Voltage Characteristics In Dark Research Articles

Photovoltaic Solar Application Study of Cu0.5Zn0.5Se Thin Films by Chemical Bath Deposition Method

Inorganic ternary type materials are induced compound is worked as fundamental applications in transformation of the solar light energy into electrical energy. Copper zinc selenide thin films have been synthesized by chemical bath deposition method on to stainless steel plate. The configuration of fabricated cell is p-Cu0.5Zn0.5Se| NaOH(1M) + S(1M) + Na2S(1M) |C(graphite). The Photovoltaic cell characterization of the films is carried out by studying current–voltage characteristics in dark, capacitance–voltage in dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that Cu0.5Zn0.5Se thin films are p-type conductivity. The junction ideality factor was found to be 2.93. The flat band potential was found to be -0.708V. The barrier height value was found to be 0.186 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency were found to be 150 mV, 21 μA, 42.13%, and 0.63%, respectively. Photoresponse shows lighted ideality factor is 2.89. Spectral response shows the maximum current observed at 580 nm.

PPV derivative/ZnO nanorods heterojunction: Fabrication, Characterization and Near-UV light sensor development

Poly(1,4-phenylenevinylene) derivative (PPV-C6) based solution was spin-coated onto hydrothermally grown and vertically aligned ZnO nanorods (ZnO NRs).The morphological and the optical properties of the PPV-C6/ZnO NRs hybrid heterojunction have been studied and shown a penetration of PPV-C6into the interspaces between the ZnO NRs with enhanced excitonic dissociation. The current–voltage characteristics in dark and under 395 nm LED illumination have been analyzed. A short-circuit current Jsc of 4691.42 μA/cm2, an open-circuit voltage Voc of 0.46 V giving rise to a responsivity of about 29.32 mA/W have been obtained for the illuminated graphite/PPV-C6/ZnO NRs/Si/EGa-In structure based near UV light sensor showing an enhanced responsivity by a factor of about 200 compared with bare ZnO NRs based one. We have succeeded in the development of low cost near-UV light sensors by simple low temperature hydrothermal method using eco-friendly, low cost and easily fabricated electrodes.

BaBiO3: A potential absorber for all-oxide photovoltaics

BaBiO3 is presented as a potential absorber for all-oxide solar cells. Thin-films of BaBiO3 were deposited by pulsed laser deposition. As-deposited thin-films were amorphous, but a rapid thermal anneal at 600°C for 10min yields polycrystalline thin-films. X-ray photoelectron spectroscopy measurements show that deposited films have Barium in Ba+2 state and bismuth in both Bi+3 and Bi+5 state. UV–Vis spectrophotometer (UV–Vis) shows that BaBiO3 films have direct and indirect bandgap (Eg) of 2.25eV and 2.02eV respectively, while ultraviolet photoelectron spectroscopy (UPS) shows that valence band maxima (EV), conduction band minima (EC) and work-function (ϕ) of BaBiO3 is at 5.82eV, 3.8eV and 4.22eV respectively. BaBiO3 thin-film devices with a FTO/c-TiO2/BaBiO3/Au structure show rectifying current–voltage characteristics in dark. Under illumination, a photo response with a Jlight/Jdark ratio of 1.75 is observed.

GLANCING ANGLE REACTIVE PULSED LASER DEPOSITION (GRPLD) FOR Bi2O3/Si HETEROSTRUCTURE

Thin films of micro bismuth oxide particles were successfully prepared by in situ oxidation of the laser ablated bismuth metal. (111) oriented p-type crystalline silicon substrates were used. The effects of substrate tiled angle on the characteristics of the prepared film were studied. Also, the performance of n- Bi 2 O 3/p- Si heterojunction device was investigated. The obtained current–voltage characteristics in dark and under illumination insure the dependence of the fabricated device characteristic on the deposition angle. The I–V characteristics show that all prepared devices are of abrupt type.

