Dark Current-voltage Characteristics Research Articles

11.6% Efficient Textured InP Solar Cell with Nb2O5: A Cutting-Edge Electron Transport Layer Innovation

Enhancing the efficiency of solar cells depends on minimizing reflection losses to boost photon absorption. In this study, we investigated the chemical etching process of pristine InP(100), (named as pris-InP(100)). Our findings demonstrate that the etching process resulted in a self-organizing V-groove microstructure, as revealed by atomic force microscopy and scanning electron microscopy. This induced V-groove microstructure resulted a significant reduction in the reflection loss. Through temporal variation in the etching process, we identified that a 5-minute etch (named as etch5-InP(100)), yielded the lowest reflectance. Additionally, radiofrequency (RF) magnetron sputtering was employed to deposit a 10 nm Nb2O5 thin film on both pris-InP (100) and etch5-InP (100) samples. The results indicated that the thin film on etch5-InP(100) exhibited significantly lower reflectance compared to pris-InP(100). Moreover, ab-initio calculations verified the stability and presence of native oxide at the interface of the Nb2O5/InP(100) heterostructure. Furthermore, dark current-voltage (I-V) characteristics indicated typical diode behaviour for both Nb2O5 thin films deposited on pris-InP(100) and etch5-InP(100). Notably, light I-V measurements revealed that the Nb2O5 thin film on etch5-InP(100) achieved a higher efficiency of 11.6% compared to the 8.7% efficiency of pris-InP(100). This study provides valuable insights and guidelines for the development of high-efficiency InP-based solar cells.

Investigation of the Electrical Properties of Cu-doped CoOx/n-Si Structures Fabricated by the Sol-Gel Method

The sol-gel spin coating technique was employed for the deposition of thin films comprising CoOx, Cu-doped CoOx, and CuOx onto n-Si substrates. Subsequently, an exhaustive examination of the electrical properties of the resultant heterojunction structures was conducted. The outcomes unequivocally indicate that the incorporation of Cu through doping exerts a pronounced influence on the electrical attributes of the CoOx/n-Si diode. Notably, all diodes exhibit rectifying behavior, a discernible feature in their dark current-voltage (I-V) characteristics. The I-V data was further utilized to ascertain pivotal junction parameters, encompassing series resistance (Rs), rectification ratio (RR), ideality factor (n), and barrier height (ΦB). The values of the ideality factor for CoOx/n-Si, Cu doped CoOx/n-Si and CuOx/n-Si are obtained to be 3.19, 1.99 and 2.19 eV, respectively. Furthermore, the capacitance-voltage (C-V) characteristics of diodes were performed within the frequency range of 10 kHz to 1 MHz. These findings underscore that judicious manipulation of the copper doping concentration can serve as an effective means to modulate the electrical properties of CoOx/n-Si diodes.

Non-thermal atmospheric jet plasma effects on the morphological, electrical and optical properties of nanocrystalline silicon

In this study, a non-thermal atmospheric argon plasma jet (NTAPJ) was designed and used to treat the porous silicon layer, prepared by photoelectrochemical etching (PECE). The porous silicon layers were distinguished before and after the cold plasma treatment utilized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL), and dark and photo current-voltage characteristics. The results confirmed the nanostructure of the formed porous silicon. After the treatment with argon plasma, the intensity of the XRD peak increased, and the porosity decreased from 93% to 62%. Additionally, porous silicon's average roughness (Sa) and root mean square (Sq) were reduced from 60.10 to 12.31nm and 73.70 to 16.53nm, respectively. The current-voltage characteristic indicated the increase in photocurrent and the ideality factor, as well as a decrease in dynamic resistance. The photoluminescence results showed a change in PL peaks, represented by a blue shift, an increase in intensity, and a vanishing of another peak.

