Current Density-voltage Curves Research Articles

Improved performance of PCBM/MAPbI3 heterojunction photovoltaic cells with the treatment of a saturated BCP/IPA solution

The interfacial contact quality between the hydrophilic MAPbI 3 and hydrophobic PCBM thin films are improved by using the treatment of a saturated bathocuproine/isopropanol (BCP/IPA) solution, which largely increases the power conversion efficiency (PCE) from 12.96% to 18.67%. The atomic force microscopic images, water-droplet contact angle images, viscosity measurement results and near-infrared transmittance spectra show that the increased open-circuit voltage (V OC ) is related to the formation of a denser PCBM thin film and the better contact quality of the PCBM/MAPbI 3 heterojunction. Besides, the power-dependent current density-voltage (J-V) curves show that the lower defect density in the solar cells results in the higher V OC . In other words, the treatment of a saturated BCP/IPA solution can decrease the defect density of the PCBM/MAPbI 3 heterojunction and thereby boosting the photovoltaic performance and extending the device lifespan. • The saturated BCP/IPA solution treatment increases the density of the PCBM thin film. • The saturated BCP/IPA solution treatment strengthens the contact quality at PCBM/MAPbI 3 interface. • The saturated BCP/IPA solution treatment increases the hydrophobicity of PCBM/MAPbI 3 heterojunction. • The saturated BCP/IPA solution treatment improves the PCE of photovoltaic cells from 12.69% to 18.67%.

Van der Waals integration of GaN light-emitting diode arrays on foreign graphene films using semiconductor/graphene heterostructures

We report the van der Waals integration of micropatterned GaN light-emitting diodes (LEDs) onto foreign graphene films. GaN micro-LEDs were selectively grown on a graphene substrate using a patterned SiO2 mask, and then the whole device structure was laterally fixed by a polyimide insulator to form a united layer. After device fabrication, the LED/graphene heterostructure device was piled on the foreign graphene layers using a typical wet transfer technique of 2D crystals where the bottom graphene layer of the heterostructure was adhered to the foreign graphene only by van der Waals interactions. The transferred micro-LEDs showed well-aligned crystallographic orientations as well as reliable device performances, including strong light emissions, good rectifying behaviors of the current density–voltage curve, and good simultaneity between the electroluminescence intensity and the applied currents, ensuring reliable electrical connections and mechanical adhesions of the light-emitting layer to the foreign graphene films. Furthermore, the reliable adhesiveness allowed us to achieve device wearability, while the LEDs exhibited homogeneous light emissions under various bending conditions because of negligible external stress in the discrete micro-LEDs.

A Study on Epitaxial Lift-Off in InGaP/GaAs Double-Junction Solar Cells via Au-Au Bonding on Pre-Patterned Area

We have investigated the improvement of GaAs substrate reusing and the regrowth possibility of the epi-layer for the flexible InGaP/GaAs double junction solar cell. The presence of residues on the GaAs substrate surface separated by the epitaxial lift-off process is closely related to the regrowth of the epitaxial layer. A pre-patterning process was introduced to investigate the correlation between the lateral etch rate of the sacrificial layer and the generation of residues on the substrate. And the lateral etch rate was adjusted according to the changes in the pre-patterning area. The residues on surface of the GaAs substrate according to the lateral etch rate were observed by SEM/EDX. The structure of the InGaP/GaAs double junction solar cell re-grown on the GaAs substrate was measured by X-ray diffraction. The performance of the re-grown solar cell was measured by the current density-voltage curve at AM1.5G, 1sun with a solar simulator. The GaAs substrate was separated in the cleanest state by the pre-patterning area of 2 x 2mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the conversion efficiency of the re-grown solar cell by reusing this for three times was maintained similar to its conversion efficiency when a solar cell of initial growth.

NaCl 수용액 가습으로 인한 PEMFC 전기화학적 특성 연구

In this study, polymer electrolyte membrane fuel cells (PEMFCs) were humidified with NaCl solutions. NaCl solutions were provided to the cathode side of fuel cells by bubbling. De-Ionized water, 3.5 wt% NaCl solution, and 20 wt% NaCl solution were used to evaluate the effects of NaCl. Current density-voltage curves and electrochemical impedance spectroscopies (EIS) of fuel cells were measured. Additionally, the constant-voltage mode long-term stability of PEMFCs humidified with NaCl solution were investigated. Constant-voltage measurements and EIS results imply that the degradation of fuel cells is clearly related with the concentration of NaCl solutions.