Effect of Fe-incorporation on photovoltaic characteristics of nano-structured CdSe thin films

The Fe-incorporated CdSe films are deposited on FTO-coated glass substrates by computerized spray pyrolysis technique. The Fe concentration is optimized by using photoelectrochemical (PEC) technique. The cell configurations CdSe/1M (Na2S+S+NaOH)/C and Fe:CdSe/1M (Na2S+S+NaOH)/C are used to study a wide range of photoelectrochemical characteristics including capacitance–voltage characteristics in dark, current–voltage characteristics in the dark and under illumination, photovoltaic power output and spectral response and to perform electrochemical impedance spectroscopy studies. The study reveals that the films exhibit n-type conductivity. Various parameters such as the junction ideality factor under illumination, series and shunt resistances, fill factor and efficiency are estimated for the PEC cell formed with CdSe and Fe-incorporated CdSe thin films. Band edges of Fe incorporated CdSe thin films are located. The best result obtained for conversion efficiency is 1.48% at 0.30mol% Fe, which is three times more than the one reported for pure CdSe (0.50%) material. The value of fill factor is found to be improved from 0.44 to 0.63 with Fe incorporating in CdSe thin films. Electrochemical impedance spectroscopy studies show that incorporating of Fe into CdSe thin film improves the performance of resulting PEC cells. The utility of this work is in improving in efficiency of the PEC solar cell.

Large-area and nanoscale n-ZnO/p-Si heterojunction photodetectors

The article reports the results of our experimental investigation on the effect of UV light on the characteristics of n-ZnO/p-Si heterojunction. c-Axis oriented zinc oxide (ZnO) films were deposited by thermal evaporation technique on p-type silicon (Si) substrates to form ZnO/Si heterojunctions. Both large-area and nanoscale heterojunction configurations were studied. The measured current–voltage characteristics in dark and illuminated conditions confirm the rectifying behavior of the heterojunctions and an excellent UV response. The responsivity values were measured to be of 0.18 and 0.12 A/W to UV light (365nm) for large-area and nanoscale heterojunctions, respectively. The values are comparable with those offered by other commercial UV detectors. The nanoscale heterojunction device can find applications in nanophotonics.

Chemical deposition of CuInSe 2 thin films by photoelectrochemical applications

Copper indium diselenide films have been synthesized by chemical bath deposition method. The configuration of fabricated cell is n-CuInSe 2|NaOH (1 M) + S (1 M) + Na 2S (1 M)|C (graphite). The photoelectrochemical cell characterization of the films is carried out by studying current–voltage characteristics in dark, capacitance–voltage in dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that CuInSe 2 thin films are n-type conductivity. The junction ideality factor is found to be 3.81. The flat band potential is found to be 0.763 V. The barrier height value is found to be 0.232 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency are found to be 310 mV, 20 μA, 42.12% and 0.82%, respectively. Photoresponse shows lighted ideality factor which is 2.92. Spectral response shows the maximum current observed at 650 nm.

Effect of surface modification of TiO 2 on the photovoltaic performance of the quasi solid state dye sensitized solar cells using a benzothiadiazole-based dye

We report the preparation of nanoporous TiO 2 electrode modified with an insulating material—BaCO 3 and used as electrode for quasi solid state dye sensitized solar cells (DSSCs), with a benzothiadiazole-based dye (BTDR2) as sensitizer and PEDOT:PSS coated FTO as counter electrode. We found that the BaCO 3 modification significantly increases the dye adsorption, resulting from the fact that the surface of BaCO 3 is more basic than TiO 2. The performance of the DSSCs with and without BaCO 3 modified TiO 2 electrodes were analyzed by cyclic voltammograms, optical absorption spectra, current–voltage characteristics in dark and under illumination and electrochemical impedance spectra. The photovoltaic performance has been significantly improved for the BaCO 3 modified electrode as compared to bare TiO 2 electrode having the same other components in the DSSCs. The value of the overall power conversion efficiency ( η) improves from 2.42% to 4.38% under illumination intensity, when BaCO 3 modified electrode is used instead of bare TiO 2 electrode. The improvement in η has been attributed to the increased dye adsorption, reduction in recombination rate and enhancement in the electron lifetime when the modified TiO 2 electrode is used.

Zinc sulphide semiconductor electrode synthesis and the photoelectrochemical application

Zinc sulphide photoelectrodes have been synthesized by dip method onto stainless steel plate. The configuration of fabricated cell is n-ZnS|NaOH (1 M) + S (1 M) + Na 2S (1 M) |C (graphite) .The photoelectrochemical characterization of the photoelectrode is carried out by studying current–voltage characteristics in dark, capacitance–voltage in dark, power output and photoresponse. The study shows that ZnS photoelectrodes are n-type conductivity. The flat band potential is found to be −0.546 V (saturated calomel electrode). The junction ideality factor was found to be 3.12. The study of power output characteristics shows open circuit voltage, short circuit current, fill factor and efficiency was found to be 206 mV, 68 μA, 37.47% and 0.53% respectively. Photoresponse shows that lighted ideality factor is 3.78.

