Cadmium Telluride Thin Films Research Articles

In-field monitoring of eight photovoltaic plants: degradation rate along seven years of continuous operation

<p class="Abstract">The results of more than seven years (October 2010-December 2017) of continuous monitoring are presented in this paper. Eight outdoor photovoltaic (PV) plants were monitored. The monitored plants use different technologies: mono-crystalline silicon (m-Si), poli-crystalline silicon (p-Si), string ribbon silicon, copper indium gallium selenide (CIGS), thin film, and cadmium telluride (CdTe) thin film. The thin-film and m-Si modules are used both in fixed installations and on x-y tracking systems. The results are expressed in terms of the degradation rate of the efficiency of each PV plant, which is estimated using the measurements provided by a multi-channel data acquisition system that senses both electrical and environmental quantities. A comparison with the electrical characterization of each plant obtained by means of the transient charge of a capacitive load is also made. In addition, three of the monitored plants are characterized at module level, and the estimated degradation rates are compared to the values obtained with the monitoring system. The main outcome of this work can be summarized as the higher degradation rate of thin-film based PV modules with respect to silicon-based PV modules.</p>

EMI protection elements on cadmium telluride thin films

The amplitude-time characteristics of cadmium telluride thin films switching were investigated at the influence of single impulses duration 1 μs. It has been founded that with an increase of cadmium telluride layer thickness from 3 μm up to 8 μm, an increase of the operating threshold from 70 V to 105 V is es-tablished. The maximum residual sample voltage was change in the range from 12 V to 40 V, the minimum - from 5 V to 20 V. Samples switching time was no more than 2 nanoseconds; the samples interelectrode capacity does not exceed 2 pF. All test samples were operated without failure up to 20 times. Based on the results of cadmium telluride films structural studies by X-ray diffractometry and scanning electron microscopy we proposed a mechanism of cadmium telluride films with columnar structure monostable switching based on the formation of melted high-conductivity channels in cadmium tel-luride grains oriented in the [111] direction.

Substrate temperature dependent variation in the properties of cadmium telluride thin films deposited on glass

The present study relates to the variation in properties of cadmium telluride (CdTe) thin films deposited via electron beam and thermal vacuum evaporation methods at two different substrate temperatures. The influence of substrate temperature on structural, morphological, optical and electrical properties of CdTe thin films is investigated. For structural characterization, grazing incidence X-ray diffraction technique is used which revealed that thin films deposited at 200 °C temperature are more crystalline in nature as compare to the room temperature. The parameters such as average crystallite size (D), lattice strain (e), number of crystallites per unit area (N) and texture coefficient TC (hkl) were calculated for both types of synthesized CdTe thin films. Surface morphology of thin films was recorded using scanning electron microscopy and found to be homogeneous in nature. The optical studies carried out using UV–Visible Spectrophotometer and Photoluminescence shown a decrease in band gap values for both electron beam and thermally deposited thin films samples at 200 °C substrate temperature. Electrical measurements recorded using two probes method showed the maximum value of current for CdTe thin films deposited by electron beam evaporation method at 200 °C substrate temperature.

Comparative Performance Analysis of Grid-Connected PV Power Systems with Different PV Technologies in the Hot Summer and Cold Winter Zone

The objective of this paper is to establish the performance of 8 kWp grid-connected photovoltaic (PV) power systems based on different PV module technologies in Nanjing, China. Nanjing has a hot summer and a cold winter which are considered based on monthly average solar irradiation and ambient temperature specifically for the deployment of grid-connected PV systems. The study focuses on performance assessment of grid-connected PV systems using typical PV modules made of monocrystalline silicon (m-Si), polycrystalline silicon (p-Si), edge-defined film-fed growth silicon (EFG-Si), cadmium telluride (CdTe) thin film, copper indium selenide (CIS) thin film, heterojunction with intrinsic thin layer (HIT), and hydrogenated amorphous silicon single-junction (a-Si:H single-PV) installed on location. The yearly average energy output, PV module and system efficiency, array yield, final yield, reference yield, performance ratio, monthly average array capture losses, and system losses of seven PV module technologies are all analyzed. The results show that grid-connected PV power system performance depends on geographical location, PV module types, and climate conditions such as solar radiation and ambient temperature. In addition, based on energy output and efficiency, the HIT PV power technology can be considered as the best option and CdTe and p-Si as the least suitable options for this area. The monthly average performance ratio of the CdTe technology was higher than those of other technologies over the monitoring period in Nanjing.

