Decrease In Series Resistance Research Articles

Improvement of Performance of CZTSSe Solar Cells by the Synergistic Effect of Back Contact Modification and Ag Doping.

To improve the performance of Cu2ZnSn(S,Se)4 solar cells, a strategy is proposed to improve the quality of absorber and back interface simultaneously by substituting V-doped Mo (Mo:V) for a conventional Mo back electrode and incorporating Ag into the Cu2ZnSn(S,Se)4 (ACZTSSe) absorber in this work. Since p+-type V-doped MoSe2 (MoSe2:V) is formed in the site between the absorber and Mo:V during selenization, the conventional Mo/n-MoSe2 back contact is modified to Mo:V/p+-MoSe2:V, a back surface passivation field (BSPF) is established at the back interface, the band bending of MoSe2:V is downward and that of bottom of the absorber is upward. Further investigation reveals that the back contact modification and Ag doping have a synergistic effect on inhibiting carrier recombination, decreasing series resistance and increasing shunt resistance, thereby leading to the PCE of device without antireflection coating increased from 8.61 to 10.98%, which is larger than the sum of increase in PCE induced by Ag doping alone (8.61 to 9.66%) and back contact modification alone (8.61 to 9.63%). It is demonstrated that the synergistic effect stems mainly from the strengthened BSPF and the further reduced back contact barrier height. The former is due to the increased difference in work function (WF) between MoSe2:V and absorber induced by the reduced WF of the absorber after Ag doping and the raised WF of MoSe2:V after V doping. The latter is due to the downshifted valence band maximum of absorber after Ag doping. This work highlights the synergistic effect of back contact modification and Ag doping on improving the performance of CZTSSe solar cells and also provides an effective way to suppress carrier recombination.

Near‐Infrared Active Tri‐nanohybrid for Enhanced Energy Harvesting

AbstractEfficient energy harvesting through full solar spectrum utilization has been considered a promising solution to world energy and environmental issues. In this direction, lead sulphide (PbS) quantum dot (QD) based hybrid materials find greater application due to their near‐infrared (NIR) active photo response. Slower charge injection and inefficient charge separation limit photoactive response of such NIR active low band gap semiconductor like PbS QDs. Moreover, constructing dual charge transfer pathways in a PbS QDs based nanocomposite through the formation of hybrids with suitable materials can be advantageous in suppressing the charge recombination. In this work, we have synthesized a nanocomposite after decorating the PbS‐QDs with semiconducting TiO2 nanoparticles modified with multiwall carbon nanotubes (MWCNT) and thus forming the tri‐hybrid (PbS‐TiO2‐MWCNT) nanocomposites. The enhanced photo‐activities of the tri‐hybrid, as compared to di‐hybrids like PbS‐TiO2, PbS‐MWCNT were confirmed by the steady state, time‐resolved photoluminescence (TRPL) measurements and reactive oxygen species (ROS) generation measurements. Higher ROS generation in the tri‐hybrid has been correlated with a faster interfacial electron transfer due to the dual charge injection pathway of PbS QD to TiO2 and MWCNT. The enhanced activity of the trio‐hybrid has also been analyzed from the first principal calculations in light of an efficient interfacial electron transfer as a result of the dual charge injection pathway. The photoelectrochemical water‐spilling response of the photoanodes in terms of photocurrent density, electrochemical impedance, and Mott–Schottky measurements on PbS‐TiO2 and PbS‐TiO2‐MWCNT photoanodes reveal that a combination of MWCNT and TiO2 exhibits an increase in electrical double layer capacitance, decrease in series resistance and enhancement of carrier density with NIR illumination at the heterojunction. Overall, all the dynamical studies at the interface of the trihybrid‐based photoanodes demonstrate its potential of utilization as a futuristic NIR‐ active photoelectrochemical water‐splitting material.

Mechanism for Improving Kesterite Solar Cells Performance via Filed Passivation Effect Induced by V‐Doped MoSe2 Interface Layer at Back Interface

