Anode Buffer Layer Research Articles

Lateral Diffusion of Holes in Anodic Buffer Layers and Its Application in Organic Light-Emitting Diodes

Lateral Diffusion of Holes in Anodic Buffer Layers and Its Application in Organic Light-Emitting Diodes

Nitride Lithium-ion Conductors with Enhanced Oxidative Stability

It is desirable to develop solid electrolytes that have both excellent reductive stability against lithium metal and oxidative stability against high-voltage cathodes. However, no inorganic superionic conductors reported thus far satisfy these criteria. Nitrides exhibit intrinsically superior stability against reduction but are often readily oxidized at voltages as low as 0.6 V. In this article, we investigated all nitride-based compounds to search for materials with improved oxidative stabilities over 2.0 V while retaining their intrinsic stability against Li metal. We found two compounds, LiPN2 and Li2CN2, with high oxidative stability > 2.0 V and low vacancy migration energies. Using fine-tuned CHGNet machine-learning interatomic potential, we found that upon introducing aliovalent dopants to introduce vacancies in Li2CN2, the dopant and vacancy strongly anchor with each other to result in trapped vacancies, which lowers ionic conductivity. In contrast, vacancies and dopants have minimal interactions in LiPN2, resulting in a high ionic conductivity. These two compounds were synthesized, but their ionic conductivities were not successfully measured because of the challenges in densification. With improved processing conditions, these compounds may serve as anode-side separators in dual-separator-type all-solid-state batteries or anode buffer layer materials interfaced with lithium metal.

Performance improvement of inverted bulk heterojunction solar cells by use of gold nanoparticles modified PEDOT: PSS as an anode buffer layer

Performance improvement of inverted bulk heterojunction solar cells by use of gold nanoparticles modified PEDOT: PSS as an anode buffer layer

A mini review on the anode buffer layers used in organic light emitting diodes

Research on organic light emitting diodes (OLEDs) are recently increasing due their unique advantages over inorganic devices. To explore upto the technology, there is a need to understand the basic device physics of OLED. The basic device physics of the device consists of basically three steps i.e. device structure, device mechanism and device characteristics & their parameters. Device structure of OLED typically consist of three basic layers but there are several intermediate layers are used to enhance device efficiency. Anode buffer layers are used to are used to reduce the interface barriers present at anode/HTL interface. Here, in in this paper different used anode buffer layers are reviewed.

Ni‐phase erosion losses at a Ni‐pore interface of microtubular solid oxide fuel cells during 5218 h of operation

AbstractA microtubular solid oxide fuel cell (μT‐SOFC) with an anode buffer layer in the inner wall of the anode is successfully fabricated. The anode buffer layer comprises nickel (Ni), gadolinium‐doped ceria, and ruthenium (Ru), of which Ru exhibits excellent stability in mixed impurity gases. At 700°C, the maximum power density of the μT‐SOFC reaches around 0.76 W/cm2 under a hydrogen flow rate of 10 sccm. After 5218 h of operation at a constant current density of 0.2 A/cm2 at 650°C, there is almost no degradation (0.093%/kh) in area‐specific resistance after 2000 h of operation under the protection of the anode buffer layer. The aggregation and migration of nanoscale Ni particles are observed at the Ni particle boundary near the triple‐phase boundary (TPB), with gradual corrosion of the Ni particles. Ni migration and loss in the TPB are determined as reasons for the decay of the fuel cells during their long‐term operation. Moreover, Ni in an amorphous state is also observed on the periphery of the Ni particles, indicating that during the corrosion process of Ni, transformation to the amorphous state occurred, which impairs the catalytic activity and electronic conductivity of Ni, resulting in a deterioration in its performance.