Non-thermal atmospheric jet plasma effects on the morphological, electrical and optical properties of nanocrystalline silicon

In this study, a non-thermal atmospheric argon plasma jet (NTAPJ) was designed and used to treat the porous silicon layer, prepared by photoelectrochemical etching (PECE). The porous silicon layers were distinguished before and after the cold plasma treatment utilized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL), and dark and photo current-voltage characteristics. The results confirmed the nanostructure of the formed porous silicon. After the treatment with argon plasma, the intensity of the XRD peak increased, and the porosity decreased from 93% to 62%. Additionally, porous silicon's average roughness (Sa) and root mean square (Sq) were reduced from 60.10 to 12.31nm and 73.70 to 16.53nm, respectively. The current-voltage characteristic indicated the increase in photocurrent and the ideality factor, as well as a decrease in dynamic resistance. The photoluminescence results showed a change in PL peaks, represented by a blue shift, an increase in intensity, and a vanishing of another peak.

Study of electrical properties of fullerene based all-small-molecule low donor organic devices with and without cathode buffer layers for photovoltaic application

This article examines electrical properties of fullerene (C70) based all-small-molecule organic photovoltaics with low donor concentration. Enhancements in the properties of devices are observed with the incorporation of lithium fluoride (LiF) and molybdenum trioxide (MoO3) as cathode buffer layers (CBLs). Samples are characterized using field emission-scanning electron microscopy (FESEM), optical absorption spectra, current-voltage (I-V) characteristics in dark and under illumination, and capacitance-frequency (C-ω) measurements. Device with single CBL (LiF) exhibits reduced photoabsorption leading to less saturation photocurrent density (Jsat) and lower maximum exciton generation rate (Gmax), due to non-uniform deposition of LiF in device. In contrast, device having two CBLs (LiF & MoO3) has enhanced the photoabsorption exhibiting high Jsat and Gmax attributed to uniform deposition of MoO3. Moreover, dielectric properties and AC conductivity of devices are also measured confirming the results and these are found to be dependent on the frequency and voltage.

Analysis of the Influence of Formation of Pd Silicides on Surface Layers of Si on the Diffusion of Atoms of Contacting Metal

4-probe measurements of surface resistivity, measurements of dark and light current-voltage characteristics, the possibilities of using a thin PdSi film to obtain perfect nano-sized ohmic contacts on the Si(111) surface have been investigated using Auger electron spectroscopy methods in combination with ion etching of the surface. It has been shown that the depth of Ni diffusion in the Ni-Si (111) system is 400 ‑ 500 Å at indoor temperature, and 70 – 80 Å in the Ni-PdSi-Si (111) system. The quality of the ohmic contact in the latter case does not change up to T = 800 K and withstands luminous flux illumination up to F = 1100 lux. It is shown that the resistivity of the PdSi film passes through a minimum at T = 900 – 1000 K. An analysis of the results obtained will be given in the article.

Ionization processes of negative corona discharge. Part 2. Theory. Comparison with experiment

The purpose of the research is a theoretical analysis of ionization processes in the air, which are initiated by a high-voltage field generated by the negative needle-flat electrode electrode system. Methods. Fe, Cu, Al electrodes are used. Calculations are carried out using the methods of quantum mechanics and mathematical physics. Results. The processes of cold and thermoelectron emission of electrons, enhanced by an external high-voltage field (Schottky emission), are analyzed. The conditions under which the generation of charges from the cathode surface due to plasma-chemical reactions and the capture of surface electrons by electronegative oxygen molecules are decisive are investigated. Based on the PE theory, a theory of injection of negative ions from the cathode into an electronegative gas is constructed and the theory is compared with experiment. It has been shown that at small radii of curvature of needle tips, when E ≥ 106 V/cm, the generation of charges is due to cold emission of electrons. In average fields E ≈ 105 V/cm, electron emission is due to the Schottky effect. In fields E ≈ 104 V/cm and below, injection is caused by electrochemical processes and PE capture. A theory has been developed for PEs that appear at electric field intensities on the electrode of the order of several tens of kV/cm, that is, on flat and slightly curved negative electrodes. The capture of PE by electron-withdrawing molecules causes an injection current and, as a consequence, the ignition of a corona discharge. Analytical expressions for the surface density as a function of the local electric field strength, as well as an expression for the injection current, are obtained. The agreement between theory and experiment is satisfactory. Conclusion. An analysis of the development of CR on negative needles is given. A theory of PE at the cathode in strong electric fields was developed. Based on the results of measuring dark negative current-voltage characteristics, it is possible to determine the patterns of surface processes involving electronic transitions, in particular, determine the concentration of PE and injection currents.