One of the key issues impeding the enhancement of power conversion efficiency (PCE) of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is the severe carrier recombination at CZTSSe/MoSe2 back interface, primarily arising from the reverse electric field formed between CZTSSe and n‐type MoSe2 produced after selenization. To inhibit recombination at back interface, herein, the MoSe2 layer is converted from n‐type to p‐type by V doping in site through reaction of V‐alloyed Mo (Mo:V) back electrode with Se during selenization, and CZTSSe solar cells with p+‐type V‐doped MoSe2 (MoSe2:V) interface layer are fabricated. It is found that the PCE of the device rises from 8.34% to 9.63% as back contact changes from soda lime glass (SLG)/Mo/n‐MoSe2 to SLG/Mo:V/p+‐MoSe2:V. The quantitative analysis demonstrates that the increased PCE predominantly originated from the decreased reverse saturated current density (J0), followed by the decreased series resistance (RS), and lastly by the increased photogenerated current density (JL). The influence mechanism of the SLG/Mo:V/MoSe2:V back contact on device performance is suggested by studying the properties of Mo:V and MoSe2:V films and CZTSSe/MoSe2:V heterojunction. This work emphasizes the vital significance of the back surface passivation field induced by p+‐MoSe2:V/p‐CZTSSe heterojunction, which is enlightening for optimizing the back contact in kesterite photovoltaics.

Optimization, design and size effect on the performance of Ag/CdS:Cu/FTO/glass based Schottky diode

Influences of annealing on optical properties of spray pyrolysis deposited Cu-doped CdS (CdS:Cu) thin-films are investigated and designed Ag/CdS:Cu/FTO/glass based Schottky diode performances are discussed in detail. The sizes of the thin film are estimated through field-emission scanning electron microscopy (FESEM) images, exhibited that the films are composed of different-size, which increases with increasing the annealing temperature. The band-gap decreases from 2.79 eV to 2.75 eV with incresing annealing temperatures. According to I–V measurement, the ideality factor (η), potential height (φh) and series resistance (Rh) of Ag/CdS:Cu/FTO/glass Schottky diodes are estimated by various methods like thermionic-emission, Cheung and Norde, these all methods are consistent well. The ideality-factor and series-resistance decrease with increasing temperature and size. When the CdS:Cu thin-films are annealed at 400°C, the Ag/CdS:Cu Schottky diodes have good rectifying behaviors with an ideality-factor of 4.67–5.03, a Schottky-potential height of 0.98 eV–0.87 eV and relatively low series-resistance of 2.35kΩ-3.12kΩ. The present study will give a better understanding and insight into the Ag/CdS:Cu/FTO/glass Schottky junction.

Mechanism of improvement of efficiency of Cu2ZnSn(S,Se)4 solar cells by optimization of deposition temperature of CdS buffer layer

The physical properties of CdS buffer layers and the interface quality between CdS layer and Cu2ZnSn(S,Se)4 (CZTSSe) absorber have a significant impact on the performance of CZTSSe solar cells. In the present work, five types of CZTSSe solar cells with conventional structure (denoted as CdS-x-cells, x = 55, 60, 65, 70 and 75) were fabricated by using CdS prepared at deposition temperatures of 55, 60, 65, 70 and 75 ℃, respectively, as buffer layer, and influence mechanism of the deposition temperature of CdS layers on power conversion efficiency (PCE) of the CdS-x-cells was investigated. It is found that the PCE of the CdS-x-cells increases from 8.52% to 10.36% as the deposition temperature rises from 55 to 60 ℃ but falls from 10.36% to 7.14% from 60 to 75 ℃. The analysis on the photovoltaic and electrical parameters indicates that the increase in PCE is predominantly derived from the decreased reverse saturated current density (J0), followed by the decreased series resistance (RS) and increased shunt resistance (RSh). The decreased PCE with the further increasing deposition temperature is mainly contributed from the increased J0, followed by the decreased RSh and photogenerated current density (JL). The influence mechanism of deposition temperature of the CdS layer on PCE is suggested via quantitatively analysis of influence of electrical, optical properties and crystal quality of CdS prepared at various deposition temperatures on JL and electrical parameters of CdS-x-cells. This work is helpful for improvement of PCE of CZTSSe solar cells by modification of properties of buffer layer.

Impact of B2H6 plasma treatment on contact resistivity in silicon heterojunction solar cells

We investigated the effect of the B2H6 plasma treatment on p-type hydrogenated amorphous silicon (p-a-Si:H) surfaces for high-performance silicon heterojunction (SHJ) solar cells. Secondary ion mass spectroscopy measurements revealed that the boron concentration at the p-a-Si:H surface is increased by employing the B2H6 plasma treatment. Furthermore, specific contact resistance is decreased by about one-third after the B2H6 plasma treatment. No degradation of passivation performance is induced by the B2H6 plasma treatment. The power conversion efficiency of the SHJ solar cells with the B2H6 plasma treatment is improved by the increase in fill factor (FF) due to decreased series resistance and increased shunt resistance. From numerical simulations, the upward band bending is enhanced at the heterointerface between transparent conductive oxide (TCO) and p-a-Si:H by the B2H6 plasma treatment, which is responsible for the improved FF owing to facilitated tunneling holes from c-Si to p-a-Si:H layers and the TCO/p-a-Si:H heterointerface.

