Photovoltaic Activity Research Articles

Novel and green synthesis of chemically reduced graphene sheets using Phyllanthus emblica (Indian Gooseberry) and its photovoltaic activity

The study presents a novel and environment friendly procedure for obtaining chemically reduced graphene sheets (CRGs). Graphene Oxide as precursor material and Phyllanthus Emblica fruit extract as reductant. This procedure is suitable for mass production of graphene. Characterization of graphene flakes has subsequently been done using Raman spectroscopy, DLS, Fourier transform infrared spectroscopy (FTIR), x-ray-diffraction (XRD) and UV–vis spectroscopy. A reduction was observed in the oxygen containing functionalities of graphene oxide. Presence of Graphene layers was also confirmed by morphological studies like SEM and TEM. Further thermal strength of precursor material and its product was investigated by TGA. The strategy is successful in obtaining graphene which subsequently may be utilized in supercapacitors, sensors, and electronic devices. Its photovoltaic performance has also been compared with GO.

Ionothermal synthesis of a photoelectroactive titanophosphite with a three-dimensional open-framework

A new titanophosphite open-framework exhibits photovoltaic properties and photocatalytic activity as an n-type semiconductor.

One-step hydrothermal synthesis of Ag decorated TiO2 nanoparticles for dye-sensitized solar cell application

Over the past few years, many efforts have been made to develop efficient visible light-activated photovoltaic materials. In this study, the Ag-TiO2 nanoparticles were synthesized by using the hydrothermal method. Ag-TiO2 nanoparticles showed significantly higher visible light absorption and better photovoltaic activity than anatase TiO2. TiO2 nanoparticles were decorated with different concentrations of Ag to improve their photovoltaic properties. All the as-prepared TiO2 and Ag-TiO2 nanoparticles showed a pure anatase crystalline structure. In addition, the Ag-doped nanoparticles showed broader absorption edges (which shifted to higher wavelengths) than the undoped nanoparticles. The solar conversion efficiency (η) of 0.1M Ag-decorated (Ag0.1-TiO2) nanoparticle-based dye-sensitized solar cell (DSSC) was 6.44%, which is ∼22% higher than that of the TiO2 nanoparticle-based DSSC (η of 5.05%).

Fabrication (PANI-CSA) /n-Si) solar cell from nano conducting polymers PANI doped with CSA

Polyaniline (PANI) doped with CSA was synthesis by chemical polymerization method using ammonium persulphate as oxidizing agent. Thin films of (PANI-CSA) have been prepared by spin coating method and characterized by (FTIR) spectra. Morphology and diameters of the nanoconducting polymer were measured by Atomic Force Microscope (AFM). Solar were fabricated by depositing thin films of polyaniline (PANI) doped with CSA acid onto n-type Si wafers using spin coating method. The J-V characteristics of this hybrid solar cell were studied in the dark and under illumination and photovoltaic activity is clearly demonstrated. The PANI-CSA /n-Si solar cells obtained in this work have yielded a conversion efficiency η = 4% with short circuit current (Jsc) of 1.86 mA/cm2 and open circuit voltage (Voc) of 202 mV under AM 1.5 solar simulator (100 mW/cm2).

Cu2SnS3 based thin film solar cells from chemical spray pyrolysis

A simple and eco-friendly method for solution processing of Cu2SnS3 p-type semiconductor absorbers using a water-based precursor solution is presented. Cu2SnS3 layers were processed by chemical spray pyrolysis deposition of the precursor solution onto Mo-coated glass substrates at 350 °C. The as-prepared layers were placed inside a graphite susceptor with S and SnS powders and were annealed in a tube furnace at 550 °C. The impact of the annealing step on structural, morphological and device characteristics of the prepared layers was studied.The as-prepared layers were crack-free with fine grains and dominant tetragonal Cu2SnS3 structure. A denser and compact Cu2SnS3 layer with larger grains was formed upon annealing accompanied by a structural phase transition from the tetragonal polymorph to the monoclinic phase. The as-prepared Cu2SnS3 layers showed no photovoltaic activity, whereas the annealed layers showed a device efficiency of 0.65%. A short air annealing of the complete Cu2SnS3 device at 250 °C improved the overall device performance and increased the device efficiency to 1.94%. Mechanical removal of shunt paths led to Cu2SnS3 device with 2.28% efficiency.

