Oxygenated CdS window layers for thin film CdTe photovoltaics by pulsed DC magnetron sputtering

Vapor transport deposition is an excellent method for preparing large area CdTe thin films with high quality and uniformity. Polycrystalline CdTe thin films were deposited by home-made vapor transport deposition system (VTD). The effects of substrate temperature on the property of CdTe film and the performance of CdTe solar cell were investigated. CdTe thin films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Vis spectrometer, and Hall Effect system. The results show that the CdTe thin films deposited by vapor transport deposition are cubic phase with a preferred orientation in (111) direction. The average grain size increases from 2 m to 6 m and the carrier concentration increases from 1.93×10 cm to 2.36×10 cm when the substrate temperature increases from 520 °C to 620 °C. This suggests that high substrate temperature can increase the carrier density significantly due to the suppressed defect recombination. The performance of CdTe thin film solar cells deposited at different substrate temperatures demonstrates that high substrate temperature (610°C) can greatly improve the efficiency, open circuit voltage and fill factor of the solar cells. But the substrate temperature higher than 610°C will reduce the spectral 142 无 机 材 料 学 报 第 31卷 response of the cells in long wavelength region, which results in the degradation of solar cell performance. The small-area CdTe thin film solar cell without back contact layer deposited at substrate temperature of 610°C obtains the best conversion efficiency of 11.2%.

Effect of different thermo-treatment at relatively low temperatures on the properties of indium‑tin-oxide thin films

Roll-over behavior in current-voltage curve introduced by an energy barrier at the front contact in thin film CdTe solar cell

In order to reduce light absorption of the n-type CdS window layer in high efficiency CdTe thin film solar cells, the window layer should be as thin as possible but enough thickness should be left to keep function of the p-n junction. However, many random shunting/shorting micropaths are unavoidably formed at the CdS/CdTe interface due to the CdS consumption up by the reaction/interdiffusion, or due to a noncontinuous coverage of CdS on transparent-conducting-oxide (TCO) thin films. These shunting/shorting paths are the main cause for the low open-circuit voltage and low efficiency of CdTe thin film solar cells. In this study, we propose to employ a noncontinuous highly resistive tin oxide (SnO2) layer between the TCO and the CdS window layer as an electronic shunting blocking layer. The experimental results demonstrated that the insertion of a noncontinuous SnO 2, which had a thickness of less than 10 nm, led to an enhancement in efficiency by 20% and an increase in open-circuit voltage ( $V_{{\rm{oc}}}$ ) by 14% compared to the one without SnO2. This study demonstrated an important design strategy for thin film solar cell fabrication to effectively reduce microshunting/shorting paths and to improve fabrication reproducibility of devices as well.

The mid-frequency (20–350 kHz) pulsed magnetron sputtering process has been reported as an enabling technology for the deposition of a wide range of commercially important coatings onto large area glass components. In this study, transparent titania (TiO2) coatings were deposited by reactive unbalanced magnetron sputtering in a Large Area rig built ‘in-house’ and designed to replicate an in-line coater. Deposition took place in continuous DC, pulsed DC (40, 100, 200 and 300 kHz) and AC (40 kHz) modes. The films were deposited under different magnetron configurations; single and dual planar magnetrons operated in conventional mode, and dual planar magnetrons operated in full-face erosion (FFE) mode. A calibration run was carried out for each setting to obtain the deposition rate. Then, a 1 µm thick coating was deposited onto float glass. During the sputtering process the substrates were reciprocated in a plane parallel with respect to the magnetron. The film properties were compared and assessed in terms of their structures, optical and mechanical properties using scanning electron microscopy (SEM), X-ray diffraction (XRD), spectrophotometry and nanoindentation testing. This paper compares the properties of TiO2 produced by DC, AC and pulsed DC magnetron sputtering using different magnetron configurations (static or FFE) and attempts to relate these properties to deposition parameters.

