Improvement Of Long-term Stability Research Articles

Cesium[sbnd]lead based inorganic perovskite quantum-dots as interfacial layer for highly stable perovskite solar cells with exceeding 21% efficiency

Despite the excellent photovoltaic performances of perovskite solar cells (PSCs), the instability of PSCs under severe environment (e.g. humidity, light-induced, etc.) limits further commercialization of such devices. Therefore, in recent years, research on the long-term stability improvement of PSCs has been actively carried out in perovskite field. To address these issues, we demonstrated the incorporation of ultra-thin interfacial layer of inorganic CsPbBr1.85I1.15 perovskite quantum-dots (PQDs) that can effectively passivate defects at or near to the perovskite/hole transport material (HTM) interface, significantly suppressing interfacial recombination. This passivation layer increased the open circuit voltage (Voc) of triple-cation perovskite cells by as much as 50 mV, with champion cells achieving Voc ∼ 1.14 V. As a result, we obtained hysteresis-free cells with the efficiency beyond 21%. More importantly, devices based on such architecture are capable of resisting humidity and light-induced. Remarkably, the device employing CsPbBr1.85I1.15 demonstrated a superb shelf-stability aganist to humidity under ambient conditions (R.H.≥40%), retaining nearly 91% of initial efficiency after 30 days, while the efficiency of control device rapidly dropped to 45% from its initial value under the same conditions. Besides benefiting from the high moisture resistivity as well as supressed ion migration, PSCs based on PQDs showed better operational stability (retaining 94% of their initial performance) than that of the PQDs-free one under continuous light irradiation over 400 h. In addition, a faster PL decay time of 4.66 ns was attained for perovskite/PQDs structure (5.77 ns for only PQDs structure) due to the favorable energy transfer at the interface, indicating a Förster resonance energy transfer (FRET) mechanism. This work indicates that inorganic PQDs are important materials as interlayer in PSCs to supremely enhance the device stability and efficiency.

Dopant-Free Hole-Transporting Polymers for Efficient and Stable Perovskite Solar Cells

A series of novel polymers (P1–P6) derived from the combination of different units (including thiophene, triarylamine, and spirobifluorene) were successfully synthesized, completely characterized, and used as hole-transporting materials (HTMs) for perovskite solar cells (PSCs). Solar cells with some of these materials as HTMs showed very good performances of almost 13% (12.75% for P4 and 12.38% for P6) even without additives, and devices based on these new HTMs show relatively improved stability against temperature compared to those based on PTAA. The presence of dopant additives has been linked to long-term degradation, which is the main barrier to the large-scale commercialization of this innovative type of solar cell. Obtaining efficient PSCs without using dopants could represent a further step toward improvement of long-term stability and thus their introduction into the market.

Solid-phase hot-pressing of POMs-ZIFs precursor and derived phosphide for overall water splitting

Rational design of electrocatalyst with high performance for both hydrogen and oxygen evolution reaction is attracting considerable attention in recent years. However, most electrocatalysts are powders and require to deposit on conductive substrates with binders, leading to complicated steps and hindering the improvement of long-term stability. This work exhibits a solid-phase hot-pressing method to prepare polyoxometalates based zeolitic imidazolate frameworks (POMs-ZIFs) precursor on carbon cloth (CC) rapidly and mildly. After phosphidation treatment, nitrogen-doped graphitic carbon layers coated phosphide on CC (CoP/MoP@NC/CC) is synthesized. CoP/MoP@NC/CC has excellent electrocatalytic performance for water splitting due to the synergistic effect of CoP, MoP and as-formed oxide/hydroxide layers. It shows the low overpotentials of 94 mV for HER and 270 mV for OER at the current density of 10 mA cm−2 in alkaline medium, which is superior to most of the reported phosphide-based electrocatalysts. Notably, the ultra-high current density of 1000 mA cm−2 can be reached at the overpotentials of only 475 mV for HER and 657 mV for OER. As both cathode and anode for overall water splitting, CoP/MoP@NC can achieve the current density of 50 mA cm−2 at the cell voltage of 1.71 V. The solid-phase hot-pressing method ensures the tight and uniform growth of the fast nucleating and stable materials on substrate and applies for more electrochemical reactions.