Cu2O@CuO core-shell nanoparticles as photocathode for p-type dye sensitized solar cell

Cu2O@CuO core-shell nanoparticles were synthesized via a facile precipitation-thermal oxidation method consisting in the preparation of Cu2O nanoparticles in solution followed by a post-treatment at 300 °C, 350 °C or 400 °C in air. From HRTEM micrographs, it was evidenced that Cu2O particles were uniformly covered by a 5 nm thick CuO layer to form a core-shell structure. This shell may be viewed as a passivating layer that overcomes the natural chemical instability of Cu2O towards electrolytes for instance. The as-obtained Cu2O@CuO nanoparticles were characterized by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. Both techniques concluded to the p-type conductivity of the Cu2O@CuO hetero-structures. These nanoparticles were then deposited as a film on a FTO glass by screen printing and used after sintering as photocathodes for p-DSSCs. Photovoltaic activity was confirmed with DPP-NDI dye as sensitizer and tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) as redox mediator.

Synthesis of ZnO/NiO Thin Film on Fluorine-doped Tin Oxide (FTO) by Two Step Electrodeposition as Photoanode of a Solar Cell

Synthesis of ZnO/NiO Thin Film on Fluorine-doped Tin Oxide (FTO) by Two Step Electrodeposition has been conducted. The film was used as a photoanode of a solar cell. Synthesis was performed by two step electrodeposition with FTO as anode and carbon rod as cathode. NiO was firstly electrodeposited at 2.4 V from 0.2 M of NiCl2 solution at pH 11, 70°C, under stirring of 250 rpm after air bubbling. Second step, ZnO was electrodeposited at 2.6 V from precursor Zn(NO3) 0.2 M, pH 12, 70°C with air bubbling and stirring of 250 rpm. Product was then calcined at 450°C for 2 hours followed with XRD characterization. A solar cell was constructed by utilizing the ZnO/NiO film as photoanode related to aluminium plat as cathode. Data resulted showed that the efficiency in NiO deposition was 39.4% with mass of 8 mg and 16 µm in thin film size. Efficiency in ZnO deposition was 12.7% with mass of 14.7 mg and 11 µm in thin film size. XRD data informed that NiO and ZnO were thin filmed to FTO substrate with powder size of 30.31 nm and ZnO of 21.07 nm. Photovoltaic activity test with illuminating UV light 15 W onto the film resulted in that the average voltages of 240.93 mV and current density of 7.34 mA/cm2. Under tungsten light of 15 W illumination the system produced average voltages of 166.20 mV and current density of 5.48 mA/cm2. Finally, the solar cell was tested under 7 W-LED illumination that was calibrated to silicon solar cell equal to sun light of 1.5 AM (100 mW/cm2) resulted in efficiency of 0.027%.

Thin film photovoltaic devices prepared with Cu3BiS3 ternary compound

Current commercial thin film photovoltaic technologies rely on the use of scarce and/or toxic elements, motivating the necessity to explore new technologies free of critical raw materials. In this work we report the first Cu3BiS3 based solar cells with proved photovoltaic activity using standard substrate configuration. The absorbers were synthesized using a sequential process based on metallic stacks evaporation followed by a reactive annealing under S atmosphere. With the optimization of composition (Cu/3: Bi ratio), metallic stack order, annealing parameters and Na doping, we achieve a record conversion efficiency of 0.11%. Combining several characterizations techniques, we show that at this stage of the technology development, issues like composition, secondary phases and morphology cannot explain the low efficiencies obtained with this material. Through a deeper characterization of the devices, we found that most probably, this is related to either, a high doping of the absorber, and/or poor transport charge properties. Understanding and solving these issues, can further help to improve the efficiency of Cu3BiS3 based devices towards more competitive conversion efficiencies.

Computational modeling of the photovoltaic activities in EABX3 (EA = ethylammonium, B = Pb, Sn, Ge, X = Cl, Br, I) perovskite solar cells

In this work, the effects of the metal cations and halide anions on the performance of ethylammonium-based perovskite solar cells (PSCs) were investigated. For this purpose, hole transfer material (HTM) and EABX3 (EA = ethylammonium, B = Pb, Sn, Ge, X = Cl, Br, I) perovskite structures were considered from the theoretical viewpoint. Time-dependent density functional theory (TD-DFT) and natural bond orbital (NBO) analysis were applied. The molecular orbitals energy alignment of the materials involved in these PSCs as well as the negative values of Gibbs energies of the electron injection (ΔGinj.) at the EABX3/TiO2 interface and hole transfer (ΔGreg.) at the EABX3/HTM interface show that the studied structures can guarantee the basic photovoltaic processes in this type of solar cells. Based on the results, the coupling constant of EABX3/TiO2 (|VRP|) is the most important parameter that affects the photovoltaic properties of the PSCs and an increase in the size of the halides elevates the electron driving force (eVOC) and decreases |VRP|. A different behavior for the electron transfer rate constant (kinj.) against to the dynamic parameters of eVOC and exciton binding energy (EBE) of the photosensitizers was found. Moreover, the perovskites having a higher electric dipole moment (rk,ḱ) are able to harvest the incident photon and show a stronger dependence of the light harvesting efficiency (LHE) to rk,ḱ. Finally, on the basis of the analyses of LHE and the incident photon to current conversion efficiency (IPCE), EAGeCl3 was proposed as a more efficient compound to be used in the PSCs.