Structures, electrical properties and catecholase-like activity of a series of new copper(II) coordination polymers supported by azido bridges

A series of new copper(II)-azido complexes of 1D polymeric chains of [Cu(L1)(μ1,3-N3)]n (1) and [Cu(L2)(μ1,3-N3)]n (2), and binuclear [Cu(L3)(μ1,1-N3)]2 (3) [HL1 = N-butyl-N-(5-bromosalcylidine)ethane-1,2-diamine, HL2 = N-butyl-N-(5-chlorosalcylidine)ethane-1,2-diamine, HL3 = N-butyl-N-(salcylidine)ethane-1,2-diamine] have been synthesized and characterized. Characterizations of 1–3 have been accomplished by usual physico-chemical techniques such as elemental analysis, FTIR, UV–vis and single crystal X-ray diffraction studies. X-ray diffraction analyses of 1 and 2 reveal that the monomeric units of 1D polymers are interconnected via the μ1,3-azido bridging. The coordination geometry around the copper(II) centers in 1 and 2 can be best described as distorted square pyramidal environments. Complex 3 shows a centrosymmetric structure with two copper(II) centers that are held together by μ1,1-azido bridging in a distorted square pyramidal environment. In the electrical studies of 1–3, both direct current (dc) and alternating current (ac) analyses have been carried out based on the metal-complex (1/2/3)-metal (M-S-M) structures. The sheet resistance of the deposited films and the metal-complex contact resistance are estimated by employing transfer length method (TLM) measurements. The dark current-voltage characteristics of Al-complex (1/2/3)-Al structures are analyzed by considering dual back-to-back Schottky barrier diode structure. The voltage variations of the device current under illumination (400–700 nm) clearly demonstrate the photo-sensitivity of these materials. The catalytic activities of 1–3 have been investigated towards aerial oxidation of 3,5-di-tert-butylcatechol. All three complexes exhibit potential catalytic effectiveness towards oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butyl-o-quinone (3,5-DTBQ) with turnover numbers 14.76, 33.92 and 81.02 h−1 for 1, 2 and 3, respectively.

Monitoring and Diagnostic Method for Maintaining the Operation Parameters of a Solar Module under Non-Uniform Illumination

The most well-known methods for diagnosing solar modules are considered; it is shown that the described diagnostic methods do not allow identifying defects that develop over a long time. The operation of photovoltaic cells under non-uniform illumination is analyzed. It has been shown that the operation of solar modules under non-uniform illumination can lead to thermal damage to semiconductor materials and deterioration in the module energy characteristics due to the fact that some of the photovoltaic cells located at reduced energy illumination become a parasitic load for more illuminated photovoltaic cells included in such module. An analytical equation has been obtained in explicit form for the full current-voltage characteristic of a photovoltaic cell using the Lambert W-function in forward and reverse bias, which makes it possible to study the connections of photovoltaic cells as a part of a solar module under non-uniform energy illumination, where the reverse branch of the current-voltage characteristic is important. The analytical equation makes it possible to predict the behavior of photovoltaic cells and solar modules composed of them under various operating modes, including identifying the degradation process. An electronic measuring device has been developed and manufactured that makes it possible to measure the light and dark current-voltage characteristics of a photovoltaic cell, including the negative branch, in automatic mode. This reduces measurement time and the influence of external experimental conditions when obtaining the current-voltage characteristics of the photovoltaic cell. A method for constructing solar modules from photovoltaic cells under conditions of their operation under non-uniform lighting has been proposed. As a result of such selection, reliability is increased and an increase in the efficiency of the solar module in shading mode, composed of series-connected photovoltaic cells selected in this way, is achieved.

