Hole Blocking Layer Research Articles

Photovoltaic performance of boron doped silicon nanoparticles/textured silicon/organic polymer solar cells with APTES modification and hole blocking layer

Photovoltaic performance of boron doped silicon nanoparticles/textured silicon/organic polymer solar cells with APTES modification and hole blocking layer

The Influence of Helium Dielectric Barrier Discharge Jet (DBDjet) Plasma Treatment on Bathocuproine (BCP) in p-i-n-Structure Perovskite Solar Cells.

A bathocuproine (BCP) layer is typically used as the hole-blocking layer in p-i-n-structure perovskite solar cells (PSCs) between PC61BM and Ag electrodes. Before evaporating the Ag, we used a low-temperature (<40 °C) atmospheric-pressure dielectric barrier discharge jet (DBDjet) to treat the BCP with different scan rates. The main purpose of this was to change the contact resistance between the BCP layer and the Ag electrodes through surface modification using a DBDjet. The best power conversion efficiency (PCE) of 13.11% was achieved at a DBDjet scan rate of 2 cm/s. The He DBDjet treatment introduced nitrogen to form C−N bonds and create pits on the BCP layer. This deteriorated the interface between the BCP and the follow-up deposited-Ag top electrode. Compared to the device without the plasma treatment on the BCP layer, the He DBDjet treatment on the BCP layer reduced photocurrent hysteresis but deteriorated the fill factor and the efficiency of the PSCs.

Recombination Dynamics in PbS Nanocrystal Quantum Dot Solar Cells Studied through Drift–Diffusion Simulations

The significant performance increase in nanocrystal (NC)-based solar cells over the last decade is very encouraging. However, many of these gains have been achieved by trial-and-error optimization, and a systematic understanding of what limits the device performance is lacking. In parallel, experimental and computational techniques provide increasing insights into the electronic properties of individual NCs and their assemblies in thin films. Here, we utilize these insights to parameterize drift–diffusion simulations of PbS NC solar cells, which enable us to track the distribution of charge carriers in the device and quantify recombination dynamics, which limit the device performance. We simulate both Schottky- and heterojunction-type devices and, through temperature-dependent measurements in the light and dark, experimentally validate the appropriateness of the parameterization. The results reveal that Schottky-type devices are limited by surface recombination between the PbS and aluminum contact, while heterojunction devices are currently limited by NC dopants and electronic defects in the PbS layer. The simulations highlight a number of opportunities for further performance enhancement, including the reduction of dopants in the nanocrystal active layer, the control over doping and electronic structure in electron- and hole-blocking layers (e.g., ZnO), and the optimization of the interfaces to improve the band alignment and reduce surface recombination. For example, reduction in the percentage of p-type NCs from the current 1–0.01% in the heterojunction device can lead to a 25% percent increase in the power conversion efficiency.

Top‐Illuminated Organic Photodetectors beyond 1000 nm Wavelength Response Enabled by a Well‐Defined Interfacial Engineering

AbstractNear infrared (NIR) and shortwave infrared (SWIR) image technologies are of interest for many emerging applications. Among photodetector technologies, organic photodetectors (OPDs) are groundbreaking light sensors with unique photon‐to‐electron responses at various wavelengths that offer limitless flexibility in field applications due to the tunable design of organic semiconductors. Herein, a top‐illuminated OPD deposited on bottom aluminum electrode with a spectral response beyond a wavelength of 1000 nm is reported, which suggests a feasibility for image sensors integrated with bottom readout circuit. The results reveal that a device composed of aluminum‐doped zinc oxide, nickel oxide, and indium‐doped zinc oxide as hole blocking layer, hole transporting layer, and transparent top electrode, respectively, shows the best performance at a wavelength of ≈1000 nm, achieving an outstanding external quantum efficiency of 74% with a responsivity of 0.64 A W−1 and a detectivity of 6.6 × 1012 Jones. The device also performs a fast photocurrent response time of 9.8 µs and a linear dynamic range of 98 dB. To the best of knowledge, this device performance is one of the best reported to date for NIR and SWIR OPDs. The values are also comparable to commercially available inorganic photodetectors.

Inkjet-Printed Tin Oxide Hole-Blocking Layers for Organic Photodiodes

We investigated the fabrication of inkjet-printed SnO2 hole-blocking layers (HBLs) for organic photodiodes (OPDs). HBLs printed at different drop spacings were fabricated, and the effect of printing parameters on the layer quality was analyzed. These layers were incorporated into polymer:nonfullerene bulk-heterojunction OPDs, and their influence on the rectification, spectral responsivity, specific detectivity, and detection speed of the device was investigated. The OPDs fabricated with a drop spacing of 35 μm corresponding to a thickness of 31 ± 7 nm exhibited the best overall performance. These OPDs reached state-of-the-art performance with spectral responsivities of >0.5 A W–1, low dark current densities in the order of 5 nA cm–2, bandwidths of >2 MHz, and peak specific detectivities of ∼1011 Jones at 740 nm.