Control of the Polarization of Ferroelectric Capacitors by the Concurrent Action of Light and Adsorbates.

Ferroelectric perovskites hold promise of enhanced photovoltaic efficiency and photocatalytic activity. Consequently, the photoresponse of oxide ferroelectric thin films is an active field of research. In electrode/ferroelectric/electrode devices, internal charge in the ferroelectric, free charge in the electrodes, and buried adsorbates at interfaces combine to screen the ferroelectric polarization and to stabilize the polar state. Under illumination, photoinduced carriers and photodissociated adsorbates may disrupt the screening equilibrium, modifying the switchable polarization and altering its expected benefits. Here, we explore the photoresponse of BaTiO3 thin films in a capacitor geometry, focusing on the effects of visible illumination on the remanent polarization. By combining ferroelectric and X-ray photoelectron spectroscopy, we discover that photoreaction of charge-screening H2O-derived adsorbates at the buried metal-ferroelectric Pt/BaTiO3 interface plays an unexpected pivotal role, enabling a substantial modulation (up to 75%) of the switchable remanent polarization by light. These findings illustrate that the synergy between photochemistry and photovoltaic activity at the surface of a ferroelectric material can be exploited to tune photoferroelectric activity.

Origin of Different Photovoltaic Activities in Regioisomeric Small Organic Molecule Solar Cells: The Intrinsic Role of Charge Transfer Processes

Regioisomeric small organic molecules are recently reported to show remarkable difference in their photovoltaic activities when blended with suitable donor/acceptor counterpart. The structural difference as a result of positional diversity of the foreign substituent leads to different intermolecular interactions and dipolar orientations, and thus they acquire different morphologies. This severely influences the local transport and carrier recombination, leading to different photovoltaic power conversion efficiencies. However, the molecular level understanding relating to the carrier transfer and the associated dynamical properties remains unexplored, which could focus on the rational description of such phenomena. Herein, we apply the Marcus theory of electron transfer rates on some experimentally realized and model composite systems consisting regioisomeric molecules, which provides a general understanding of such intrinsic dynamical behavior, the precise control of which could offer better photovoltaic ...

How Transparent Oxides Gain Some Color: Discovery of a CeNiO3 Reduced Bandgap Phase As an Absorber for Photovoltaics.

In this work, we describe the formation of a reduced bandgap CeNiO3 phase, which, to our knowledge, has not been previously reported, and we show how it is utilized as an absorber layer in a photovoltaic cell. The CeNiO3 phase is prepared by a combinatorial materials science approach, where a library containing a continuous compositional spread of Ce xNi1- xO y is formed by pulsed laser deposition (PLD); a method that has not been used in the past to form Ce-Ni-O materials. The library displays a reduced bandgap throughout, calculated to be 1.48-1.77 eV, compared to the starting materials, CeO2 and NiO, which each have a bandgap of ∼3.3 eV. The materials library is further analyzed by X-ray diffraction to determine a new crystalline phase. By searching and comparing to the Materials Project database, the reduced bandgap CeNiO3 phase is realized. The CeNiO3 reduced bandgap phase is implemented as the absorber layer in a solar cell and photovoltages up to 550 mV are achieved. The solar cells are also measured by surface photovoltage spectroscopy, which shows that the source of the photovoltaic activity is the reduced bandgap CeNiO3 phase, making it a viable material for solar energy.

Dye sensitized solar cell based on environmental friendly eosin Y dye and Al doped titanium dioxide nano particles

Present communication deals with the development of cost effective dye sensitized solar cell (DSSC) with eco-friendly materials. Eco-friendly Eosin Y dye was used to sensitize photo anode which was fabricated using undoped and Aluminium doped titanium dioxide (TiO2) nanoparticles. Undoped and Aluminium doped TiO2 nanoparticles were synthesized by simple and cost effective sol-gel method. Aluminium doped and undoped TiO2 nanoparticles were characterized using UV-visible, FT-IR spectroscopy, x-ray Diffraction, and Scanning Electron Micrograph with EDX. The photo-voltaic activity of the cell was studied under light irradiation of 100 milliwatt cm−2. Aluminium doped TiO2 nanoparticle photo electrode exhibits more than 60% increase in cell efficiency as compared to the undoped TiO2 nanoparticle photo electrode.