Fabrication and characterization of micro-tubular solid oxide fuel cells with yttria stabilized zirconia and Hafnia-Erbia co-doped bismuth oxide bilayer electrolyte

Current solid oxide fuel cell (SOFC) technology relies on YSZ electrolyte material due to its high stability under SOFC operation conditions. However, the ionic conductivity of YSZ decays as the operation temperature decreases to intermediate or low-temperature range.Commercialization of SOFC systems is hindered by the high manufacturing cost, which is directly related to the use of special and expensive system components because of the high operating temperatures of SOFCs. It is possible to use low-cost materials in system production if the operating temperature of SOFCs is reduced below 600 °C.In this study, we investigated the possibility of using 8% mol Yttria stabilized Zirconia (YSZ) and Hafnia-Erbia Co-doped Bismuth Oxide (HEB, ((Er2O3)0.20(Bi2O3)0.80)0.99-(HfO2)0.01) bilayer electrolyte configuration to lower the operating temperatures of SOFC to 600 °C and below. The cell performances at low-temperature region (T < 600 °C) are aimed to be increased with the additional HEB layer by the increased oxygen reduction kinetics on the air electrolyte side.Using a combination of thermoplastic extrusion and dip coating processes, four distinct cell types were created. Cells with monolayer and bilayer electrolyte were generated for each cathode type using two different cathode types, Lanthanum Strontium Manganate (LSM) and LSM-HEB. On the cell performance and operating temperatures, the impacts of electrolyte configuration and cathode type were examined. It was also explored whether the HEB material would be more effective as a second electrolyte or as a composite cathode if it was added to the LSM. Under various cell operating circumstances (different oxygen partial pressure values), several cell parameters such as the ohmic resistance, exchange current density, and anodic and cathodic saturation current densities were derived by fitting the experimentally recorded current density–voltage curves into the polarization model. The polarization resistances were calculated using cell parameters and four different cells were compared with each other. The performances measurements of both cell configurations showed that the peak power density of the bi-layered electrolyte configuration improved by a factor of 1.45 and reached 0.94 W/cm2 at 600 °C, while it was only 0.51 W/cm2 for the monolayered YSZ electrolyte configuration. Additionally, the effect of HEB addition to LSM cathode resulted in a performance increase of %84 compared to the cell with LSM cathode only. The presence of HEB either as a second electrolyte or ionic conductive phase in the composite cathode is lowered activation polarization of the cells both bi- or monolayered electrolyte cells and resulted in increased performance.

Growth of MoS2 and metal back electrode-dependent performance of MoS2/Si heterojunction solar cells

In this work, MoS2 thin films were successfully synthesized by chemical vapor deposition (CVD) using MoO3 and sulfur powders as precursor sources. The effect of the MoO3 dosage and heating temperature on the quality of the synthesized MoS2 films are investigated and a detailed reaction mechanism is proposed to interpret the obtained experimental result. Furthermore, we have studied the influence of different metal back electrodes (including Ag and Au) on the photovoltaic performance of the fabricated MoS2/Si heterojunction solar cell. It is shown that, in comparison with the solar cell using Au as a metal back electrode, the solar cell using Ag as a metal back electrode has poor photovoltaic performance with the appearance of the S-type shape in the measured current density-voltage curve. Finally, numerical simulation based on AFORS-HET software has been carried out to investigate the photovoltaic performance of the [Formula: see text]-MoS2/[Formula: see text]-Si heterojunction solar cell under different work functions of the metal back electrode. The result of numerical simulation is consistent with our experiential result in the trend. This work is highly relevant to the development of transition metal dichalcogenides in the application of solar cells.