High performing AgNW transparent conducting electrodes with a sheet resistance of 2.5 Ω Sq-1 based upon a roll-to-roll compatible post-processing technique.

A report of transparent and conducting silver nanowires (AgNWs) that produce remarkable electrical performance, surface planarity and environmental stability is given. This research presents an innovative process that relies on three sequential steps, which are roll-to-roll (R2R) compatible: thermal embossing, infrared sintering and plasma treatment. This process leads to the demonstration of a conductive film with a sheet resistance of 2.5 Ω sq-1 and high transmittance, thus demonstrating the highest reported figure-of-merit in AgNWs to date (FoM = 933). A further benefit of the process is that the surface roughness is substantially reduced compared to traditional AgNW processing techniques. The consideration of the long-term stability is given by developing an accelerated life test process that simultaneously stresses the applied bias and temperature. Regression line fitting shows that a ∼150-times improvement in stability is achieved under 'normal operational conditions' when compared to traditionally deposited AgNW films. X-ray photoelectron spectroscopy (XPS) is used to understand the root cause of the improvement in long-term stability, which is related to reduced chemical changes in the AgNWs.

Improvement of long-term stability of hollow-core photonic-crystal fiber optic gyro based on single-polarization resonator.

To improve long-term stability, we present a single-polarization resonator optic gyro based on a hollow-core photonic-crystal fiber (HCPCF), utilizing a micro-optical polarizing coupler formed by pairs of collimators and a series of polarization-dependent devices. We build the mathematical model of the polarization noise of the proposed gyro and experimentally validate the elimination of the undesired polarization eigenstate, which is the basis of the system's improved long-term stability. We use multi-modulation to suppress the backscattering noise and the closed-loop detection method to eliminate the effect of fluctuating output power on the gyro bias. A long-term bias stability of 20°/h is successfully demonstrated.

The durability study of thermochromic vanadium dioxide films with the addition of barrier coatings

The high-performance thermochromic vanadium dioxide (VO2) films can be applied in many industrial applications such as smart windows, infrared sensors, and infrared imaging (bolometers). The preservation of its highly thermochromic properties of VO2 films is crucial since the oxidation number of vanadium ranges from +2 to +5 under various reducing or oxidizing atmospheres at elevated temperatures and humid environment. In this study, VO2 films were fabricated by thermal oxidation of co-sputtered thin films of vanadium and stainless-steel (SS), followed by the addition of barrier coatings on top of the as-prepared VO2 films for the improvement of long-term stability. The samples with barrier coatings containing zinc oxide (ZnO) and silicon oxide (SiO2) showed significantly better durability in either wet or dry high temperature environment. With an equivalent barrier coating thicknesses, the stability of the samples was ranked in the order of TiO2/ZnO/VO2:SS ∼ ZnO/SiO2/VO2:SS > VO2:SS > TiO2/SiO2/VO2:SS > Plain VO2 at wet condition (95% RH, 80 °C). In addition, the durability order was: TiO2/ZnO/VO2:SS > ZnO/SiO2/VO2:SS ∼ TiO2/SiO2/VO2:SS > VO2:SS > Plain VO2 at dry condition (300 °C). The results suggest that the proposed VO2/TiO2/ZnO barrier coating is a promising material for both durability and thermochromic performance.

Reduction of far off-resonance laser frequency drifts based on the second harmonic of electro-optic modulator detection in the optically pumped magnetometer.

The frequency drifts of the probe laser could be coupled into the calibrated scale factor of the optically pumped magnetometer (OPM) and induce an error of the measurement accuracy. We propose a method to reduce the far off-resonance laser frequency drifts based on the second harmonic of the electro-optic modulator (EOM) detection system in the all-optical K-Rb hybrid pumping magnetometer. Adopting the closed-loop feedback by monitoring the second-harmonic component in real time, the frequency drift of the probe laser has been effectively reduced by about five times to ∼30 MHz/0.5 h at the detuning of 130 GHz and the cell temperature of 443 K. Besides, this technique has been demonstrated to be helpful for reducing the frequency drifts at different detuning points and temperatures. This method is not only suitable for the development of more compact, high-sensitivity OPMs due to the long-term stability improvement with no extra optical path, but also can be applied to other atomic devices and EOM detection systems for reducing the influence of the laser.

Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La0.6Sr0.4Co0.2Fe0.8O3-δ versus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathode powders were obtained from solution combustion synthesis, deposited onto Ce0.8Sm0.2O2-δ electrolytes and eventually infiltrated with a La0.8Sr0.2MnO3-δ (LSM) nanosized discrete layer. The two half-cell systems were compared to evaluate the influence of infiltration, overpotential and ageing on their performance and stability. Structure, microstructure and chemical composition were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray spectroscopy (EDX), whereas redox behavior was evaluated through temperature programmed reduction (TPR) and thermal gravimetric analysis (TGA) in combination with electrochemical impedance spectroscopy (EIS), which was also used to test the electrochemical performance. A decrease of polarization resistance for both infiltrated electrodes, compared to the reference ones, was highlighted at open circuit voltage (OCV), although the BSCF-based cathode was more benefitted more from infiltration than the LSCF-based one. Moreover, the application of cathodic overpotentials (−0.1 to −0.3 V) resulted in opposite effects on the LSCF- and BSCF-based cathodes, highlighting a different response of the oxygen vacancies to the applied voltage for the two perovskite compositions. The positive effect of the LSM layer was further confirmed by the observed improvement in long-term stability of both infiltrated perovskite-type systems.

(Invited) Parallelized Nano-Pillar Perovskites for Semitransparent Solar Cells Using Anodized Aluminum Oxide Scaffold

Semitransparent solar cells have attracted significant attention for practical applications, such as windows in buildings and automobiles. Here, we report semitransparent, highly efficient, one-dimensionally nano-structured perovskite solar cells employing anodized aluminium oxide (AAO) as a scaffold layer. The parallel nano-pillars in the perovskite layer enable construction of haze-free semitransparent devices without any hysteresis behaviour. By controlling the pore size in the AAO, the volume occupied by the perovskite layer can be precisely varied, and the colour neutrality of the resulting devices can be achieved. With the incorporation of a transparent cathodic electrode (indium tin oxide, ITO) with a buffer layer (MoOx), a highly efficient semitransparent nano-pillared perovskite solar cell is achievable with a power-conversion efficiency of 9.6% (7.5%) and a whole device average visible light transmittance of 29.7% (38.2%). To determine the role of the scaffold layer in improving the photo-electrical properties of the cell, impedance spectroscopy analyses were performed, revealing that the AAO-structured perovskite layer suppresses internal ion diffusion and enables critical improvements in long-term stability under continuous illumination.

A Novel Poly(acrylonitrile)-Based Quasi-Solid-State Electrolyte for Dye-Sensitized Solar Cells

The use of volatile liquid electrolytes limits the practical application of dye-sensitized solar cells (DSSCs) because of stability issues. Gel-type electrolytes have shown promising results in terms of cell stability and efficiency. Poly(acrylonitrile) has been known for its high ion solvation ability and structural stability.1 Herein, we report a quasi-solid-state DSSCs (QS-DSSCs) using gel polymer electrolyte (GPE) based on poly( acrylonitrile-co-methyl acrylate) (i.e. P(AN-co-MA)) dissolving a iodide-acetonitrile solution. The MA group rotates freely on the polymer chain to effectively coordinate the electrolyte solution into the polymer matrix.2By adjusting the polymer content, we can control the gelation time of the GPE for smooth electrolyte injection into the cells. No filler is needed to expedite the gelation process. The QS-DSSCs exhibit higher short-circuit currents than liquid-state DSSCs (L-DSSCs). The polymer chains may have adhered to the TiO2films in the QS-DSSCs to suppress charge leakage and promote the photocurrent. However, the QS-DSSCs have smaller fill factors than the L-DSSCs, likely due to lower ionic conductivity of the GPE relative to the liquid electrolyte. Using the N719 dye as the sensitizer, the QS-DSSCs have a power conversion efficiency of 9.5 % whereas the L-DSSCs show a similar efficiency of 9.6 %. Importantly, the proposed QS-DSSCs presented considerable improvements in long-term stability when subjected to accelerated aging. This developed GPE has presented a promising potential to replace liquid-state electrolytes used in DSSCs.

1,2,3-Triazolium-Based Poly(2,6-Dimethyl Phenylene Oxide) Copolymers as Anion Exchange Membranes.