Zener behaviour of p-SnS/ZnO and p-SnS/ZnS heterojunctions

p-SnS absorbing layers were grown by thermal evaporation on layers of various Zinc compounds, like ZnO and ZnS. This present work reports the J-V characteristics of thus obtained p-SnS/ZnO and p-SnS/ZnS heterojunctions. The pn junctions of these structures did not show any photovoltaic activity, however a zener like behaviour was observed in the 3rd quadrant of the J-V characteristics. Our analysis of the diodes suggest that the reverse breakdown or zener voltage obtained from the dark J-V characteristics can be used to estimate the energy band diagram of the junction and in turn the band-alignment at the junction. This makes it an easy alternative to x-ray Photoelectron Spectroscopy method usually used.

The influence of perovskite precursor composition on the morphology and photovoltaic performance of mixed halide MAPbI3-xClx solar cells

A set of various perovskite precursor formulations was investigated to elucidate correlations between precursor composition and the crystal structure, film morphology as well as photovoltaic activity of H3CNH3PbI3-xClx perovskite solar cells. Three precursor solutions in dimethylfromamide (DMF) with defined ratios of lead(II) halide (PbI2 and/or PbCl2) and methylammonium halide (H3CNH3I (MAI) and H3CNH3Cl (MACl)) such as 1:3 (PbCl2:MAI), 1:1:4 (PbI2:PbCl2:MAI) and 1:1:1 (PbI2:MAI:MACl) were used to prepare solar cells in primarily ambient atmosphere. Processing the 1:3 (PbCl2:MAI) solution in ambient atmosphere yielded perovskite films with rather non-uniform morphology and devices with moderate performance. Perovskite thin films prepared from the 1:1:4 (PbI2:PbCl2:MAI) and 1:1:1 (PbI2:MAI:MACl) formulation showed nearly identical features, high crystallinity, large and compact micrometer-sized crystal domains, and good photovoltaic performance. This indicates that the overall ionic composition in the precursor solution is crucial for the perovskite formation, the source of these ions, however, appears nonrelevant. Furthermore, the effect of different electron transport layers (ETL), PCBM, bis-PCBM, and N-[4-(benzothiadiazol-4-yl)phenyl]-N′-(1-nonyldecyl)perylene-3,4,9,10-tetracarboxdimide (a-PTCDI) on the photovoltaic performance was analyzed. The highest hysteresis-free power conversion efficiency (PCE) was achieved with PCBM (12.8%) followed by a-PTCDI (8.4%) and bis-PCBM (6%). The degradation of MAPbI3-xClx based devices stored in nitrogen atmosphere was primarily revealed by a loss in fill factor.

An investigation into the effect of rate of stirring of bath electrolyte on the properties of electrodeposited CdTe thin film semiconductors

Electrodeposition (ED) has been recognized as a low cost and scalable technique available for fabrication of CdS/CdTe solar cells. Photovoltaic activity of these electrodeposited semiconductor materials drastically depends on the ED growth parameters namely; electrodeposition potential, concentrations and ratios of concentrations of precursors used to prepare the bath electrolyte, pH of the electrolyte, deposition temperature and rate of stirring of the electrolyte. In order to grow thin films with good photovoltaic properties, it is essential to maintain these variables at their optimum ranges of values during electrodepositions. Hence, this study was conducted to investigate the dependence of the properties of electrodeposited CdTe thin film material on the rate of stirring of the bath electrolyte. The CdTe material was grown on glass/FTO (2 × 3 cm2) and glass/FTO/CdS (2 × 3 cm2) surfaces in bath electrolytes containing 1.0 mol/L CdSO4 and 1.0 mmol/L TeO2 solutions at different rates of stirring within the range of 0–350 rpm while keeping the values of pH of the electrolyte, deposition temperature and cathodic deposition potential with respect to the saturated calomel electrode at 2.3, 65 °C and 650 mV respectively. After the heat treatment at 400 °C in air atmosphere, the deposited samples with a good visual appearance were selected and evaluated based on their morphological, elemental, structural, optical and electrical properties in order to identify the optimum range of rate of stirring for electrodeposition of CdTe thin film semiconductors. Results revealed that, rates of stirring in the range of 60–85 rpm in a 100 mL volume of electrolyte containing the substrate and the counter electrodes in the center of the bath with a separation of 2.0 cm between them can electrodeposit CdTe layers exhibiting required levels of morphological, structural, optical and electrical properties on both glass/FTO and glass/FTO/CdS surfaces.