Effect of anatase-rutile phase ratio of titania photoanode on photoelectrochemical performance and photoconversion efficiency

Modification of photoanode is an emerging technique to achieve improved photoconversion efficiency in Dye Sensitized Solar Cells (DSSCs). Many strategies have been used to improve the performance of the popular photoanode material, TiO2. The current study reports the role of the anatase/rutile (A/R) ratio of titania photoanodes on the charge transport properties and photoconversion efficiency (PCE). A/R ratio of the photoanodes was varied by modifying Degussa P25 (DP25). The A/R ratio of the photoanodes was calculated through structural analyses. The varying charge transfer resistance (Rct) calculated from impedance analyses confirmed the influence of A/R ratio on the charge transfer properties, while the morphology of the photoanodes was not affected as per FESEM results. Current Density-Voltage (J-V) curves of the fabricated DSSCs show the effect of A/R ratio on the photoconversion performance of the photoanodes. The DSSC with photoanode having A/R ratio of 1.44 showed the highest PCE compared to the rest of the photoanodes and which is in accordance with the EIS results. This study reveals the role of A/R ratio on the charge transport properties of titania and photoconversion efficiency of the fabricated DSSCs.

Synthesis of titanium dioxide nanorods combining with titanium dioxide nanoparticles/reduced graphene oxide nanocomposite for fabrication of photoanodes in dye–sensitized solar cells

ABSTRACT Titanium dioxide nanoparticles/reduced graphene oxide nanocomposite (TG) was synthesised by ex situ method. The obtained nanocomposite was screen–printed onto surface modified fluorine-doped tin oxide (FTO) plates with titanium dioxide nanorods (TNRs) to prepare dye–sensitised solar cells (DSSCs). The electrochemical properties of as-prepared photoanodes were analysed via current density–voltage curves and electrochemical impedance spectroscopy. Characterisation of TG was measured by modern analytical methods. Results indicated that the DSSCs reached an efficiency of 6.76% with 1 wt.% content of graphene oxide (GO) precursor, higher than that of commercial titanium dioxide nanoparticles (TNPs) photoanodes. Furthermore, transmission electron microscopy images demonstrated that TNPs with a diameter of 20–25 nm were well distributed on reduced graphene oxide (rGO) sheets. TNRs exhibited lengths in the range of 2.7 to 3.0 µm and an average diameter of 0.7 µm. The TNRs combining TG demonstrated potential in improving DSSCs efficiency.

UV and Visible Photodetectors of MAPbBr3 and MAPbCl3 Perovskite Single Crystals via Single Photocarrier Transport Design

AbstractUnderstanding photogenerated charge transport is critical to further improving the performance of perovskite‐based devices. In this study, the low‐defect perovskite CH3NH3PbX3 (X = Br or Cl) single crystals, which are an ideal platform for high‐quality optoelectronic devices, are fabricated to examine characteristics of photodetectors with electrodes with Au or Ag, and interlayer of TiO2. The transport mechanism of the photogenerated carriers in each device is elucidated by analysis of the current density–voltage curves under dark or a 405 nm of super‐bandgap illumination or a 640 nm of sub‐bandgap illumination. The photocurrent under the 405 nm illumination is improved under the hole‐dominant Au‐device of p‐type bromide crystals and the electron‐dominant Ag‐device of n‐type chloride crystals. The defect‐assisted excitation under 640 nm illumination is associated with generation of the holes with the defects located near the conduction band or the electrons with the valence band in each perovskite materials. With this conception, the responsivity of 0.07 A W−1, specific detectivity over 1011 Jones, and external quantum efficiency around 16% are obtained in the best performing devices. The present results suggest a promising strategy for designing efficient photodetectors using photogenerated and trap‐assisted photocarriers that contribute to enhanced photocurrent.

Device modelling and optimization studies on novel ITIC-OE based non-fullerene organic solar cell with diverse hole and electron transport layers

The novel fullerene-free organic solar cell with high dielectric constant ITIC-OE acceptor material shows a lot of potential for advancements in organic photovoltaics research. In this work, organic bulk heterojunction solar cell with polymer donor PBDB-T and non-fullerene acceptor ITIC-OE is studied in detail using SCAPS 1-D. The software is calibrated by matching the simulated J-V(current density-voltage) curve and EQE(External quantum efficiency) curve measurements with the experimental results for the primary solar cell structure ITO/PEDOT:PSS/PBDB-T/ITIC-OE/PFN-Br/Ag. Different hole and electron transport layer(HTL and ETL) candidates are simulated to study the cell performance. The proposed candidates for HTL are Copper iodide(CuI),Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS), Nickel oxide(NiO) and Poly[2- methoxy-5-(2-ethyl hexyloxy) −1, 4- phenylene vinylene] (MEH-PPV) while that for ETL are Titanium dioxide (TiO2), Zinc oxide(ZnO), Phenyl- C61 -butyric acid methyl ester (PCBM), C60, Poly(9,9-bis(3’-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide (PFN–Br), Indium gallium zinc oxide (IGZO) and Tin dioxide (SnO2) respectively. Among the various combinations, NiO(nickel oxide) as HTL and TiO2 (titanium dioxide) as ETL delivers the highest output. The design is further optimized to study the effect of material parameters on the device performance.