Anion exchange membranes (AEMs) based on 1,2,3-triazolium (TAM) were prepared from commercial poly(2,6-dimethyl phenylene oxide) (PPO) via "click chemistry" and subsequent N-alkylation. Flexible and tough membranes with various ion exchange capacities (IECs) were obtained by casting the polymers from NMP solutions. Although the resulting TAM-functionalized PPOs (PPO-TAM) membranes exhibited incomplete ion exchange in 1 M NaOH or NaHCO3 for 24 h even at elevated temperature, the highest hydroxide conductivities of the membranes were above 20 mS/cm at room temperature, which is comparable to many reported AEMs. Alkaline stability tests indicate that the PPO-TAM membranes showed a better alkaline stability than that of membranes containing imidazolium groups in 1 M NaOH at 80 °C, but still require further improvements in long-term stability for alkaline fuel cell application. An investigation of alkaline stability of model compounds demonstrated the instability of TAM cations under alkaline conditions could contribute to the deprotonation of benzylic methylene, C4 and C5 position on the triazolium ring. These results suggests that the alkaline stability of 1,2,3-triazolium cation could be improved by the introduction of substituents at the C4, C5 positions and benzylic methylene, and also provide insight and directions for organic cation designs for AEM application by the facile synthetic strategy of "click chemistry".

Long-term stability improvement of light-emitting diode using highly transparent graphene oxide paste.

A highly transparent paste adhesive is successfully fabricated by introducing graphene oxide (GO) to silicone paste adhesive by using a solvent-exchange method. The GO incorporated in the paste adhesive has a significant role in improving thermal conductivity, transparency and adhesive strength. The GO-embedded silicone paste is applied as a die-attach paste to light-emitting diodes (LEDs) in order to enhance the optical quality of the LEDs. The presence of GO in the die-attach layer of the LEDs gives rise to the enhancement of luminous intensity, effective heat dissipation, improvement of moisture barrier property as well as high adhesive strength. Consequently, the LEDs with the GO-embedded die-attach paste exhibit enhanced long-term stability. This novel approach provides a feasible and effective strategy for improving LED performance.

Toward a durable superhydrophobic aluminum surface by etching and ZnO nanoparticle deposition

Fabrication of suitable roughness is a fundamental step for acquiring superhydrophobic surfaces. For this purpose, a deposition of ZnO nanoparticles on Al surface was carried out by simple immersion and ultrasound approaches. Then, surface energy reduction was performed using stearic acid (STA) ethanol solution for both methods. The results demonstrated that ultrasound would lead to more stable superhydrophobic Al surfaces (STA–ZnO–Al–U) in comparison with simple immersion method (STA–ZnO–Al–I). Besides, etching in HCl solution in another sample was carried out before ZnO deposition for acquiring more mechanically stable superhydrophobic surface. The potentiodynamic measurements demonstrate that etching in HCl solution under ultrasound leads to superhydrophobic surface (STA–ZnO–Al(E)–U). This sample shows remarkable decrease in corrosion current density (icorr) and long-term stability improvement versus immersion in NaCl solution (3.5%) in comparison with the sample prepared without etching (STA–ZnO–Al–U).Scanning electron micrograph (SEM) and energy-dispersive X-ray spectroscopy (EDX) confirmed a more condense and further particle deposition on Al substrate when ultrasound was applied in the system. The crystallite evaluation of deposited ZnO nanoparticles was carried out using X-ray diffractometer (XRD). Finally, for STA grafting verification on Al surface, Fourier transform infrared in conjunction with attenuated total reflection (FTIR–ATR) was used as a proper technique.

基于反馈控制环路提高光电振荡器长期稳定性的方法

基于反馈控制环路提高光电振荡器长期稳定性的方法

Physical attachment of NLO chromophores to polymers for great improvement of long-term stability

Dual D-Pi-A nunchaku-like structure chromophore was designed and synthesized to improve electro-optic (EO) materials׳ EO coefficients (r33) and long term stability by a simple doping system. The r33 values of poled APC/10% DIMER1 and APC/20% DIMER1 are 23pm/V and 45pm/V respectively. After annealed at 85°C for 500h, the poled film of APC/20% DIMER1 can retain more than 85% of its initial r33 value. All these characters showed us superior prospects of application in EO devices. Chromophore DIMER1 also showed us good thermal stability; its decomposition temperature (Td) was higher than 280°C, which is enough for its application in the EO devices. Also chromophore DIMER1 had good solubility in amorphous polycarbonate (APC); it could be dissolved in APC at high loading density (25%).