Effect of $$\hbox {Ar}^{+}$$ Ar + ion implantation on the properties of electrodeposited CdTe thin films

Semiconducting nanomaterials of II–VI groups are the key elements of continued technological approaches made in the field of optoelectronic, magnetic and photonic devices due to their size-dependent properties. Ion beams create changes in the material along their track; this not only exhibits excellent properties but also tailors new materials. This article reports the effect of \(\hbox {Ar}^{+}\) ion implantation on the properties of cadmium telluride thin films of about 80 nm thickness. The implantation parameters were adjusted based on computer-aided learning using SRIM (stopping and range of ions in matter) software. The CdTe thin films were deposited by electrodeposition method on ITO substrate. Thin films of CdTe are exposed to \(\hbox {Ar}^{+}\) ions with different fluencies of \(1 \times 10^{15}\), \(5 \times 10^{15}\) and \(1 \times 10^{16} \, \hbox {ions cm}^{-2}\) at Ion Beam Centre, Kurukshetra University, Kurukshetra, India. After implantation, the films were characterized using UV–visible spectroscopy, photoluminescence (PL) and a four-probe set-up with a programmable current–voltage (I–V) source metre. The scanning electron microscopy of pristine film showed smooth and uniform growth of sphere-shaped grains on substrate surface. From optical studies, the values of optical band gap for as-deposited and argon-ion-implanted thin films were calculated. It was found that values of optical band gap decreased with the increase in fluence of ion beam. From PL studies it was found that the intensity got increased with ion fluence. A considerable increase in current was noticed from I–V measurements with ion fluence after implantation. Different properties of pre- and post-implanted thin films are studied.

Structural and optical properties of cadmium telluride obtained by physical vapor deposition technique

The structural and optical properties of cadmium telluride (CdTe) thin films prepared by thermal evaporation using physical vapor deposition technique and obtained under different process conditions (different deposition time) were investigated. CdTe thin films were obtained on (100) silicon and glass substrates. The analysis of atomic force microscopy images of surface revealed a certain periodicity of the objects’ location on the surface. After detailed analysis by autocorrelation functions, it has been established that the films have a clearly expressed periodicity along the axis OX, which is due to the orientation of growth on (100) Si substrate. The optical properties indicate a smooth film with nanoparticle size (25–28) nm on surface for both thin and thick films of CdTe. The optical transparency is observed in the short infrared radiation. An analysis of the optical properties was performed using the Swanepoel method. Hence, the basic properties of the films such as refractive index, film thickness, absorption coefficient and optical conductivity are determined. The optical transparency is observed in the short infrared radiation.

Quasi-Chemistry of Intrinsic Point Defects in Cadmium Telluride Thin Films

The defect formation in cadmium telluride thin films when growing from the vapor phase by a hot-wall epitaxy method has been described with the help of quasi-chemical reactions. The analytical expressions of the dependences of concentration of free charge carriers and dominant intrinsic atomic defects on the technological factors (substrate temperature тS, evaporation temperature тE and partial vapor pressure of cadmium ) have been obtained. It has been shown that the concentration of free charge carriers in CdTe films is determined by vacancies of cadmium and tellurium.

Investigation of the Optical and Electrical Properties of Copper Telluride and Cadmium Telluride Thin Films Using Electrodeposition Technique

Investigation of the Optical and Electrical Properties of Copper Telluride and Cadmium Telluride Thin Films Using Electrodeposition Technique

A short review of CdTe and CdSe films: growth and characterization

Cadmium based thin films including CdTe and CdSe show great potential for the use in the field of solar cells, optoelectronic and biomedical applications. This work gives a brief review of the preparation of CdSe, and CdTe films by using various deposition techniques. The chemical bath deposition method was used to deposit CdSe films using three precursors such as cadmium nitrate, cadmium sulfate and cadmium acetate are reported. Also, this article reviews on the experimental advances in electrodeposited of CdSe and screen printed cadmium telluride thin films. Various characterization techniques namely, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM), UV-Visible spectrophotometer (UV-Vis) were used in the present research work have been discussed.