Structure and properties of Ti films deposited by dc magnetron sputtering, pulsed dc magnetron sputtering and cathodic arc evaporation

Hard yet tough CrN/Si3N4 multilayer coatings deposited by the combined deep oscillation magnetron sputtering and pulsed dc magnetron sputtering

Effects of sputtering power toward the Al-doped ZnO thin Film prepared by pulsed DC magnetron sputtering

Influence of deposition time in CdTe thin film properties grown by Close-Spaced Sublimation (CSS) for photovoltaic application

Interface modification of CdTe thin film solar cells by CdCl 2-activation

Charge carrier dynamics which governs the output characteristics and performance of solar cells, often depends on the fabrication protocol of these cells. In this study, we have fabricated the FTO/CdS/CdTe/Te/Al thin-film photovoltaic devices using thermal evaporation. We have deposited tellurium as an interlayer between the absorber layer (CdTe) and top-electrode (Al) for a better charge carrier collection. The thickness of this interlayer was varied (10 nm and 30 nm) to observe its effect on the final device output characteristics, and for the same purpose, the fabrication procedure, the thickness of the absorber layer and window layers (CdS) were kept constant of 500 nm and 100 nm respectively. The XRD analysis revealed that the CdS-window layer had a cubic structure while the CdTe existed in both hexagonal and cubic phases. The deposited CdS and CdTe thin-films showed a bandgap of 2.35 eV and 1.5 eV respectively. The device with interlayer thickness of 30 nm device showed a maximum open-circuit voltage (Voc) of 0.40 V and a maximum current of 25 μA whereas for the device with 10 nm thick interlayer shows a Voc of 0.45V and an output current of 6 μA This suggests that introduction of an interlayer enables efficient charge collection and the ability of the charge collection enhances when the thickness of interlayer is increased however, the Voc is marginally different probably due to presence of defects in the 30 nm-thick interlayer cells.

A new TCO/window-buffer combination is presented for use in thin film CdTe solar cells. The TCO layer is cadmium tin oxide (CTO) and the window-buffer layer is tin magnesium oxide (TMO). Zinc magnesium oxide (ZMO), previously utilized by other groups and our group, was also prepared. The layers were produced by hollow cathode sputtering and were characterized by optical and Hall effect measurements. It was found that the carrier concentration of the window (buffer) layer at a fixed Mg concentration could be controlled over a wide range. CdTe solar cells were fabricated on glass/TCO/TMO and other bilayers without use of CdS. Quantum efficiency data confirmed the greatly improved blue response of the cells.

Study of the physical property of the cadmium sulfide thin film depending on the process condition

Three sets of titanium oxide layers with different oxygen content were prepared by DC pulsed reactive magnetron sputtering. The layers were characterised by their thickness, conductivity, refractive index, band-gap and flat band potential. The photoelectric and photocatalytic activities of the layers irradiated by Xe discharge lamp were tested in NaOH and phenol water solution, respectively. Rather high activity of prepared layers was found; no expressive activity increase was, however, observed in contrary to the expectation connected with suboxide forms of TiOx.

Vanadium oxide thin films are increasingly explored for electronic, electrochemical, and energy-related applications due to their variable oxidation states and versatile physicochemical properties. This study systematically compares the effects of pulsed DC and RF magnetron sputtering techniques on the structural, morphological, and electrical characteristics of vanadium oxide films deposited on 304 AISI stainless steel substrates. High-purity vanadium target was sputtered in a controlled Ar/O2 environment. X-ray diffraction (XRD) revealed that pulsed DC sputtering favored the formation of monoclinic VO2, while RF sputtering promoted orthorhombic V2O5, indicating a phase transition driven by deposition parameters. The average crystallite size was smaller in pulsed DC films (~10.12 nm) than in RF films (~12.26 nm). X-ray photoelectron spectroscopy (XPS) showed that pulsed DC sputtering produced films with more stable V4+/V5+ ratios and controlled stoichiometry. In contrast, RF-deposited films exhibited higher oxidation states and greater surface contamination due to porosity. Fourier transform infrared (FTIR) spectra confirmed these phase distinctions by identifying vibrational modes corresponding to VO2-rich and V2O5-rich compositions. Scanning electron microscopy (SEM) revealed that pulsed DC film was thinner, denser, and smoother, while RF film was thicker with a porous nanostructure. Electrical measurements showed higher conductivity in pulsed DC films (~4.04 × 10-4 S/cm) than in RF films (~3.22 × 10-4 S/cm). These findings highlight the critical role of deposition technique in tailoring vanadium oxide thin films for advanced smart devices and energy systems.