Long-term stabilization of organic solar cells using hindered phenols as additives.

We report on the improvement of long-term stability of organic solar cells (OPV) using hindered phenol based antioxidants as stabilizing additives. A set of seven commercially available hindered phenols are investigated for use in bulk-heterojunction OPV. Polymer:fullerene films based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are characterized with respect to the initial power conversion efficiency and the long-term stability improvement under illumination in ambient conditions. FTIR spectroscopy is used to trace chemical degradation over time. OPV performance is recorded under ISOS-3 conditions, and an improved long-term performance of OPV devices, manifested in increased accumulated power generation (APG), is found for octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Using this additive, APG is increased by a factor of 3 compared to the reference. Observed differences in the stabilization of tested additives are discussed in terms of energetic trap states formation within the HOMO/LUMO gap of the photoactive material, morphological changes, and chemical structure.

PdxCu100−xnetworks: an active and durable electrocatalyst for ethanol oxidation in alkaline medium

Rational control of the composition and the nanostructure of catalysts can significantly affect their catalytic efficiency. Here, we demonstrated a one-pot, room temperature and aqueous synthesis of submicrometer-sized PdCu networks as superior catalysts for ethanol oxidation reaction (EOR) in alkaline medium. When correlating the activity of PdCu network catalysts for EOR with Cu content, the PdCu network catalysts show a composition-dependent ‘volcano’ behavior. The ‘volcano’ behavior is rationalized with the Sabatier principle where the reaction rate passes through a maximum when metals adsorb reaction intermediates moderately. The composition-optimized Pd73Cu27 network was intensively compared with a commercial Pd/C catalyst and it showed a superior electrocatalytic performance with a 178% enhancement in Pd-based mass activity, 160% improvement in long-term stability and better tolerance of CO-like species poisoning.

Degradation and Performance of SOFC Cathode

The scope of this paper is focused on analyzing the chemical degradation of LSCF cathode induced from many sources by GCI technique both from theoretical and experimental sides. As you know, electrochemical reaction occurring in the SOFC cathode is the reduction of oxygen, therefore cathode materials for SOFC have to posses many properties. It is necessary to evaluate the performance and degradation of SOFC cathode since improvement of long-term stability is one of the major issues during SOFC commercialization process. This research is important toward the commercialization of SOFC because efforts are being made to clarify the mechanisms of cell performance degradation and to improve durability effectively.

Brush painted V2O5 hole transport layer for efficient and air-stable polymer solar cells

As an alternative hole transport layer (HTL) to poly(3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), we investigated V2O5 thin films fabricated by simple brush painting without any post-treatments. Polymer solar cells (PSCs) with V2O5 fabricated by brush painting showed superior performance to that of conventional PEDOT:PSS based system; in particular, higher FF was obtained. Because more hydrophobic oxide surface induces better physical contact and better wetting of active blends, lower RS is obtained; thus, the resulting device shows higher performance. PSC with brush painted V2O5 at 50°C using 0.99vol% vanadium (V) oxytriisopropoxide in isopropyl alcohol exhibited the best power conversion efficiency (PCE) of 3.83%. Furthermore, employment of V2O5 as HTL leads to significant improvement in long-term stability in air (dropping of PCE of conventional PEDOT:PSS system to ~0% and retention of PCE of V2O5 based PSC to over 60% after exposure in air for 96h without any encapsulation).

Analysis of Degradation and Performance of SOFC Cathode

Electrochemical reaction occurring in the SOFC cathode is the reduction of oxygen, therefore cathode materials for SOFC have to posses many properties. It is necessary to evaluate the performance and degradation of SOFC cathode since improvement of long-term stability is one of the major issues during SOFC commercialization process. The scope of this paper is focused on analyzing the chemical degradation of LSM cathode induced from many sources by GCI technique both from theoretical and experimental sides. This research is important toward the commercialization of SOFC because it could offer valuable information to overview chemical degradations from the SOFC cathode and develop strategy to realize high-durable SOFC.