Electronic Parameters of Diode Based Organometallic Semiconductor Dyes Centered Ruthenium Complexes with Active COOH Terminals.

In this study, the ruthenium complexes, which is an organometallic N-3 and C-106 semiconductor material, was coated on indium tin oxide (ITO) by using the self-assembled technique and thus a diode containing an organometallic interface was produced. The effects of this interface on the electronic parameters of the diode were investigated. It is aimed to improve the heterogeneity problem of the inorganic/organic interface by chemically bonding these materials from COOH active parts to the ITO surface. In order to understand how the electronic parameters of the diode change with this modification, the Schottky diode electrical characterization approach has been used. The charge mobility of the diode was calculated using the current density-voltage curve (J-V) characteristic with Space Charge Limited Current (SCLC) technique. When the electrical field is applied to the diode, it can be said that the ruthenium complexes molecules create an electrical dipole and the tunneling current is transferred to the anode contact ITO through the ruthenium molecule through the charge carrier, thus contributing to the hole injection. The morphology of these interface modifications was examined by Atomic Force Microscope (AFM) and surface potential energy by KelvinProbe Force Microscope (KPFM). To investigate local conductivity of bare ITO and modified ITO surface, Scanning Spreading Resistance Microscopy (SSRM) that is a conductive AFM analyzing technique were performed by applying voltage to the conductive tip and to the sample. According to the results of this work the diode containing N-3 material shows the best performance in terms of charge injection to the ITO due to possess the lowest barrier height Φb as 0.43 eV.

Comprehensive device simulation of 16.9% efficient two-terminal PbS–PbS CQD tandem solar cell

The significant losses that limit the efficiency of a single-junction solar cell are thermalization loss and transmission loss. Thus, to efficiently utilize the solar spectrum and mitigate these losses, tandem solar cells (TSCs) have significantly impacted the photovoltaic (PV) landscape. In this context, the research on perovskite/silicon tandems is currently dominating the research community. However, challenges such as stability of perovskite, pin-hole defects, conformal deposition of perovskite over textured silicon, the low absorption coefficient of silicon, and high module cost of the bottom subcell are the tailback for its mass production at the industrial level. Therefore, considering the detailed balance limit for the TSC, a low-cost solution-processed top and bottom subcells with a tunable bandgap can be well thought for the low-cost tandem design. Thus, here in this work, two different PbS–PbS colloidal quantum dot (CQD) TSCs with a conversion efficiency of 15.6% and 16.9% are proposed through comprehensive device simulations. Three different PbS-CQDs with a bandgap of 1.14eV, 1.45eV, and 1.56eV are utilized to design the TSCs under consideration. Detailed standalone and tandem analysis has been carried out in terms of absorber layer thickness variation, filtered spectrum, filtered integrated power, current matching, tandem current density voltage (J-V) curves, and tandem PV parameter to finalize the conversion efficiency. The filtered spectrums are obtained by using the transfer matrix method to account for the interfacial reflection losses and thin-film interference effects. The tandem device constructed using 1.45eV and 1.56eV based top subcell showed the open-circuit voltage V OC of as high as 1.71V and 1.83V, respectively. The comprehensive theoretical analysis of PbS–PbS CQD tandem devices proposed in this work may pave the way for developing high-efficiency TSCs for low-cost applications. • Two different PbS–PbS CQDs tandem solar cells (TSCs) with a conversion efficiency of 15.60% and 16.92% are proposed. • Detailed standalone and tandem analysis has been carried out to optimize the conversion efficiency. • Three different PbS-CQDs with a bandgap of 1.14eV, 1.45eV, and 1.56eV are utilized to design the TSCs under consideration. • TSCs constructed using 1.45eV and 1.56eV based top subcell showed the open-circuit voltage V OC of 1.71V and 1.83V, respectively. • This detailed study would open path for development of high-efficiency, low-cost perovskite-PbS CQD TSCs in future.

