 590 nm in the yellow region for CdSe thin film. From Raman shift spectra, the two longitudinal-optical phonon modes (1LO and 2LO) at 240, and 490 cm-1 are assigned for the ZnSe and CdSe thin films.

The Role of Deposition Temperature in the Photovoltaic Properties of RF-Sputtered CdSe Thin Films

Cadmium selenide (CdSe) thin films were grown on borosilicate glass substrates using the RF magnetron sputtering method. In this study, CdSe thin film was deposited at a deposition temperature in the range of 25 °C to 400 °C. The influence of deposition or growth temperature on the structural, morphological, and opto-electrical properties of CdSe films was investigated elaborately to achieve a good-quality window layer for solar-cell applications. The crystal structure, surface morphology, and opto-electrical characteristics of sputtered CdSe films were determined using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–Vis spectrophotometry, and Hall effect measurement, respectively. The XRD results revealed the polycrystalline nature of CdSe, with a hexagonal structure having a strong preferential orientation toward the (002) plane. As evident from the FESEM images, the average grain size and surface morphology of the films were dependent on deposition temperatures. The carrier concentration was obtained as 1014 cm−3. The band gap in the range of 1.65–1.79 eV was found. The explored results suggested that sputtered CdSe thin film deposited at 300 °C has the potential to be used as a window layer in solar cells.

Effect of Rapid Thermal Annealing on Thermal Evaporated CdSe Thin Film for Solar Cell Application

Cadmium Selenide (CdSe) thin films have been deposited on a cleaned glass substrate by thermal vacuum evaporation method under the pressure of 10-5 torr. These CdSe thin films were also kept into a quart glass tube for rapid thermal annealing at 60 and 120 second using a 500 W halogen lamp for crystalline the structure. These thin films were characterized for structural, optical and thermo-electrical properties. The optical studies have been done using UV-VIS-NIR, shows that the transition of the deposited film is found to be a direct band gap of 1.74, 1.70 and 1.67 eV for asdeposited, 60 sec and 120 sec annealed thin films respectively. It was also found that absorbance has increased and transmission decreased with increasing annealing time, the change in the extinction coefficient with energy (hν) has been also measured. The Thermoelectric power (TEP) studies confirm the n-type nature of CdSe thin films but as well as annealing time increased the hole concentration increased resultant n-nature of CdSe thin film changing toward p-type nature, the Seebeck coefficient for different annealing time at as-deposited (RT), 60 seconds and 120 seconds have observed 549, 949 and 1031 μV/K respectively. The SEM result shows that with increasing annealing time the grain size and roughness of surface are increased. X-ray diffraction (XRD) studies indicate that the film is like a cubic crystal structure with average crystalline size (D) was measured using Scherrer formula and it is 16.44 nm.