High Performing Inverted Flexible Perovskite Solar Cells via Solution Phase Deposition of Yttrium-Doped SnO2 Directly on Perovskite

Solution processing of flexible perovskite solar cells (f-PSCs) provides an avenue for scalable, high-throughput printing of lightweight, scalable, and cost-effective flexible solar cells. However, the deposition of fully solution-processed metal oxide charge transport layers on perovskites has been limited by solvent incompatibilities and high processing temperatures for metal oxide nanoparticles. In this study, we present high-performance, inverted f-PSCs from the direct deposition of yttrium-doped SnO2 nanoparticles functionalized with acetate on top of perovskite as an ink in anhydrous ethanol via blade coating. Yttrium doping improved device performance by improving the charge extraction with a decreased series resistance leading to improvements in the open-circuit voltage and fill factor. The champion power conversion efficiency for 0.1 cm2 devices increased from 14.3% for undoped SnO2 to 16.5% with 2% Y:SnO2 doping, which is unprecedented for f-PSCs on ITO-PET substrates employing SnO2 as an ETL.

High‐Efficiency Wide‐Bandgap Perovskite Solar Cells for Laser Energy Transfer Underwater

Wide‐bandgap perovskite solar cells (PSCs) are a promising technology with a series of potential applications, including tandem photovoltaics, solar‐driven electrochemical energetic devices, and outfit morphing power supply for underwater equipment. However, the energy‐level difference between the charge transport layer and perovskite may result in inefficient interfacial charge extraction, leading to the series carrier accumulation at the interface that impairs the photovoltaic performance. Herein, [6,6]‐phenyl C61 butyric acid methyl ester is introduced between SnO2 and FAPbBr3 to alleviate the energy‐level mismatch. Significant photoluminescence quenches and decreased series resistance both verify the promoted interfacial charge extraction efficiency. Besides, the film on the flattened nonwetting electronic transport layers film has better quality, thus reducing defect density and nonradiative recombination. As a result, a 20% power conversion efficiency (PCE) improvement, from 7.02% to 8.55%, is achieved under AM1.5G illumination. More importantly, for the first time, this work demonstrates a highly efficient PSC with a PCE over 43% under the 532 nm laser condition, providing a promising wireless fast charging way with high‐power laser irradiation in deep ocean.

Influence of SWCNT on the Electrical Behavior of an Environmentally Friendly CH3NH3SnI3 Perovskite-Based Optoelectronic Schottky Device

The lead-free tin-based halide perovskite CH3NH3SnI3 has recently been explored in a wide range of optoelectronic device applications. However, the charge conduction process of the CH3NH3SnI3 perovskite layer is hindered by the presence of vacancies resulting from tin oxidation, sample defects, and trap states, which limit the performance of the device. In this study, we introduced single-walled carbon nanotubes (SWCNTs) into the perovskite to enhance the charge conduction of the device. To demonstrate this, CH3NH3SnI3 perovskite and its composites with SWCNTs were synthesized and used as an active layer in a sandwich-structured device. Electrical measurements show that the device based on SWCNTs exhibits superior performance compared to the device consisting solely of perovskite. Incorporating SWCNTs into the device improves conductivity and reduces series resistance. Specifically, in the absence of light, SWCNTs increase the conductivity from 3.8 × 10–5 to 1.6 × 10–4 S/m and decrease the series resistance from 348.25 to 34.80 Ω. Under illumination, SWCNTs further increase conductivity to 4.0 × 10–4 S/m from 8.1 × 10–5 S/m and decrease series resistance to 19.20 Ω from 220.56 Ω. The results suggest that SWCNT can serve as a channel for charge extraction. An analysis of space charge limited current (SCLC) conduction indicates that incorporating SWCNT decreases the trap energy from 103.22 to 79.70 meV under dark conditions. This implies that SWCNT also acts as a filler for trap states. Based on these findings, it appears that the SWCNT-CH3NH3SnI3 perovskite composite has the potential to yield high-performance optoelectronic devices. This study presents an intriguing approach for enhancing carrier transfer with minimal recombination loss and could serve as a source of inspiration for future research in the optoelectronics field.