Ultra-fast route to fabricate large-area anode-supported solid oxide fuel cell via microwave-assisted sintering

Herein, a practical, facile, and ultra-fast technique to fabricate a large-area multi-layered solid oxide fuel cell (SOFC) is reported. In this technique, a total 25 tape-casted green films of anode-support layer, anode functional layer (AFL), electrolyte layer, and buffer layer were sequentially co-laminated and co-sintered at 1250 °C using microwave energy (2.45 GHz) in a record short time of 90 min. This process is 16 times faster than the conventional sintering process. The microwave-assisted sintering method enhanced the densification of the electrolyte and buffer layer by directly transferring the heat into the cell material. Despite the incredibly rapid processing time, the microwave-assisted sintered cell showed improved interfacial connectivity of the electrolyte and buffer layer in comparison to the conventionally sintered cell. The large-area (6 cm × 6 cm) SOFC fabricated through this route showed a maximum power density of 1.05 Wcm-2 at 750 °C. Moreover, the cell showed exceptional long-term stability tested under a constant current of 10 A for 500 h at 750 °C. The approach seems appealing in terms of its rapidity, simplicity, economic viability, and applicability in multi-layer energy devices.

Efficiency and stability improvement of non-fullerene organic solar cells with binary anode buffer layer

Efficiency and stability improvement of non-fullerene organic solar cells with binary anode buffer layer

Facile Preparation of Four-Layer MoS2 Nanosheets and Their Application to Organic Light-Emitting Diode

High-quality four-layer molybdenum disulfide (MoS2) nanosheets with lateral dimension of about 11 µm were prepared by ultrasonic treatment of MoS2 powder with assistance of 1-methyl-2-pyrrolidone (NMP) solvent. The optimal preparation conditions for the preparation of MoS2 nanosheets were investigated from the aspects of ultrasonic processing time, ultrasonic power and amount ratio of MoS2 powder and NMP solvent. At the same time, the MoS2 nanosheets were employed as anode buffer layer in organic light-emitting diode (OLED) with copper nanowire (CuNW) film being anode. MoS2 nanosheets can reduce roughness of CuNW film, protect CuNW film from oxidation and improve work function of CuNW film. Experiments show that MoS2 nanosheets can significantly improve the current density and brightness of the OLED with CuNW film being anode. The maximum brightness of the OLED with MoS2 anode buffer layer is 2.15 times that of the OLED without MoS2 anode buffer layer. The current density of the OLED with MoS2 anode buffer layer is also obviously increased compared with the OLED without MoS2 anode buffer layer.

Li3InCl6-coated LiCoO2 for high-performance all solid-state batteries

Halide solid electrolytes (HSEs) could be coated on high-voltage oxide cathodes at molecular-level via a solution process, which is highly favorable for reducing the interface impedance. However, during the preparation of composite cathodes, hydrate intermediates of HSEs are easily hydrolyzed to produce inactive impurities. In this work, the vacuum drying assisted method facilitates the generation of pure Li3InCl6 (LIC) on the surface of LiCoO2 (LCO) to improve the electrolyte/electrode solid–solid interface as well as the electrochemical stability of solid electrolyte under high voltage. By introducing Li7P3S11 as an anode buffer layer, 30 wt. %-LIC-coated LCO demonstrates high specific capacity of 121.7 mAh g−1 and good cycling stability. Our study highlights a promising method to build advanced composite cathodes for all-solid-state batteries.

Investigation of improving organic light-emitting diodes efficiency using an ultra-thin ultraviolet-ozone-treated Nb-doped ZnO film as anode buffer layer

In this study, ultraviolet (UV)-ozone treated ultrathin Nb-doped ZnO (NZO) films are developed as an efficient anode buffer layer to improve the overall performance of organic light-emitting diodes (OLEDs). The results show that the UV-ozone treated NZO buffer layer containing 1 mol% of Nb2O5 possesses a higher oxygen content and a greater work function (5.22 eV) as compared to that of an indium tin oxide (ITO) film (~4.7 eV) signifying a reduction in hole injection barrier and thus an improvement in the injection efficiency. In addition, UV-ozone treatment can increase the surface energy of NZO films while reducing their surface roughness. Importantly, the UV-ozone treated 1 nm-thick NZO film with a Nb2O5 doping concentration of 1 mol% can help to lower the turn-on voltage from 3.2 V to 2.8 V, increase the luminance from 10,450 cd/m2 to 25370 cd/m2, and improve the current efficiency from 3.46 cd/A to 5.26 cd/A, (~52 % enhancement as compared to the standard OLED device). Moreover, OLEDs with the developed buffer layer reveal a significant improvement in the roll-off phenomenon under high current densities, indicating a key role of the optimized NZO film in enhancing the carrier balance of the devices. When applied to the p-i-n structure, the NZO film also lead to a superior device performance as compared to the conventional p-i-n structure using NPB:MoO3 as a hole injection layer, suggesting a widespread use of the developed thin film. These findings therefore show a promising use of the UV-ozone treated NZO ultrathin film as an effective anode buffer material for enhancing OLED overall performance.