A comparative study on thermally and laser annealed copper and silver doped CdTe thin film solar cells

Copper (Cu) and silver (Ag) are the potential dopants that could enhance p-type doping of polycrystalline cadmium telluride (CdTe) thin films to be used in CdTe based solar cells. In this work, the effect of doping concentration of Ag and Cu in both thermal and laser anneal process of doping to CdTe thin film solar cells’ electrical performance were investigated. CdTe thin films of 3 µm thickness were deposited using the close-spaced sublimation (CSS) process and subjected to Cu and Ag doping process through dip coating in copper (II) chloride (CuCl2) and silver nitrate (AgNO3) solution, respectively at different concentration range followed by either thermal or laser annealing. Thermally annealed CdTe thin films were treated in convection oven, whereas laser annealing was carried out by illuminating the samples with pulsed neodymium-doped yttrium aluminium garnet (Nd:YAG) laser at wavelength of 532 nm. Fabricated solar cells were electrically characterized by light current-voltage (J-V) and capacitance-voltage (C-V) measurements. J-V measurement demonstrates that Cu doped CdTe solar cells are having better electrical performance as compared to Ag doped ones. The effect of increasing dopant solution concentrations seems to have consistent trend with the increase of J-V parameters as identified in this work. C-V measurement shows that Cu doped CdTe films has higher doping capability with the highest acceptor concentration of 1.5 × 1014 cm−3 compared to Ag doped CdTe films of 8.1 × 1013 cm−3. In addition, laser annealing finds lower J-V performance and acceptor concentration of Cu and Ag doped CdTe solar cells with limitations in smaller process space for surface annealing as well as optimization.

Influence of sputtering power on structural, optical and electrical properties of CdTe thin films prepared by DC magnetron sputtering

The cadmium telluride (CdTe) thin films have been successfully deposited on glass substrates by direct-current (DC) magnetron sputtering method, and the structural, optical and electrical properties of samples were investigated in this paper. X-ray diffraction patterns revealed that all samples exhibited a preferred orientation along (111) plane with cubic phase, and the crystallite size was first increased from 13.6 to 42 nm and then decreased to 31 nm as the sputtering power increased from 10 to 80 W. AFM images showed that surface morphology of CdTe films was affected by the sputtering power and the particles in the films exhibited uniform distribution with obvious RMS roughness (25.9 nm) as the sputtering power was 40 W. Meanwhile, CdTe films appeared a higher transmission properties in the range of 850–1000 nm, and the band gap of films gradually decreased from 1.96 to 1.51 eV and then increased to 1.67 eV as the sputtering power constantly increased. Raman spectrum revealed that the peak at 140 cm−1 exhibited dominant among other peaks, associated to the E mode of Te. The current–voltage (I–V) curves indicated that the conductivity of CdTe films was strongly dependent on the sputtering power and the optimal electrical properties could be achieved at the sputtering power of 40 W.

Daily Harvested Energy of Cadmium Telluride Thin Film Photovoltaic

The power generated by solar photovoltaic (PV) is highly affected by the weather environment. Thin-Film solar module of cadmium telluride (CdTe) is one of the Semi-transparent PV (STPV) that can be employed in a wide application range as a means to sunlight permeability while supplying solar electrical energy with some shading which also preferable in hot areas. The system behavior and the forecast of a STPV harvested energy requires an accurate and reliable discribtion for the power pattern rate during the day time. This research presents a real-time daily measurements for CdTe PV modules that serve the system design, prediction, and modeling. Multilayer and single installation categories are configured to be experimentally tested at different weather conditions (temperature and irradiance). The measurements were conducted at UPM University, Serdang, Malaysia, where a 6 different modules are expreinced. A wireless monitoring system with high sampling frequency employed for this purose. The results show an efficiency of 2.51 as a maximum in cloudy day conditions, while the harvested daily energy show that a multi-layer configuration may only be effective when the transparency is high. This new generation of PV module is similar to that for Silicon-based PV but it has threshold value to start power generating and promises for efficient sustainable building materials

All spray pyrolysis-coated CdTe\u2013TiO2 heterogeneous films for photo-electrochemical solar cells