Composition and electronic structure of {rm SiO}_{rm x}/{rm TiO}_{rm y}/Al passivating carrier selective contacts on n-type silicon solar cells

Carrier-selective and passivating SiO_{rm x}/TiO_{rm y} heterocontacts are an attractive alternative to conventional contacts due to their high efficiency potentials combined with relatively simple processing schemes. It is widely accepted that post deposition annealing is necessary to obtain high photovoltaic efficiencies, especially for full area aluminum metallized contacts. Despite some previous high-level electron microscopy studies, the picture of atomic-scale processes underlying this improvement seems to be incomplete. In this work, we apply nanoscale electron microscopy techniques to macroscopically well-characterized solar cells with SiO_{rm x}/TiO_{rm y}/Al rear contacts on n-type silicon. Macroscopically, annealed solar cells show a tremendous decrease of series resistance and improved interface passivation. Analyzing the microscopic composition and electronic structure of the contacts, we find that partial intermixing of the SiO_{rm x} and TiO_{rm y} layers occurs due to annealing, leading to an apparent thickness reduction of the passivating SiO_{rm x}. However, the electronic structure of the layers remains clearly distinct. Hence, we conclude that the key to obtain highly efficient SiO_{rm x}/TiO_{rm y}/Al contacts is to tailor the processing such that the excellent chemical interface passivation of a SiO_{rm x} layer is achieved for a layer thin enough to allow efficient tunneling through the layer. Furthermore, we discuss the impact of aluminum metallization on the above mentioned processes.

The Effects of Pt-Doped TiO2 Nanoparticles and Thickness of Semiconducting Layers at Photoanode in the Improved Performance of Dye-Sensitized Solar Cells.

This work synthesized Pt-doped dye-sensitized solar cells (DSSC) with different molar ratios and thicknesses. The materials were revealed fully through X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photovoltaic properties of the sample were studied by UV-visible spectroscopy, electrochemical impedance spectroscopy (EIS), and IPEC (incident photon-to-current conversion efficiency) techniques. EIS analysis established the decrease in series resistance at the electrolyte interface. It could be one of the reasons for the increase in electron transfer rate and decrease in the recombination process at the interface. Statistical data obtained from optical and electrical investigations revealed that the electrical power-output efficiency of DSSC was 14.25%. It was found that a high ratio of Pt doping and thinner thickness can promote cell performance, owing to the reduction of series resistance, lower bandgap, and high dye adsorption. Doping TiO2 with Pt reduced its energy bandgap and introduces intermediate energy levels inside TiO2 to facilitate the transition of electrons at low excitation energies. The absorbance of the samples 0.15 M Pt and 0.25 M Pt showed improvement in the wavelength ranging from 200 to 800 nm by Pt doping.

UV Ozone based rapid low temperature fabrication of flexible dye sensitized solar cells

Herein, we have developed a multilayer TiO2 film thickness of around 4 µm at lower temperature (120 °C) by spin coating and doctor blade technique on polyethylene terephthalate (ITO-PET) substrate. Further, the additional processing step Ultravoilet-Ozone (UVO3) treatment was performed on TiO2 electron transport layer (ETL) to enhance the performance of FDSSCs. UVO3 treatment significantly improved the crystallinity and charge transport characteristic of ETL by removing the organic impurities. The photovoltaic devices based on 4 h of UVO3 treated TiO2 film exhibited superior device performance with an overall power conversion efficiency (PCE) of 2.53% compared to 1.43% (without UVO3 treatment). Electrochemical impedance measurement indicated that TiO2 layer treated with UVO3 decreased series resistance, electron recombination and improved electron life substantially. The improved device properties, simple preparation procedure and low processing cost, enable this FDSSCs fabrication method to be a credible alternative of conventional techniques.

Role of zinc tin oxide passivation layer at back electrode interface in improving efficiency of Cu2ZnSn(S,Se)4 solar cells

We report a Cu2ZnSn(S,Se)4 (CZTSSe) solar cell with a modified structure via inserting an intermediate zinc tin oxide (ZTO) layer between Mo electrode and CZTSSe layer in the conventional CZTSSe solar cell. Comparing with the conventional CZTSSe solar cells (without ZTO layer), the best photovoltaic performance is obtained for the solar cells with a modified structure. When an 8-nm-thick ZTO passivation layer is inserted, the corresponding device shows the improvements in performance parameters, including short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF). As a result, we obtained a maximum power conversion efficiency (PCE) of 8.95% for the optimized device with an 8-nm-thick ZTO layer, which is ascribed to the increase of shunt resistance (RSh), decrease of series resistance (RS) and decrease of reverse saturation current density (J0). Our results suggest that the ZTO is a promising passivation material at back electrode interface for optimizing the performance and improving efficiency of CZTSSe-based solar cells.