Enhancing the Luminous Efficiency of Ultraviolet Light Emitting Diodes By Adjusting the Al Composition of Pre-Well Superlattice

The lower luminous efficiency is a critical issue for ultraviolet light-emitting diodes (UV-LEDs) owing to the poor carrier injection efficiency and high dislocation density. Here, we can improve the luminous efficiency in two avenues by adjusting the Al composition of the InGaN/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> N pre-well superlattice. First, due to the strain-induced piezoelectric and intrinsic spontaneous polarization, a large number of electrons gather at the InGaN/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> N interface, which improves the electron concentration of the pre-well superlattice and lowers the conduction band energy of the first quantum barrier layer (FQB), thus enhancing the electron injection efficiency. Second, the pre-well superlattice can act as a hole blocking layer to prevent holes from leaking into the n-type layer and confine them in the quantum well layer. As the Al composition increases, the hole blocking effect of the pre-well superlattice is strengthened. However, higher Al composition decreases the lattice quality, which makes it possible for carrier loss through defect-related non-radiative recombination. Finally, the output power of the samples with 5% Al composition in the pre-well superlattice is 5.9% and 102.5% higher than that of the samples with 3% and 7% Al composition, respectively.

Modeling Dark Current Conduction Mechanisms and Mitigation Techniques in Vertically Stacked Amorphous Selenium-Based Photodetectors.

Amorphous selenium (a-Se) with its single-carrier and non-Markovian, hole impact ionization process can revolutionize low-light detection and emerge to be a solid-state replacement to the vacuum photomultiplier tube (PMT). Although a-Se-based solid-state avalanche detectors can ideally provide gains comparable to PMTs, their development has been severely limited by the irreversible breakdown of inefficient hole blocking layers (HBLs). Thus, understanding of the transport characteristics and ways to control electrical hot spots and, thereby, the breakdown voltage is key to improving the performance of avalanche a-Se devices. Simulations using Atlas, SILVACO, were employed to identify relevant conduction mechanisms in a-Se-based detectors: space-charge-limited current, bulk thermal generation, Schottky emission, Poole-Frenkel activated mobility, and hopping conduction. Simulation parameters were obtained from experimental data and first-principle calculations. The theoretical models were validated by comparing them with experimental steady-state dark current densities in avalanche and nonavalanche a-Se detectors. To maintain bulk thermal generation-limited dark current levels in a-Se detectors, a high-permittivity noninsulating material is required to substantially decrease the electric field at the electrode/hole blocking layer interface, thus preventing injection from the high-voltage electrode. This, in turn, prevents Joule heating from crystallizing the a-Se layer, consequently avoiding early dielectric breakdown of the device.

Modeling and Analysis of High-Performance Triple Hole Block Layer Organic LED Based Light Sensor for Detection of Ovarian Cancer

In this paper a novel triple hole block layer (HBL) structure of the OLED is proposed that depicts an enhanced luminescence of 25285 cd/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with an improvement of 47% over multilayered OLED architecture. It also owes 74% improvement in luminous power efficiency. An in-depth numerical analysis based on Poisson and drift diffusion equation is undertaken and validated against the internal device analysis. The analysis results highlight an enhanced recombination rate within the proposed device. High electron injection and efficient hole blocking contributes to improved recombination rate. Triple HBL OLED is therefore used for diagnosis of ovarian cancer. The device illustrated good response towards varying wavelengths generating a maximum photo current value of 93 mA. A healthy person can be differentiated from an oncological cancer patient based on fluorescence produced by their urine. The fluorescence values for healthy person and oncological cancer patient are in the range of 420 and 440 nm, correspondingly. The cathode current produced by OLED corresponding to these two wavelengths are 5 and 1 mA respectively. Hence, the proposed device can successfully diagnose the ovarian cancer patient. Further, the methodology proposed for diagnosis of ovarian cancer can help in developing a portable, flexible low cost biomedical sensor.

High-Performance Pentacene/ZnO UV-Visible Photodetector Using Solution Method

This work reports a Pd/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /ZnO/pentacene/ PEDOT:PSS/indium-doped tin oxide (ITO) structure-based high-performance ultraviolet (UV)-visible photodetector fabricated on an ITO substrate. The poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) acts as the hole transport layer (HTL), while aluminum oxide (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) acts as a hole blocking layer (HBL) to reduce the dark current. At -1 V bias voltage, the proposed device shows the responsivity, sensitivity, detectivity, and external quantum efficiency (EQE) of 25.51 A/W, 2574.19, 1.52 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> Jones, and 10171% at 311 nm (UV region) while the corresponding values at 565 nm (visible region) are found to be 0.36 A/W, 346.66, 2.17 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> Jones, and 79.65%, respectively.