Cadmium telluride (CdTe) thin films of different thicknesses deposited onto titanium dioxide (TiO2) nanoparticle layer by spray pyrolysis deposition (SPD) are demonstrated as major photo-active semiconductor in photo-electrochemical solar cell configuration using iodide/triiodide (I−/I3−) redox couple as a hole transport layer. The CdTe–TiO2 heterogeneous films were characterized by X-ray photoelectron spectroscopy which identified doublet split of Cd 3d and Ti 2p which confirms CdTe and TiO2. Optical absorbance and transmittance of CdTe and TiO2 films which were examined by UV–Vis spectroscopy confirm that the optical bandgap of CdTe is 1.5 eV with a dominant photo-absorption in the spectral window of 350–800 nm, while TiO2 showed a bandgap of 3.1 eV and is optically transparent in the visible spectral window. The present work examined photo-anodes comprising 1, 3, 5, and 10 SPD cycles of CdTe coated on TiO2 nanoparticle layer. The solar cell with 5 SPD cycles of CdTe resulting in 0.4% efficiency. Results can be articulated to the CdTe deposited by 5 SPD cycles provided an optimum surface coverage in the bulk of TiO2, while the higher SPD cycles leads to agglomeration which blocks the porosity of the heterogeneous films.

How First Solar recycles its CdTe panels

Many companies produce photovoltaic modules, but First Solar is the only one in the world that has an end-to-end recycling process. The company started selling modules in 2002 and now has about 5% of the solar market. Instead of crystalline silicon, First Solar’s photovoltaics are based on a thin-film cadmium telluride semiconductor. The firm’s recycling process, which started up in 2005, runs alongside manufacturing at its facilities in the U.S. and Malaysia. First Solar has a stand-alone recycling facility in Germany and plans to include recycling at a plant it is building in Vietnam. Customers can choose whether to have the company reclaim their old modules—and most do. “As long as we keep bringing the cost down we will keep getting the material,” says Sukhwant Raju, First Solar’s global recycling director. First Solar reclaims and reuses 90% of the panels’ semiconductor material, Raju says. “We have been very focused right

Thermal modeling and experimental evaluation of five different photovoltaic modules integrated on prototype test cells with and without water flow

An analytical model of temperature dependent electrical and thermal efficiency of mono-crystalline (m-Si), polycrystalline (p-Si), amorphous silicon thin film (a-Si), cadmium telluride thin film (CdTe) and copper indium gallium selenide (CIGS) photovoltaic modules integrated on five prototypes identical insulted test cells is developed with and without surface water flow. This model helps in ascertaining the influence of temperature on their performance of building integrated photovoltaic-thermal (BiPVT) system. The theoretically calculated results are experimentally validated in outdoor ambient environment. The electrical & thermal efficiencies are calculated for both high and low mass flow rate of water, ṁw. Daily average electrical efficiency of photovoltaic modules; m-Si, p-Si, a-Si, CdTe and CIGS with and without water flow are found to be 12.30%, 10.98%, 6.08%, 6.60% and 7.71%, and 11.41%, 10.30%, 5.86%, 6.26% and 6.99% respectively. In constant room temperature mode, variation in mass flow rate of water, ṁw is also evaluated. Overall thermal efficiency and overall exergy for all photovoltaic modules in both cases are also calculated. The characteristic equations of photovoltaic modules integrated on test cells are also developed for both cases.

Effect of CdCl2 heat treatment in (Ar + O2) atmosphere on structural and optical properties of CdTe thin films

Cadmium telluride (CdTe) thin films were deposited by thermal evaporation method under base pressure 2 × 10−5 mbar on corning glass substrate. In this work, we study the effect of cadmium chloride (CdCl2) heat treatment in argon and oxygen (Ar + O2) atmosphere on the structural, morphological and optical properties of CdTe thin films to achieve high quality thin film absorber layer for solar cells applications. The structural characteristics were studied by X-ray diffraction (XRD). The microstructure parameters of the films such as average grain size (Davg), average lattice strain (εavg) and dislocation density (ρD) have been calculated via XRD line broadening analysis. XRD investigation revealed that, the samples show polycrystalline nature pronounced with cubic zinc blende structure with a strong preferentially (1 1 1) texture orientation. It has been found that the crystallinity of the films enhanced during (Ar + O2) annealing and CdCl2 heat treatment. The surface morphology of CdTe thin films was investigated by field emission scanning electron microscope (FE-SEM). XRD and FE-SEM results of CdCl2 treated films showed recrystallization and progressive increase in grain size. The optical properties of all samples were estimated using UV–vis–near-infrared (NIR) spectrophotometer. The Swanepoel envelope method has been employed to evaluate the various optical parameters of CdTe films such as refractive index and film thickness. The as-deposited films have a relatively high value of refractive index of 2.54, in contrast the CdCl2 treated films have a relatively low value of 2.1 in the whole wavelength range. The optical energy gap values slightly decrease from 1.56 eV for as-deposited films up to 1.54 eV for CdCl2 heat treated films. CdCl2 heat treatment in (Ar + O2) atmosphere is found to be a promising method to improve the physical properties of CdTe thin film solar cells.