A Universal and Facile Method of Tailoring the Thickness of Mo(Sx,Se1−x)2, Contributing to Highly Efficient Flexible Cu2ZnSn(S,Se)4 Solar Cells

Flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have attracted considerable attention due to their potential application in specific areas such as power sources for wearable electronics. However, the over‐thick Mo(Sx,Se1−x)2 at the back contact is one of the factors that limit the device performance. Herein, a facile strategy to inhibit the thick Mo(Sx,Se1−x)2 layer by adding a proper proportion of sulfur during selenization is reported. It is found that the thickness of Mo(Sx,Se1−x)2 can be effectively tailored via tuning the proportion of S, enabling a substantial decrease in series resistance. The suppression mechanism is mainly ascribed to the change of orientation of Mo(Sx,Se1−x)2 induced by S, which limits the diffusion of Se to Mo. Accordingly, the total area efficiency of the flexible CZTSSe device improves significantly from 5.5 to 8.9% with the addition of 2% S, followed by a drop with more S. Furthermore, it is demonstrated that this strategy can also be applied to both kesterite and chalcogenide absorbers deposited on rigid Mo substrates to suppress the thick Mo(Sx,Se1−x)2 layer, indicating the universality of this method. Overall, this work provides a general, facile, and effective approach to modify the back contact interface without introducing extra blocking layers.

Accurate determination of junction temperature in a GaN-based blue light-emitting diode using nonlinear voltage-temperature relation

We investigate the junction temperature measurements for GaN-based blue light emitting diodes (LEDs) using nonlinear dependence of the forward voltage (Vf) on temperature. Unlike the conventional linear model of the dependence of Vf on temperature, the modeling of the temperature dependent Vf with a quadratic function showed good agreements with measured data in the temperature range between 20 and 100 °C. Using the proposed quadratic model, the junction temperature and thermal resistance of the measured LED could be accurately determined as the ambient temperature varied. It was observed that the junction temperature increment remained almost unchanged as the ambient temperature increased from 20 to 80 °C, which could be attributed to the interplay between the decrease in series resistance and the increase in non-radiative recombination with increasing temperature. The presented method for accurate determination of the junction temperature is expected to be advantageously employed for the thermal management of high-power LEDs.

Effects of the photoactive layer properties and current transmission mechanism on optical and electrical characteristics of organic photovoltaic

The P3HT:PCBM is an important organic material as an active layer for bulk heterojunction (BHJ) organic photovoltaics (OPVs). However, in terms of photophysical properties, blend ratios of both materials and device design is an important parameter for OPVs devices. In this study, the P3HT:PCBM photoactive layer, blended in different proportions by mass (1:1, 1:0.8, 1:0.6) was coated on the PEDOT:PSS surface using the spin coater method for different devices. Finally, Al have been evaporated on the photoactive layer and the device structure completed. In other examples, 2 nm lithium fluoride (LiF) as buffer layer evaporated on the active layer for each blending ratio before metal. Optical absorption, AFM, XRD, Raman and XPS measurements were taken for each active layer and it was observed that the surface morphology and absorption characteristic of the active layer changed according to the mixing ratios. This change in active layer properties directly affected the device parameters. Electrical characterization of the six different devices performed with current density-voltage (J–V) measurement and by used a solar simulator under 100 mW/cm2 irradiation intensity. Depending on the increase in short circuit current density (Jsc) and open current voltage (Voc) values in the devices, the power conversion efficiency (PCE) of the OPVs obtained varied between 0.86% and 2.74%. This change can be attributed to the fact that the P3HT:PCBM photoactive layer forms a smoother surface morphology depending on the PCBM ratio and the series resistance decreases. Another reason for this change in PCE can be explained by the effective electron injection of the LiF layer, LiF/Al layer with lower work function and less carrier deposition at its metal-active layer interfaces. It result has been obtained that the active layer with a ratio of 1:0.8 has a more homogeneous surface morphology and the series resistance decreases, the presence of the LiF layer in the device structures increases the Jsc and Voc, accordingly the PCE increases to 2.74%. These results showed that BHJ OPV with high PCE can be obtained with the ideal mixing ratio and appropriate device design.