Growth of ZnO/Bi2S3 electron transport layer films to improve the efficiency and stability of organic solar cells

Zinc oxide (ZnO) grown on indium tin oxide (ITO) glass substrates were decorated with bismuth sulfide (Bi2S3) nanorods by thermal decomposition of bismuth ethylxanthate precursor method. Different thicknesses of ZnO/Bi2S3 bilayer films were prepared by controlling the spin speed of bismuth xanthate precursors (5000, 6000 and 7000 rpm, respectively) and applied as the electron transport layer (ETL) in organic solar cells (OSCs) with the structure of ITO/ZnO/Bi2S3/PM6:Y6/MoO3/Ag. The effects of different thickness of ZnO/Bi2S3 as ETLs on device performance and stability were investigated in detail. Firstly, the device based on ZnO/Bi2S3 6000 rpm as ETL confirmed excellent performance with the power conversion efficiency (PCE) of 12.50%, which was improved by 28.60% of the reference device without Bi2S3 nanorods coated. XRD and SEM results showed that Bi2S3 nanorods covered the ZnO surface well. Electrical conductivity and the current density-voltage (J-V) curve results under dark conditions showed that when Bi2S3 nanorods were added between the active layer and ZnO, the interfacial conductivity can be effectively increased and improved the interfacial carrier transport efficiency. Secondly, the stability results of the ZnO/Bi2S3 6000 rpm device demonstrated that the PCE of ZnO/Bi2S3 6000 rpm device was maintained about 91.54%, while that of pure ZnO as ETL was maintained about 75.26% of the original value after 33 h in air. This means that the ZnO/Bi2S3 prepared by thermal decomposition of the bismuth xanthate precursor on ZnO is a promising electron transport material in OSCs.

Air-stable synthesis of near-infrared AgInSe2 quantum dots for sensitized solar cells

The synthesis of highly photoluminescent quantum dots (QDs) is critical for QD sensitized solar cells. As a typical I-III-VI compound, AgInSe2 QDs with high quality were often synthesized by the hot-injection method with a stock solution of selenium powder in oleylamine, trioctylphosphine used as capping agent. This work introduces selenium dioxide as a selenium source to synthesize high-quality AglnSe2 with the tunable composition by a heating-up method in air. The gradient compositions of AglnSe2 QDs were achieved by the control of the relative feeding ratio of Ag/In precursors. The emission peaks of AglnSe2 QDs locate between 740 ~ 1080 nm with as longer lifetime as 450 ns, depending on the ratio of Ag/In in AgInSe2. The ligand exchange was adapted to assist adsorption onto the TiO2 photoanode. Under a complete solar illumination, AgInSe2 QDs-sensitized solar cells demonstrated the best power conversion efficiency of 3.31%. The current density-voltage curves of the best solar cells showed that the short circuit current was 18.16 mA.cm−2, the open-circuit voltage was 0.35 V, and the fill factor was 51%. The improved photoelectric performance of the AglnSe2 QD is thought as the attribution of theirs enhanced PL lifetime and broader spectral response reaching 1100 nm. This method proposes a new strategy for the synthesis of AglnSe2 QDs with high quality.

Synthesis of titanium dioxide/reduced graphene oxide nanocomposite material via the incorporated hydrothermal co-precipitation method for fabricating photoanode in dye-sensitized solar cell

This study first investigates the preparation and characterization of titanium dioxide/reduced graphene oxide (TiO2/rGO) and then proposes the fabrication of photoanode in dye-sensitized solar cell (DSSC) from synthesized materials. Herein, the TiO2/rGO nanocomposites were prepared by the incorporation of hydrothermal approach and co-precipitation method from the precursors of titanium (IV) isopropoxide and graphene oxide. The fabrication of photoanode from the as-prepared TiO2/rGO nanocomposite paste was carried out using screen-printing technique. The performance of fabricated DSSCs was evaluated by current density-voltage curves and electrochemical impedance spectroscopy. The characterizations of TiO2 nanoparticles, TiO2/rGO nanocomposites, and their precursors were confirmed by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. Experimental data showed that the optimal rGO weight percentage of 0.6% in the TiO2/rGO nanocomposite material fabricated DSSC successfully with the highest values of short-circuit current density (17.65 mA/cm2) and energy conversion efficiency (7.46%), approximately increasing 24% and 25%, respectively, in comparison with the pristine TiO2 material. Characterization results indicated that the incorporated hydrothermal co-precipitation method was efficient in producing well-defined spherical TiO2 nanoparticles decorated on the rGO sheets with an average diameter of 20–25 nm. Therefore, the TiO2/rGO nanocomposites with the eco-friendly and efficient synthesis method are highly promising for manufacturing and commercializing DSSCs widely.