The Selection of Anode and Cathode Materials for Top Emission Organic Light-Emitting Diodes

In this study top emission organic light-emitting diodes (TE-OLED) were successfully fabricated on flexible PET/multilayer disordered silver nanonetwork (MDSN) substrate with conventional LiF/Al as a semitransparent cathode and Ag as a reflective anode. The effects of the hole injection layer, anode buffer layer, and an electron injection layer on the luminescence characteristics of TE-OLEDs were investigated. At first, the thickness of cathode Al is adjusted based upon the overall transmittance of the top-emission cathode and its conductivity. There is a high energy barrier for the hole between the work function of the anode Ag (4.2 eV) and the NPB highest occupied molecular orbital (HOMO) energy level (5.5 eV), which is not favorable for hole injection. This study tested four types of hole injection layer (HIL) materials. Finally, MoO3 was selected as an optimal HIL material, and the optimum thickness was adjusted, enabling the hole to be injected smoothly from the anode to the NPB and then to an emitting layer. The TE-OLED luminance reached 268 cd/m2. There is a high energy barrier between the work function of Ag and MoO3 HOMO (5.3 eV)—about 1.1 eV—which is still not conducive to the hole injection, so a thin layer of high work function metal Au (work function 5.1 eV) was added to the top of the anode silver, which more matches with the MoO3 energy level. It can make the hole easier to inject from the anode to MoO3 (HIL) and protect the silver from oxidation. At 8 V, the luminance is increased to 413.7 cd/m2, and the current efficiency is 0.81 cd/A. The luminance is significantly improved. An electron transport/hole blocking layer TPBi (10 nm) was added to enhance the electron transport capability and effectively block the holes with higher electron mobility and a higher HOMO energy level of TPBi. So that more holes can remain in the emitting layer and increase the chance of the electron-hole recombination to improve the luminance and current efficiency of TE-OLED. At 8 V, the luminance and current efficiency can reach 611.4 cd/m2 and 0.95 cd/A, respectively.

Defects Passivation Strategy for Efficient and Stable Perovskite Solar Cells

AbstractLarge area, high efficiency, and long‐term device stability are integral performance requirements for the commercialization of perovskite solar cells (PSCs). However, the high defect states density formed during the process of device preparation plays a cardinal effect in the charge recombination and ion migration process. The existence of defect states will not only seriously impair the stability but also hinder the efficiency enhancement of PSCs. A large number of studies aiming to solve this problem show that the defects can be reduced to enhance the photovoltaic performance and stability of derived PSCs by tailoring the terminal groups on the perovskite surface and modifying the surface chemical environment. Herein, a systematic and comprehensive review on the development of interfaces passivation (including the anode buffer layer, electron transport layer, the perovskite grains, and hole transport layer) for PSCs is summarized. Based on the defect passivation engineering, various feasible strategies are proposed to break the bottleneck of the commercialization process PSCs.

Low temperature synthesis of MoS2 and MoO3:MoS2 hybrid thin films via the use of an original hybrid sulfidation technique

In this study, an original hybrid technique based on rapid thermal annealing (RTA) and chemical vapor deposition (CVD) was used to synthesis MoS2 and MoO3:MoS2 hybrid thin films at low temperature on indium tin oxide (ITO). We show that using the annealing temperature, the annealing duration and the sulfur partial pressure as parameters, it is possible to switch from MoO3 (20–25 nm) to MoS2 directly without any intermediate compositions. The XPS analysis revealed a complete sulfidation at 380 °C without any deterioration of the ITO conductivity. Then, we synthesized thinner hybrid films (3nm) of MoO3:MoS2 in order to be used as anode buffer layer (ABL) in planar organic solar cells (PHJ-OPVs). We have demonstrated that the hybrid ABLs that appear best suited for use in PHJ-OPVs are those with high MoO3/MoS2 molecular ratio which have been treated around 210 °C. The introduction of the hybrid ABL with 5% of MoS2 in the PHJ-OPVs based Aluminum Phthalocyanine Chloride and Fullerene leads to a significant improvement of the OPV efficiency from 1.29% to 2.49%, this was explained by the complimentary advantages of MoO3 and MoS2.