Amplitude-time Characteristics of Switching in Thin Films of Cadmium Telluride

Amplitude-time Characteristics of Switching in Thin Films of Cadmium Telluride

Structural and optical properties of pulsed laser deposited cadmium telluride thin films

Cadmium telluride thin (< 1 μ) films were grown by pulsed laser deposition method on glass substrates from room temperature up to 300°C. The structural and optical properties were analyzed as a function of substrate temperature and laser radiation intensity.

How to control the stoichiometry of cadmium telluride thin film for photovoltaic applications

In this study, Bube's growth model for a cadmium telluride (CdTe) polycrystalline thin film was re-examined with a view of avoiding his assumptions that neglect the vapor pressures of Cd and Te2 near the film. We proposed a new thermodynamic growth model based on the fact that there is an experimentally verified characteristic ratio (α) of equilibrium partial pressures PCd/2PTe2 that depends on the temperature T and CdTe stoichiometry. By writing PCd(0)=2α(0)PTe2(0) and PCd(h)=2α(h)PTe2(h), where α(0) is determined by source stoichiometry, we can solve the equations for α(h) and thereby determine the stoichiometry of the CdTe thin film grown under physical vapor deposition (PVD) conditions. Simulation was performed to predict the stoichiometry of the CdTe thin film as a function of source stoichiometry for various source-film temperature combinations. The results show that for a typical CdTe PVD process with Tsource&amp;gt;Tthin film: (1) stable deposition, without a non-stoichiometric composition shift, can be achieved at congruent-growth stoichiometry; (2) any stoichiometric deviation from the congruent sublimation point becomes more substantial (in the same direction) in the thin film than in the source; and (3) larger ΔT between the source and the thin film results in a more composition shift.

Review of Maximum Power Point Tracking Control of Photovoltaic Systems in Case of Uniform &amp; Non-uniform Irradiance Conditions

It is crucial to improve the photovoltaic (PV) system efficiency and to develop the reliability of PV generation control systems. One of the approaches to increase the efficiency of PV power generation system is to operate the PV systems optimally at the maximum power point. However, the PV system can be optimally operated only at a specific output voltage; otherwise the output power fluctuates under intermittent weather conditions. In addition, it is very difficult to test the performance of PV systems controller under the same weather condition during the development process where the field testing is costly and time consuming. For these reasons, the presentation is about the state of the art techniques to track the maximum available output power of photovoltaic systems called maximum power point tracking (MPPT) control systems. This topic could be also one of the most challenges in photovoltaic systems application that has been receiving much more attention worldwide. The talks will cover the application of intelligent techniques by means the artificial neural network (ANN) and fuzzy logic controller scheme using polar information to develop a novel real-time simulation technique for MPPT control by using dSPACE real-time interface system. In this case, the three-layer feed-forward ANN is trained once for different scenarios to determine the global MPP voltage and power and the fuzzy logic with polar information controller takes the global maximum power point (MPP) voltage as a reference voltage to generate the required control signal for the power converter. This type of fuzzy logic rules is implemented for the first time in MPPT control application. The proposed method has been tested using different solar cell technologies such as monocrystalline silicon, thin-film cadmium telluride and triple junction amorphous silicon solar cells. The verification of availability and stability of the proposed system through the real-time simulator shows that the proposed system can respond accurately for different scenarios and different solar cell technologies. In other cases, one of the main causes of reducing energy yield of photovoltaic systems is the partially shaded condition. Although the conventional MPPT control algorithms operate well in a uniform solar irradiance, they do not operate well in non-uniform solar irradiance conditions. The non-uniform conditions cause multiple local maximum power points on the power-voltage curve. The conventional MPPT methods cannot distinguish between the global and local peaks. Since the global power point may change within a large voltage window and also its position depends on shading patterns, it is very difficult to recognize the global operating point under partially shaded conditions. From these reasons, the presentation will address the effectiveness of the proposed MPPT method to solve the partially shaded conditions under the experimental real-time simulation technique based dSPACE real-time interface system for different size of PV arrays, such as 3x3(0.5kW) and 20x3(3.3kW) and different interconnected PV arrays, for instance series-parallel (SP), bridge link (BL) and total cross tied (TCT) configurations.