Charge transport, photoresponse and impedance spectroscopy for Au/NiTPP/n-Si/Al diode

The current work was illustrated the impact of a thin film from Ni (II) Tetraphenylporphyrin (NiTPP) on the performance of the Au/n-Si Schottky. Structural and topographical properties of a NiTPP/n-Si thin film were examined using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The NiTPP/n-Si film was nanocrystalline, with an average crystallite size of approximately 33.87 nm and an average roughness of around 4.30 nm. The molecular structure and purity of NiTPP/n-Si were also confirmed using Raman spectra. Dark current-voltage (I-V) characteristics were used to determine and describe the diode parameters and conduction processes at forward bias as a function of temperature (300–390 K) for an Au/NiTPP/n-Si/Al diode. Photoresponse qualities of the diode were investigated under different illumination conditions. The reverse current of the diode grows as the light intensity increases. Impedance spectroscopy (IS) was performed at 0.025–1000 kHz. To assess the interface and recombination processes, the equivalent circuit model was thoroughly investigated. The findings demonstrate that the Au/NiTPP/n-Si/Al diode as a photodetector had significant potential for using in next-generation electrical devices.

Effect of Temperature on Photovoltaic Solar Cell Cadmium Telluride Thin Film

Solar cell technology comes with unique temperature coefficients. These temperature coefficients are important and temperature of the solar cell has direct influence on the power output of a photovoltaic cells. CdTe is a very robust and chemically stable material and for this reason its related solar cell. Thin film photovoltaic technology is now the only thin film technology in the first top 10 producers in the world. The strong improvement in efficiency in the last 7 years was obtained by a new redesign of the CdTe solar cell device reaching a single solar cell. In this paper, we describe the fabrication process following the history of the solar cell as it was developed in the early years up to the latest development and changes. The configuration of fabricated cell is n-CdTe/NaOH (0.15 M) + S (0.15 M) + Na2S (0.15 M)/C(graphite). The junction ideality factor was found to be 2.63, 2.13, and 1.89. The flat band potential is found to be -0.400, -0.450, -0.501 V. The barrier height value was found to be 0.523, 0.487, and 0.436 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency were found to be 120 mV, 24.2 μA, 32.68%, 26.18%, and 19.73% and 0.63%, 0.37%, and 0.23%, respectively. The lighted ideality factor was calculated and found to be 3.26, 1.87, and 1.17. Spectra attain maximum value of current at λ = 580 nm and decrease with increase in wavelength. The photovoltaic cell characterization of the thin films is carried out by studying current-voltage characteristics in dark, capacitance-voltage in dark, barrier height measurements, power output characteristics.

Electrical and optical properties of Schottky diodes fabricated by electrodeposition of Ni films on n-GaAs

In this paper, we report electrical and optical characteristics of the Schottky diodes fabricated by electrodeposition of nickel onto n -GaAs substrate from 0.125 M NiSO 4 + 0.25 M H 3 BO 3 + 0.25 M Na 2 SO 4 solution. The electrodeposition was performed at room temperature and at − 1.5 V vs. SCE. Electrical and optical properties were measured in the temperature range of 200–360 K. Dark and light current-voltage ( I-V ) characteristics were investigated. Ideality factor, n and zero-bias barrier height, ϕ b were calculated and found to be almost constant in this temperature range. For room temperature, these values were obtained as 1.05 and 0.70 eV, respectively. Illuminated I-V characteristics were also investigated and they showed that the fabricated device could operate in photovoltaic regime. Open-circuit voltage, V oc was found to be 0.24 V for the diode under 20 mW/cm 2 illumination. • Good light sensitivity is achieved by electrodeposition. • Room temperature n and ϕ b values are 1.05 and 0.70 eV, respectively. • Electrodeposited Ni/ n -GaAs Schottky diode can operate in photovoltaic regime.

INVESTIGATION OF THE CURRENT-VOLTAGE CHARACTERISTICS OF THE N-CDS/P-CU(IN, GA)SE2 HETEROSTRUCTURE

In this work, current transfer mechanism in the n-CdS/p-Cu(In, Ga)Se2 heterostructure in the forward and reverse current directions at T=300 K is investigated. It has been established that the dark current-voltage characteristics of heterostructures built on a double logarithmic scale are described by power-law dependences type of the I=Vα. In the forward direction of the current, sections of the current-voltage characteristic were observed: α1=1 (ohmic) and α2=2 (quadratic), and for the reverse section of the current-voltage characteristic: α1=1 (ohmic), α2=0.25. From the quadratic section of the forward branch, the value µn∙τn=4.5∙10-10 cm2/V for the CIGS active layer was determined, which is explained by the processes of recombination of charge carriers through simple local centers.