Efficiency improvement of inverted perovskite solar cells enabled by PTAA/MoS2 double hole transporters

Hole transport layer (HTL) plays a critical role in perovskite solar cells (PSCs). We focus on the improvement of PSCs performance with MoS2 nanosheets as the anode buffer layer in the inverted photovoltaic structure. PSC with single MoS2 buffer layer shows poor performance in power conversion efficiency (PCE) and the long-term stability. By combination of MoS2 and Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) as double-layer HTL, the PCE is improved to 18.47%, while the control device with PTAA alone shows a PCE of 14.48%. The same phenomenon is also found in 2D PSCs. For double-layer HTL devices, the PCE reaches 13.19%, and the corresponding PCE of the control group using PTAA alone is 10.13%. This significant improvement is attributed to the reduced interface resistance and improved hole extraction ability as shown by the electric impedance spectroscopy and fluorescence spectroscopy. In addition, the improved device exhibits better stability because the PCE still maintains 66% of the initial value after 500 h of storage, which is higher than the 47% of the remaining PCE from device based on single PTAA or MoS2. Our results demonstrate the potential of polymer/inorganic nanomaterial as a double-layer buffer material for PSCs.

Isopropanol solvent-treated MoS2 nanosheets from liquid phase exfoliation and their applications to solution-processed anode buffer layer of organic light-emitting diode

Isopropanol solvent-treated MoS2 nanosheets from liquid phase exfoliation and their applications to solution-processed anode buffer layer of organic light-emitting diode

Improving the electrical performance of inverted perovskite solar cell with LiF anode buffer layer

Although the electrical performance of inverted PSCs is a bit lower than that of conventional PSCs at present, it has attracted increasing research attention thanks to its simple architecture for low preparation temperature and negligible hysteresis, and subsequently a high opportunity for industrial application. In general, PEDOT:PSS is employed to serve as hole transport layer (HTL) in inverted PSCs due to its high conductivity, high light transmittance, and aqueous dispersion. However, the mismatch of energy level between PEDOT:PSS and ITO is detrimental to extract the photo-induced holes, hampering further enhancement of the electrical performance of inverted PSCs. Here, a LiF anode buffer layer, whose optimization thickness is 7 nm, has been employed to modify the PEDOT:PSS HTL in inverted PSCs. Thanks to the LiF anode buffer layer, a dramatically enhancement of PCE from 16.01% of reference sample with pristine PEDOT:PSS to 18.18% of PSCs with LiF/PEDOT: PSS HTL. This enhancement is mainly ascribed to improve the charge extraction ability due to the diople effect of LiF. Therefore, this work provides a simple and effective method to increase the electrical performance of inverted PSCs. • A LiF anode buffer layer is employed to modify the PEDOT: PSS in inverted PSCs. • The PCE is a dramatically enhancement from 16.01% with pristine PEDOT:PSS to 18.18% with LiF/PEDOT:PSS. • This work provides a simple and effective method to increase the electrical performance of inverted PSCs.

Efficient planar heterojunction based on α-sexithiophene/fullerene through the use of MoO3/CuI anode buffer layer

In this work, planar heterojunction organic photovoltaic cells (PHJ-OPVs) based on alpha-sexithiophene (α-6T) and fullerene active materials were investigated. We have studied the effect of the hole transporting layer (HTL) on the performances of the PHJ-OPVs. The studied HTLs are molybdenum trioxide (MoO3), cuprous iodide CuI and MoO3 coupled with CuI (MoO3/CuI). The PHJ-OPVs were fabricated using the thermal evaporation/sublimation technique. The experimental study shows that double HTL MoO3/CuI, using 1.5 nm of CuI thickness, improves significantly the efficiency of the PHJ-OPVs compared with those with single HTLs. This enhancement is due to the fact that MoO3 contributes to the optimization of the holes collection and CuI causes significant influence on the nucleation and the growth of α-6T. CuI has led to spectacular modification of the structural properties of α-6T. When α-6T is deposited onto ITO/MoO3, the α-6T layers are amorphous, while they are crystallized into monoclinic crystalline structure with a laying down molecular orientation when they are deposited onto ITO/MoO3/CuI. The use of the double HTL and the optimization of the α-6T deposition parameters have led to an important improvement in the α-6T light absorption, roughness and the holes mobility. These findings participated in the significant enhancement of the PHJ-OPVs performances and their life time.