Low band gap vinylene compounds with triphenylamine and benzothiadiazole segments for use in photovoltaic cells

Two new soluble vinylene compounds, TPA-TNP and BTD-TNP, which contained triphenylamine and benzothiadiazole segments, respectively, and terminal p-nitrophenyl units were synthesized and characterized. They showed high thermal stability with decomposition temperature above 450 °C. Their absorption was broad and extended up to about 800 nm with optical band gaps of 1.65–1.67 eV. The long wavelength absorption maximum was located around in between 638 and 650 nm. The presence of the electron-withdrawing nitro groups on the terminal phenyls broadened the absorption of these compounds. The current–voltage characteristics in dark and the IPCE spectra of the devices based on these compounds revealed that these materials behave as p-type organic semiconductors with hole mobility of the order of 10 −5 cm 2/V s. The photovoltaic properties of these compounds blended with PCBM were investigated and the power conversion efficiency is 1.13% and 1.32% for TPA-TNP and BTD-TNP, respectively. The device with thermally annealed BTD-TNP photoactive film shows power conversion efficiency of about 2.42%.

Synthesis, photophysics of two new perylene bisimides and their photovoltaic performances in quasi solid state dye sensitized solar cells

Two new symmetrical compounds A and P based on perylene-anthracene and perylene-pyrene, respectively, were synthesized and characterized by FT-IR, 1H NMR, TGA and TMA. These compounds contained tert-butyl groups which enhanced their solubility, decomposed above 400 °C and gave char yields of 46–65% at 800 °C in N2. Compound A showed significantly higher glass transition temperature (124 °C) than P (75 °C). Their absorption spectra were broad with longer wavelength absorption at 467–525 nm and optical band gap of 2.05 eV. The solutions of the compounds emitted green-yellow light with maximum at 555 nm, while their films were not photoluminescent. The compound A shows better photovoltaic response than compound P. Quasi solid state dye sensitized solar cells (DSSCs) have been fabricated employing compound A as sensitizer and polymer sol gel as electrolyte and characterized through the current–voltage characteristics in dark as well as under illumination and electrochemical impedance spectra. We found that the Al2O3 modification of TiO2 layer significantly improves the dye absorption resulting in enhancement of power conversion efficiency (PCE) (from 1.15 to 2.13%) which is attributed to the increase in electron lifetime and reduction in back transfer of electrons. Finally, the TiO2 has been incorporated into the polymer electrolyte gel to improve the power conversion efficiency (3.42%) of the quasi solid state DSSC. The faster electron diffusion in the device, the high ionic conductivity and the low activation energy of the polymer electrolyte are also responsible for enhanced PCE, when TiO2 nano-particles are incorporated in the polymer electrolyte.

Photoelectrochemical studies of CdSe thin films deposited by dip method

Cadmium selenide photoelectrodes have been synthesized by chemical bath method onto stainless steel plate. The configuration of fabricated cell is n-CdSe|NaOH (1 M) + S (1 M) + Na 2S (1 M)|C (graphite). The photoelectrochemical cell characterization of the photoelectrodes is carried out by studying current–voltage characteristics in dark, capacitance–voltage in dark, barrier-height measurements, power output, photoresponse and spectral response. The junction ideality factor was found to be 3.23. The flat band potential was found to be 0.7 V. The barrier-height value was found to be 0.186 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency was found to be 260 mV, 169 μA, 36.91% and 0.55%, respectively. Photoresponse shows lighted ideality factor is 4.06. Spectral response shows the maximum current observed at 730 nm.