Copper nanoparticle-decorated RGO electrodes as hole transport layer of perovskite solar cells enhancing efficiency and shelf stability

In this work, we explore the addition of reduced graphene oxide (RGO) decorated with copper ([email protected]) as hole transport layer (HTL) into carbon/CH3NH3PbI3/TiO2/FTO perovskite solar cell (PSC). Numerous instrumentations characterized the fabricated composites. The deposited Cu on RGO showed spherical metallic particles with diameters of 22–30 nm. Current density–voltage curves and Incident photon-to-electron conversion explore the impact of [email protected] on the photoconversion efficiency (PCE). The fashioned [email protected] nanocomposite showed improved PCE at 13.55% compared to 11.3 and 5.5% for the PSCs with [email protected] and pure RGO as HTL, respectively. These impacts are due to the significant hole extraction that proved by the photoluminescence quenching. Moreover, the produced devices with [email protected] displayed shelf stability at 88.8% of its initial PCE after two months. This work marks an important milestone towards the development of solar cells with reliable and high-performance perovskites.

Efficient and Economically Favorable Co-Free Air Electrodes for Solid Oxide Cells

Cobalt-based oxides are considered as state-of-the-art air electrode materials for solid oxide cells (SOC). It is due to their extraordinary catalytic activity and high mixed ionic-electronic conductivity. However, geo-politically unstable regions which supply cobalt (approx. 70% global mining production in 2018 took place in the Democratic Republic of the Congo), depleting reserves and the forecasted continuously growing demand for the element in next decades (related to the Li-ion batteries market) may result in risks related to the security of supply. Due to mentioned considerations, in 2011 cobalt was classified by EU as a critical raw material [1]. For that reason, European Commission provide incentives for the development of Co-free air electrodes which will eliminate the aforementioned risks and also address the toxicity of cobalt. Moreover, special attention is paid to the socio-economic aspects related to its mining which often does not meet global standards related to the ethical supply of the element.Among proposed in literature air electrodes dedicated both solid oxide fuel cells (SOFC) and solid oxide electrolyzers (SOE) the La(Ni,Cu)O3-δ-based materials seem to be a promising and economically viable alternative. Alike cobalt, nickel and copper are of great economic importance, however they are not considered as critical raw materials and, what is worth to emphasize, can be effectively recycled without compromising the quality. Parent LaNiO3 and LaCuO3 perovskites are characterized by a set of beneficial physicochemical properties, including high electric conductivity, which in the case of LaCuO3 reaches 106 S cm-1 in an oxidizing atmosphere, large range of oxygen nonstoichiometry (up to 0.5 mol per mol of oxide) as well as high catalytic activity [2,3]. As we presented in [4] mixed Ni-Cu perovskites are stable in air while exposed to the temperature up to 900 °C, and only in the case of Cu-rich composition, 0.75 mol Cu per mol of La(Ni,Cu)O3-δ, phase-transition from P4/m to P4/mbm symmetry was recorded. Comparing to the Co-based materials La(Ni,Cu)O3-δ oxides demonstrate moderate TEC in the range from 10 to 14·10-6 K-1. This feature should provide a good thermomechanical compatibility with CGD buffer layer deposited on the 8YSZ electrolyte. LaNi0.5Cu0.5O3-δ and LaNi0.25Cu0.75O3-δ oxides are characterized by a large variation of oxygen nonstoichiometry (up to 0.15 mol of oxygen per oxide at 850 °C) and relatively high electrical conductivity (order of several dozen). The electrodes based on these oxides show low polarization resistance in air at 800 °C equal to 0.056 Ω cm2 and 0.054 Ω cm2 for LaNi0.5Cu0.5O3-δ and LaNi0.25Cu0.75O3-δ, respectively. Preliminary studies of the LSGM-supported full cell with LaNi0.5Cu0.5O3-δ as air electrode (0.87 W cm-2 in SOFC mode and ca. 1 A cm-1 at 1.3 V in SOE mode at 900 °C) revealed potential of (Ni,Cu)-based perovskite in application as an electrode for reversible solid oxide cells (rSOC).In this work the assessment of (Ni-Cu)-based perovskites in terms of the availability of critical raw materials, sustainability and economic aspect in relation to the Co-based oxides is presented. Moreover, the electrochemical studies of fuel electrode-supported cells with selected La(Ni,Cu)O3-δ materials making the air electrodes are presented. LaNi0.5Cu0.5O3-δ and LaNi0.25Cu0.75O3-δ made using sol-gel method were used to fabricate air electrodes layers sintered at relatively low temperature (below 1,000 °C) and characterized by fine microstructure allowing sufficient gas diffusion. The electrochemical measurements included current density-voltage curves, registered in SOFC and SOE modes, and EIS studies performed at different condition (temperature in the 700-800 °C range and various inlet gases composition).