Water‐Induced Formation of α‐MoO3 Microcrystals as Anode Buffer Layer for Highly Efficient Polymer Solar Cells

Interfacial modification is an effective method to improve the performance of polymer solar cells (PSCs), and molybdenum oxide is one of the most widely used anode buffer layer (ABL) materials in PSCs. However, the complicated preparations with high‐temperature annealing or vacuum deposition make it uneconomic. Herein, a facile method to prepare MoOx solution in 1‐hexanol is proposed, and the component of the product can be simply adjusted by controlling the amount of introduced water. The added water facilitates the generation of α‐MoO3 microcrystals. To the best of our knowledge, this is also the first report to obtain α‐MoO3 through such a simple method. The obtained MoOx solutions are utilized to fabricate ABL in high efficiency PSCs to improve the performance. High temperature treatment is omitted, while the PCEs of binary and ternary devices can be enhanced to 16.09% and 16.81%, respectively, significantly higher than the devices with PEDOT:PSS ABL (15.55% and 15.93%). Herein, an efficient method to prepare MoOx solution in 1‐hexanol with controlled component is offered, and it is demonstrated that the MoOx ABL derived from the MoOx solution is a potential replacement to enhance the performance of high efficiency PSCs.

Using 4‐Chlorobenzoic Acid Layer Toward Stable and Low‐Cost CsPbI2Br Perovskite Solar Cells

Inorganic perovskite solar cells (PSCs) have attracted a lot of attention due to their thermal stability. Among them, CsPbI2Br are more widely studied due to their reasonable bandgap and phase stability at room temperature. However, poor moisture resistance is an urgent issue to conquer. Herein, solution‐processed 4‐chlorobenzoic acid (CBA) is used to increase the work function of a Ag electrode, enabling effective hole extraction. More importantly, CBA can effectively avoid the phase conversion of the CsPbI2Br perovskite from the cubic phase to the undesired nonperovskite δ‐phase due to the hygroscopicity of lithium bis (trifluoromethanesulphony)imide (Li‐TFSI) in 2,2,7,7‐tetrakis(N,N‐di‐pmethoxyphenylamine)‐9,9‐spirobifluorene (Spiro‐OMeTAD), enhancing the water stability of PSCs. It can also reduce the fabrication cost by replacing the expensive Au electrode and saving the evaporation energy consumption of the commonly used MoO3 anode buffer layer. Consequently, the champion device achieves a power conversion efficiency (PCE) of 14.3%, with a high open‐circuit voltage of 1.21 V. After storing in air at 20% relative humidity (RH) for 500 h, the unencapsulated device maintains more than 95% of the initial PCE.

Nanostructured Molybdenum Trioxide Layer on the Silver Anode of a Top-Incident Organic Photovoltaic Device.

A nanostructured molybdenum trioxide (MoO₃) layer was successfully fabricated utilizing various deposition rates, employed as an anodic buffer layer to separate the active layer from a silver anode and modifying the anodic surface to facilitate hole transportation for top-incident organic photovoltaic (TIOPV) devices. The deposition rate and thickness of the MoO₃ layer were crucial parameters for determining the surface morphology and work function, and the internal optical field distribution, respectively. These factors affected the performance of the devices in terms of their open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF). The baseline TIOPV device without a buffer layer had a power conversion efficiency (PCE) of only 0.47%. By contrast, with a smooth 20-nm MoO₃ buffer layer fabricated using a deposition rate of 1 Å/s (which prevented problems caused by the Ag anode), another fabricated TIOPV device had substantially higher VOC, JSC and FF values, which improved the PCE by a factor of 6.2 to 2.92%. When an additional 5-nm nanostructured MoO₃ layer was deposited at a deposition rate of 0.5 Å/s, the most efficient TIOPV device had an even greater PCE, a factor of 7.5 times higher at 3.53%.