ITO‐Free Indoor OPV Modules from Nonhalogenated Solvents

The growing market of the internet‐of‐things (IoT) accelerates the development of indoor organic photovoltaics. Very high performances up to 29% are already achieved under illumination with white light‐emitting diodes with intensities in the range of 500–1000 lux. However, topics relevant for mass production such as large area coating, use of nontoxic solvents, and inexpensive electrodes are hardly addressed thus far. Herein this work, an indium‐tin‐oxide‐free device stack is presented, which shows very good performance with many novel absorber materials under both full sun light as well as indoor illumination. Furthermore, lab‐scale cells are upscaled to small modules that can power typical IoT devices. This includes the transition from spin coating to slot‐die coating as well as the use of green solvents. Further, as the parallel resistance (RP) is crucial for the performance under low illumination intensities, a detailed analysis is carried out and it is found that a one‐diode model with the RP being determined from the dark current–voltage characteristics reproduces the behavior quite accurately. Efficiencies of 19.3% on cell level and above 17% on an 8.1 cm2 module with eight interconnected cells are achieved under 500 lux cold white light‐emitting diode illumination.

Current-Voltage Characterization of Multi-Port Graphene Based Geometric Diodes for High-Frequency Electromagnetic Harvesting

In this contribution, geometric diodes based on graphene patterned with spatial asymmetry have been studied, starting from tight-binding numerical approximation in a self-consistent framework, to verify their potential for electromagnetic (e. m.) harvesting. We report a detailed analysis of coherent charge transport and provide some figures of merit with respect to e. m. rectification, such as, for instance, the asymmetry of the dark current-voltage characteristics. The most important achievement of this work is given by the accurate analysis of the main key physical/geometric parameters that affect the nonlinear response of the diodes, for different configurations and geometries. Owing to the Scattering Matrix approach, introduced elsewhere for coherent transport calculation, it was possible to cascade asymmetric discontinuities and simulate large structures (more than 100K atoms) in a modular fashion. In this way, simulation at the atomistic level can be brought up to the device level to provide guidelines for design and fabrication, in view of practical applications related to clean-energy harvesting/rectification up to infrared and solar-light frequencies.

Electrical and Optical Characterization of Non-Hydrogenated a-Si/c-Si Heterojunction Solar Cells

This work deals with the performance of a heterojunction with intrinsic thin layer solar cell by sputtering silicon on p-type crystalline silicon substrate in argon ambient without hydrogen addition. This first effort was an attempt to use cost-effective means to convert light into electricity and to find fabrication processes which use fewer and cheaper materials for the fabrication of solar cells. Since transport mechanisms of amorphous silicon/crystalline silicon heterojunctions are still under investigation, the aim is to examine the behavior of the fabricated samples under electrical and optical constraints. Initial cell characterization includes electrical behavior via current-voltage characteristics and optical investigation via reflectance and absorptance measurements. Results are analyzed in a tentative to follow the absorption, generation and collection processes in the fabricated cell. The heterojunction interface is found to be a limiting factor in the cell performance. Under sun illumination, the open circuit voltage was 140 mV, the short circuit current was of 6 µA and the fill factor was of 42.56 %. Dark current-voltage characteristics indicated a tunneling and/or recombination carrier transport mechanism, while aborptance/reflectance measurements showed a generation process occurring in most in the crystalline silicon-side of the amorphous/crystalline silicon heterojunction. A carrier collection limitation is a very probable origin of the decreased cell generated current.

Radiation tolerance of GaAs1-xSbx solar cells

High radiation tolerance of GaAs1-xSbx based solar cells is demonstrated for the low-intensity-low-temperature (LILT) conditions of the target planets Saturn, Jupiter, and Mars. The GaAs1-xSbx-based cells are irradiated with high energy electrons to assess the effect of harsh radiation environment on the solar cell and the response of the cell is then investigated in terms of its photovoltaic operation. This system shows significant radiation resistance to the high energy electron environment for the conditions of the planets of interest. An unusual increase of the short circuit current after irradiation is observed at low temperature, which is supported by a simultaneous increase in the external quantum efficiency of the cell under the same conditions. The open circuit voltage and fill factor of the cell are especially tolerant to irradiation, which is also reflected in unchanged dark current-voltage characteristics of the solar cell upon irradiation particularly at LILT.