Analysis of degradation mechanisms in GaN-based light-emitting diodes under reverse-bias stress: effects of defects and junction-temperature increase

Degradation phenomena of GaN-based blue LEDs are investigated from comprehensive electrical, optical, and thermal analyses. After constant reverse-bias stress, the LED sample under investigation shows permanent degradations indicated by increases both in the tunneling/sidewall leakage current in the low-current region and the nonradiative current in the high-current region. A subsequent decrease in series resistance and increase in junction temperature are also observed. The degradation at high currents is analyzed in terms of the radiative recombination current utilizing the information of the internal quantum efficiency (IQE), which has been rarely attempted. All of the observed degradations can be attributed to the increase in defect density in the active layer of the LED chip under reverse-bias stress. This work emphasizes that many important reliability-related features of LEDs are functions of defects and the junction temperature and that the IQE can provide crucial information in the analysis. The increased junction temperature would have further detrimental effects on the device performance and eventually lead to device failure. The analyses presented in this work shed more light on understanding the degradation phenomena in the GaN-based LEDs under reverse-bias stress.

Efficiency increase in multijunction monochromatic photovoltaic devices due to luminescent coupling

We present a multijunction detailed-balance model that includes the effects of luminescent coupling, light trapping, and nonradiative recombination, suitable for the treatment of multijunction solar cells and photonic power converters—photovoltaic devices designed to convert the narrow-band light. The model includes both specular and Lambertian reflections using a ray-optic formalism and treats nonradiative processes using an internal radiative efficiency. Using this model, we calculate and optimize the efficiency of multijunction photonic power converters for a range of material qualities and light-trapping schemes. Multijunction devices allow increased voltage with lower current, decreasing series resistance losses. We show that efficiency increases significantly with an increased number of junctions, even without series resistance, when the device has an absorbing substrate. Such an increase does not occur when the device has a back reflector. We explain this effect using a simplified model, which illustrates the origin of the decreased radiative losses in multijunction devices on substrates.

Analysis of performance degradation during steady-state and load-thermal cycles of proton exchange membrane water electrolysis cells

A membrane-electrode assembly based on a 90 μm short-side-chain Aquivion® proton exchange membrane and containing low catalyst loadings, 0.4 mg IrRuOx cm−2 and 0.1 mg Pt cm−2 at anode and cathode, respectively, is investigated for combined thermal and load cycling at high current density (3 A cm−2) in water electrolysis cell. Durability tests under steady-state and load-thermal cycles are compared to evaluate the efficiency losses under specific operating conditions. Ac-impedance spectra and post-operation analyses are carried out to investigate the degradation mechanism. Catalyst degradation occurs more rapidly under cycled operation whereas mass transfer issues are relevant especially under steady-state mode. Membrane thinning appears to be affected by the uptime hours at high current density. The overall cell voltage increase is slightly larger for the cycled operation compared to the steady-state mode. However, this is essentially related to a compensation effect associated to a larger decrease of series resistance during the steady-state durability test. The dynamic electrolysis mode at high current density does not exacerbate significantly the degradation issues of low catalyst loading MEAs compared to a steady-state operation. This confirms the proper dynamic characteristics of the polymer electrolyte membrane electrolyser.

Efficient Cathode Interfacial Materials Based on Triazine/Phosphine Oxide for Conventional and Inverted Organic Solar Cells

Cathode interfacial layers (CIL) have been applied in organic solar cells (OSCs) for the enhancement of photovoltaic characteristics. Most of them are employed in either conventional organic solar cells (COSCs) or inverted organic solar cells (IOSCs) only. Herein, we have designed and synthesized two cathode interfacial materials, namely, 3-(4,6-bis(4-bromophenoxy)-1,3,5-triazin-2-yl)-2,6-difluorophenyl)diphenylphosphine oxide (Br-PO-TAZ) and 4,4′-((6-(3-(diphenylphosphoryl)-2,4-difluorophenyl)-1,3,5-triazine-2,4-diyl)bis(oxy))dibenzonitrile (CN-PO-TAZ), and utilized them as CILs for both COSCs and IOSCs. The incorporation of our new CIL layers significantly enhanced the photovoltaic performance compared to COSCs and IOSCs without the CILs. The CN-PO-TAZ exhibited a power conversion efficiency (PCE) of 8.19% for COSCs and 8.33% for IOSCs, whereas Br-PO-TAZ yielded a PCE of 8.15% for COSCs and 8.23% for IOSCs, respectively. The improved performance was attributed to the multiple favorable factors: significantly reducing leakage current, decreasing series resistance, suppressing recombination, efficient charge transport and collection. Moreover, the CIL layers helped for sustaining device stability because they served as an internal shield against humidity.