Chemical deposition of ZnSe thin films: Photoelectrochemical applications

Abstract Zinc selenide films have been synthesized by chemical bath deposition method onto stainless steel plate. The configuration of fabricated cell is n-ZnSe|NaOH (1 M) + S (1 M) + Na2S (1 M)|C(graphite) .The photoelectrochemical cell characterization of the films is carried out by studying current–voltage characteristics in dark, capacitance–voltage in dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that ZnSe thin films are n-type conductivity. The junction ideality factor was found to be 3.85. The flat band potential is found to be −0.530 V. The barrier height value was found to be 0.171 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency was found to be 153 mV, 20 μA, 29.41% and 0.13%, respectively. Photoresponse shows lighted ideality factor is 6.78. Spectral response shows the maximum current observed at 440 nm.

Charge generation and photovoltaic properties of hybrid solar cells based on ZnO and copper phthalocyanines (CuPc)

Photovoltaic properties and charge transfer process within the blend of p-type organic semi conducting copper phthalocyanine (CuPc) and inorganic n-type semiconductor zinc oxide (ZnO) nanoparticle have been determined. The photo-induced electron transfer mechanism in the composite thin film structure is predicted on the basis of its optical absorption behavior, photo-action spectra and photoluminescence (PL) characteristics, supported by current–voltage characteristics in dark and under illumination. An efficient electron transfer between donor (CuPc) and acceptor (ZnO) nanoparticle is explained by analyzing the photo-action spectra of the device and respective quenching of photoluminescence (PL) in composite thin film structure. The increase in photocurrent in composite blend based device is justified in terms of formation of bulk heterojunction between CuPc and ZnO nanoparticles. Also, the subsequent increase in photovoltaic response is ascribed to the formation of interconnecting network in between CuPc and ZnO nanoparticles. Our experimental results supports that photo-generation of charge carriers is induced by the production of excitons and their subsequent dissociation of into free carriers at ZnO–CuPc interface which is spread over the bulk region sandwiched between Al and ITO. Additionally, the optical and electrical properties of the composite blend based device have been discussed in details. The capacitance–voltage characteristics of the device support the formation of bulk heterojunction between CuPc and ZnO nanoparticles.

Charge-carrier transport and photogeneration processes in pyronine (G) (PYR) sensitized-TiO2 photovoltaic device

Steady-state current–voltage characteristics in dark and under illumination, along with impedance characteristics at different biasing voltages, were investigated on solid film of pyronine (PYR) sensitized-TiO2, sandwiched between ITO and Al electrodes. The J–V characteristics of the material in dark were explained by the formation of percolation network of nano particles between the electrodes. The device ITO/TiO2–PYR/Al device shows rectification below 2.5 V and becomes symmetrical at higher voltages. Dark current increases by two orders, which indicates that charge-carrier transport occurs not only in the organic phase, but also involves processes in nano particles. The impedance characteristics (variation of imaginary impedance with real impedance) at different biasing voltages show two semicircles at voltage below 2.5 V, and beyond which only one semicircle was observed. This also indicates that at low voltages the device exhibits rectification, and above 2.5 V, both the interfaces behave as Ohmic contact. This observation is also confirmed from impedance spectroscopy. The photoaction spectra of the device-based-composite containing PYR-sensitized-TiO2 is different from the photoaction spectra of the device employing pure PRY. The charge collection efficiencies for the PYR–TiO2 composite increases under both forward bias and reverse bias. This indicates that the same process governs photocurrent multiplication for both bias directions.

Charge-carrier transport and photogeneration processes in pyronine (G) (PYR) sensitized-TiO 2 photovoltaic device

Steady-state current–voltage characteristics in dark and under illumination, along with impedance characteristics at different biasing voltages, were investigated on solid film of pyronine (PYR) sensitized-TiO 2, sandwiched between ITO and Al electrodes. The J– V characteristics of the material in dark were explained by the formation of percolation network of nano particles between the electrodes. The device ITO/TiO 2–PYR/Al device shows rectification below 2.5 V and becomes symmetrical at higher voltages. Dark current increases by two orders, which indicates that charge-carrier transport occurs not only in the organic phase, but also involves processes in nano particles. The impedance characteristics (variation of imaginary impedance with real impedance) at different biasing voltages show two semicircles at voltage below 2.5 V, and beyond which only one semicircle was observed. This also indicates that at low voltages the device exhibits rectification, and above 2.5 V, both the interfaces behave as Ohmic contact. This observation is also confirmed from impedance spectroscopy. The photoaction spectra of the device-based-composite containing PYR-sensitized-TiO 2 is different from the photoaction spectra of the device employing pure PRY. The charge collection efficiencies for the PYR–TiO 2 composite increases under both forward bias and reverse bias. This indicates that the same process governs photocurrent multiplication for both bias directions.