Efficient and Economically Favorable Co-Free Air Electrodes for Solid Oxide Cells

In this work, the assessment of LaNi0.5Cu0.5O3-δ-based perovskite in terms of the availability of critical raw materials, sustainability, and economic aspect in relation to the Co-based oxides is presented. Chemical compatibility between LaNi0.5Cu0.5O3-δ, obtained by the sol-gel method, and commercial CGO powder is evaluated. Moreover, the electrochemical studies of fuel electrode-supported cells with LaNi0.5Cu0.5O3-δ material as the air electrodes are presented. The electrochemical measurements - current density-voltage curves, were measured at different conditions including temperature in the 700-800 °C range and variation of the composition of feeding gases.

Ambient processed perovskite sensitized porous TiO2 nanorods for highly efficient and stable perovskite solar cells

One dimensional (1-D) TiO2 nanorod (NR) scaffold layers are considered to be a superior electron transporting layer (ETL) for perovskite solar cells (PSC) as compared to TiO2 nanoparticles (NP) in relation of morphological and electronic properties. Rutile phase porous TiO2-NR has been grown with different lengths and porosity via the hydrothermal method. Porosity and length of the rods are controlled by varying the reaction time and concentration of the precursor solution. Change in the morphology and their effect on the photovoltaic and charge transport properties are investigated deeply through scanning electron microscopy, current density voltage (J-V) curves and electrochemical impedance spectroscopy (EIS). The synthesized TiO2-NR and NP-TiO2 electrodes are used to fabricate ambient processed PSCs. Compared to the conventional NP-TiO2 based PSC device, the device is prepared with the 350 nm porous TiO2-NR has shown improved power conversion efficiency (14.0%). Such enhancement in photovoltaic performance arises from uniform infiltration of perovskite into the scaffold layer, which enhances the light collection efficiency and increases electron-transport property. Furthermore, the NR based PSC devices have retained 80% of its initial performance even after 50 days of being stored in ambient conditions (relative humidity (RH) - 60%). These results further emphasize the use of 1-D NR as ETL for ambient processed PSC with improved stability.

Improving the performance of OLEDs by controlling the molecular orientation in charge carrier transport layers.

The transition dipole moment (TDM) orientation in the emission layer (EML) of organic light-emitting diodes (OLEDs) have attracted increasing attention from many researchers. But the study point at the molecular orientation in the hole transport layer (HTL) and electron transport layer (ETL) was not reported widely. In this paper, the molecular orientation of HTLs and ETLs were controlled by the deposition rate. The angle-dependent PL spectra and the variable angle spectroscopic ellipsometry (VASE) were used for evaluating the molecular orientation of B3PYMPM and TAPC, respectively. We found that fast deposition rate can boost preferentially vertical molecular orientation in both molecules and facilitate the hole and electron mobility, which was tested by the current density-voltage and capacitance-voltage curves of HODs and EODs. Moreover, the HTLs and ETLs were employed in OLED devices to verify the influence of molecular orientation on charge carrier mobility, which determined the performance of OLEDs significantly.