Effective role of temperature in improving the structural, optical and photovoltaic characteristics for n-Zn0.5Cd0.5Te/p-CdTe solar cells

The fabrication of Zn0.5Cd0.5Te thin film was reported in this study which was prepared via the common vacuum evaporation process at various temperatures (25, 100, 200, 300, 400 and 500 °C). On pre-cleaned glass substrates, the Zn0.5Cd0.5Te thin films were formed. The absorption coefficient was used to analyze the linear optical path in this study. The optical parameters, the optical constants, the dielectric constants, the quality factor of the studied thin films and the dispersion parameters were computed. The envelope approach, proposed by Swanepoel, was used to calculate the refractive indices and the thickness of the studied films in the transparent region. The optical energy gap was computed in the transmittance and reflectance spectrum's strong absorption zone. As the temperature of the examined system is increased, the refractive index, n, decreases while the energy gap rises. The annealed thin films have a crystalline structure with cubic phase and primarily oriented along the (111) plane, according to x-ray diffraction results. The crystalline structure of the examined thin films was confirmed by the top view of SEM profiles for the Zn0.5Cd0.5Te thin film at various temperatures. In the other part of this work, the photovoltaic characteristics of the fabricated n-Zn0.5Cd0.5Te/p-CdTe solar cell were investigated for a solar cell which fabricated by depositing a p-CdTe thin layer (200 nm) on the ZnCdTe thin films (∼1000 nm) prepared on the glass substrates (2 mm). The Ni/n-Zn0.5Cd0.5Te/p-CdTe/Pt heterojunction has been effectively assembled. The front and back contact electrodes were made of two high-work-function metals (Pt and Ni) so that surface electrons may travel freely and be easily removed from the surface by the influence of the lowest energy falling on the solar cell. The dark (current-voltage) characteristics of fabricated heterojunctions have been reported at different temperatures ranging from 25 to 500 °C, as well as for voltages ranging from −2 to 2 V. Based on the dependence of the forward and reverse current on the voltage, the effective and main parameters connected to the fabricated diode have been determined. The rectification ratio, the junction resistance, an ideality factor of the fabricated diode, the shunt and series resistances, the height of the barrier formed at the interface between the Zn–Cd–Te thin films and the p-CdTe thin layer, the carrier recombination, the activation energy in the exhausted region, Poole-Frenkel, and Schottky coefficients were all evaluated.

Erratum: “Dark current–voltage characteristics of vacuum deposited multilayer amorphous selenium-alloy detectors and the effect of x-ray irradiation” [J. Vac. Sci. Technol. A 37, 061501 (2019)

Erratum: “Dark current–voltage characteristics of vacuum deposited multilayer amorphous selenium-alloy detectors and the effect of x-ray irradiation” [J. Vac. Sci. Technol. A 37, 061501 (2019)

Study on the series resistance of crystal violet dye-based organic photovoltaic device in presence of single walled carbon nanotubes

The series resistance (Rs) of any organic photovoltaic device (OPV) plays an important role on the device performance. Generally, the electrode and the presence of traps at the interface contribute the high Rs. In this present work, we have studied the Rs of crystal violet dye-based OPV device and its variation in the presence of single walled carbon nanotubes (SWCNT). From the dark current voltage (I–V) characteristics, we have extracted Rs by using the Cheung–Cheung method. It is observed that the trap energy (Ec) and the value of Rs are decreased in the presence of SWCNT. The values of Rs and Ec are about 0.246 MΩ and 0.085 eV in the absence of SWCNT and these values change to 0.124 MΩ and 0.060 eV, respectively, in the presence of SWCNT. The light I–V characteristics of the devices have also been studied to find out the Rs of the device under illumination. Under illumination, the charge transport process is governed by the incident photon energy (Em) which is absorbed by the OPV device. So we have extracted the Em from the light I–V characteristics and estimated the Rs by using area method under light illumination in the absence and presence of SWCNT. It is observed that the extracted values of Rs under illumination are low compared to the values of Rs measured from dark I-V characteristics.