Investigation of non-aqueous electrodeposited CdS/Cd1−xZnxTe heterojunction solar cells

Polycrystalline Cd1−xZnxTe solar cells with efficiency of 8.3% were grown by cathodic electrodeposition on glass/ITO/CdS substrates using non-aqueous ethylene glycol bath. The deposit is characterised versus the process conditions by XRD and found to possess a preferred (1 1 1) orientation on Sb doping in the electroplating bath. The surface morphology of the deposit is studied using atomic force microscope. The average RMS roughness for the ternary film was higher than that for the binary CdTe. Optical properties of the films were carried out to study the band gap and calculation of molar concentration ‘x’. The effects of Sb doping in CdS/Cd1−xZnxTe heterojunctions have been studied. The short circuit current density (c) was found to improve and series resistance (Rs) reduced drastically upon Sb doping. This improvement in Jsc is attributed to an increase in quantum efficiency. The evaluation of solar cell parameters was also carried out using the current–voltage characteristics in dark and illumination. The best results were obtained when 2×10−3 M ZnCl2 along with antimony were present in the deposition bath. Under AM 1.5 conditions the open circuit voltage, short circuit current density, and fill factor of our best cell were Voc=600 mV, Jsc=26.66 mA/cm2, FF=0.42 and efficiency, η=8.3%. The carrier concentration and built-in potential of Cd1−xZnxTe calculated from Mott–Schottky plot was 2.72×1017 cm−3 and 1.02 eV.

Uncooled micro-bolometer based on amorphous germanium film

The fabrication and characterization of an uncooled micro-bolometer, in which the sensing material is amorphous germanium (a-Ge:F) is presented. In order to obtain thermal isolation, the micro-bolometer was fabricated on a silicon dioxide membrane, which was made on a silicon wafer by micro-machining techniques. The sensing layer was deposited from GeF 4 + H 2 mixture by low frequency plasma-enhanced chemical vapor deposition. The a-Ge:F film had high thermal coefficient of resistance at room temperature α=0.04 and moderate conductivity σ RT=2.5×10 −3 Ω −1 cm −1. The micro-bolometer was characterized by the measurements of current–voltage characteristics in dark and under infrared illumination with a black body at temperature T bb=1123 K. Thermal and noise characteristics were also measured. The micro-bolometer having the pixel area A d=60×60 μm 2 demonstrated thermal resistance R th=5×10 6 K W −1, current responsivity R I =6.2 mA W −1, voltage responsivity R V =4.2×10 6 V W −1 and detectivity D ∗=8×10 6 cm W Hz 1/2.

Photoelectrochemical characterization of Bi 2Se 3 thin films deposited by SILAR technique

Bi 2Se 3 thin films have been deposited by simple and less investigated successive ionic layer adsorption and reaction (SILAR) technique onto fluorine-doped tin oxide (FTO) coated glass substrates at room temperature (27 °C). The X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies indicate that Bi 2Se 3 thin films are nanocrystalline. These films are used for photoelectrochemical (PEC) characterization in cell with configuration as n-Bi 2Se 3/0.1 M polysulfide/C. The studies such as current–voltage characteristics in dark and light, photovoltaic power output, transient photoresponse, and capacitance–voltage have been carried out. The study reveals that fill factor and power conversion efficiency of the cell are low (0.43 and 0.032%, respectively).The flat bond potential is found to be −0.04 V (SCE).

Studies on K-Sb-S films deposited at different substrate temperatures and their photoelectrochemical behaviour

The electrical and optical properties of thin films of K-Sb-S prepared by spraying a solution of antimony potassium tartrate and thiourea onto heated conducting and non-conducting glass substrates are described. The polycrystalline films produced at an optimum spray rate and at different substrate temperatures were characterized for semiquantitative analysis. The films show variation in thickness with substrate temperature. Photoelectrochemical cells formed with the K-Sb-S film electrode, 0·5 M ferrocene in dimethylsulphoxide as the electrolyte and carbon as the counterelectrode were studied for their current voltage characteristics in dark and in light. Variation of short circuit current and open circuit voltage with light excitation intensity is also described.