Plasmonic coupling at a metal/semiconductor interface

Integrating plasmonic nanoparticles with semiconductor substrates introduces strong optical resonances that extend and enhance the spectrum of photocatalytic and photovoltaic activity. The effect of plasmonic resonances has been variously attributed to the field nanoconfinement, plasmon–exciton coupling, hot electron transfer, and so on, based on action spectra of enhanced photoactivity. It remains unclear, however, whether energized carriers in the substrate are generated by the transfer of plasmonically generated hot electrons from the metal, as broadly believed, or directly by dephasing of the plasmonic field at the interface. Here, we demonstrate the importance of the direct plasmonic coupling across the chemical interface for hot electron generation at a prototypical Ag nanocluster/TiO2 heterojunction by direct probing of the coherence and hot electron dynamics with two-photon photoemission spectroscopy. Energy, time and material distributions of excitations in the Ag nanocluster/TiO2 heterojunction indicate that dielectric coupling with the substrate renormalizes the plasmon resonance of the Ag nanoparticle, and its dephasing directly generates hot electrons in TiO2 on a <10 fs timescale.

Experimental investigation of photocatalytic and photovoltaic activity of titania/rice husk crystalline nano-silica hybrid composite

As a kind of highly operative, stable photocatalysts and low‐cost, TiO2 has received significant scientific attention. However, it can only be initiated under ultraviolet light irradiation owing to its wide bandgap, weak separation efficiency of carriers and high recombination. Doping or making composites is an active method to outspread the light absorption to the visible light region. This article describes the extraction procedure of nano-silica from rice husk through a dissolution-precipitation process and producing titania-nanosilica composites by sol-gel method for photocatalytic and photovoltaic application where extracted nanosilica act as green filler to enhance the surface area of titania photocatalyst and an inhibitor of recombination. Our general plans are anticipated by passivated composite to enhance the activity of TiO2 semiconductors. This results show that the TiO2 /rice husk extracted crystalline nanosilica (RHCNS) has formed an active hybrid photocatalyst which is significant for photovoltaics application also. Large enhancement of photovoltaic parameters and rate of dye degradation of the TiO2/RHCNS composite observed which is stepping path to further development in adsorption-assisted photocatalysts under both UV and visible lights.

Predicting hidden bulk phases from surface phases in bilayered Sr3Ru2O7

The ability to predict hidden phases under extreme conditions is not only crucial to understanding and manipulating materials but it could also lead to insight into new phenomena and novel routes to synthesize new phases. This is especially true for Ruddlesden-Popper perovskite phases that possess interesting properties ranging from superconductivity and colossal magnetoresistance to photovoltaic and catalytic activities. In particular, the physical properties of the bilayer perovskite Sr3Ru2O7 at the surface are intimately tied to the rotation and tilt of the RuO6 octahedra. To take advantage of the extra degree of freedom associated with tilting we have performed first principles hybrid density functional simulations of uniaxial pressure applied along the c-axis of bulk Sr3Ru2O7 where we find that the octahedra become tilted, leading to two phase transitions. One is a structural transition at simeq 1.5 GPa, and the other is from a ferromagnetic (FM) metal to an antiferromagnetic (AFM) insulator at simeq 21 GPa whose AFM spin configuration is different from the AFM state near the FM ground state.

Thermally induced crystallization, hole-transport, NLO and photovoltaic activity of a bis-diarylamine-based push-pull molecule

The synthesis of a molecule constituted of two diarylamine-based push-pull chromophores covalently linked via their nitrogen atom is described. Comparison of the electronic properties with the parent monomer shows that dimerization has negligible influence on the electronic properties of the molecule but exerts a dramatic impact on the capacity of the material to self-reorganize. Application of thermal annealing to thin films induces the crystallization under original morphologies, a process accompanied by a partial bleaching of the absorption in the visible range and by a huge increase of hole-mobility. X-ray diffraction data on single crystals reveal the presence of π-stacked organization with a non-centrosymmetric co-facial arrangement of the dipoles which leads to intrinsic 2nd order bulk NLO properties of thin films as evidenced by second harmonic generation under 800 nm laser light. The implications of this thermally induced crystallization on the photovoltaic properties of the material are discussed on the basis of preliminary results obtained on simple bilayer organic solar cells.