Highly Stable Interdigitated PbS Quantum Dot and ZnO Nanowire Solar Cells with an Automatically Embedded Electron-Blocking Layer

We have constructed heterojunction iodide ligand PbS quantum dot (QD) and ZnO nanowire (NW) solar cells. In these interdigitated structures, PbS QDs are well-embedded within ZnO NWs grown on a dense ZnO layer. A Au back contact is directly formed on the iodide ligand PbS QD surface layer. In the widely studied colloidal QD-based heterojunction solar cells, the PbS QD active layer is sandwiched between the hole-blocking layer (or electron-accepting layer) and the electron-blocking layer (EBL) (or hole-transport layer). In contrast, our solar cells contain no EBL except an additional thin PbS QD capping layer, which was deposited on the interdigitated layer to ensure the complete infiltration of the PbS QDs, and prevent shortening between the ZnO NWs and Au back contact. The interdigitated layer was constructed using a layer-by-layer dip-coating method to achieve sufficient infiltration of PbS QDs in the ZnO NWs. Owing to highly efficient charge separation in the interdigitated structure, our cell achieved a high external quantum efficiency in the visible and infrared regions, despite using only iodide ligand PbS QDs. Using cross-sectional Kelvin probe force microscopy, we confirmed that the PbS QD capping layer formed between the ZnO NW and Au back contact intrinsically functioned as an EBL. Consequently, the solar cells with ZnO NWs and iodide ligand PbS QDs maintained their performance after 500 days of storage in air without encapsulation. This stability performance surpasses most of the previously reported solar cells with PbS QDs. An encapsulated 1.0 cm2 solar cell maintained its power output for over 75 h under continuous one-sun illumination with no significant degradation. The proposed solar cell architecture with an automatically embedded EBL can realize highly efficient and stable colloidal QD-based solar cells. Moreover, the interdigitated architecture concept can be extended to various organic and inorganic hybrid solar cells.

(Invited) Colloidal Quantum Dots for Enhancing Performance of Avalanche Amorphous-Selenium Photodetectors

Photodiodes using amorphous-selenium (a-Se) have gained significant attention in medical diagnostic imaging due to their avalanche phenomena. At high electric fields above 70 V/μm, holes in a-Se undergo impact ionization which increases the effective sensitivity of the photodetector. However, at the high electric fields required for avalanche gain, dark current due to charge injection from metallic electrodes can become a significant source of noise, limiting the dynamic range of the device. To maximize gain while maintaining low dark conductivity, and to achieve reliable and repeatable impact ionization without irreversible breakdown, we need a non-insulating n-type hole-blocking/electron-transporting layer with a high dielectric constant. Among previously reported hole blocking layers that include both polymers and crystalline inorganic materials, vacuum deposited bulk cerium dioxide (CeO2) has shown promising results and has been successfully utilized in n-i-p avalanche a-Se sensors. However, bulk CeO2 cannot be directly deposited on a-Se owing to the low crystallization temperature of a-Se. In this talk, I will present our results on colloidal CeO2 quantum dots as potential hole blocking layers for a-Se devices. These CeO2 quantum dots are electronically passivated by surfactants/ligands and spin coated directly on a-Se at room temperature without inducing crystallization. Owing to quantum confinement, the QDs have a larger bandgap than bulk CeO2 thus raising the effective hole energy barrier. Prototype devices based on these QDs as interface layers on a-Se achieved an ultra-low dark current of 30 pA/cm2 at 70 V/μm which is three orders of magnitude lower than any avalanche a-Se device previously reported and may be the lowest dark current ever recorded for an avalanche device operated at room temperature.

Solution processable transition metal oxide ultra-thin films as alternative electron transport and hole blocking layers in dye sensitized solar cells

An electron transporting and hole-blocking layer (ETL) between the fluorine-doped tin oxide (FTO) and mesoporous titanium dioxide interface of photoanode is essential in dye-sensitized solar cells (DSCs) for improving their photovoltaic performance. In the present work, we have examined the potential for further improving device performance by using alternative materials for ETLs. Accordingly, the effect of replacing TiO2 based ETLs with spin coated ultra-thin transition metal oxides (TMOs), molybdenum trioxide (MoO3) and tungsten trioxide (WO3) films has been studied. TMO films of 10 nm thickness have been found to be optimal for obtaining good transparency and charge transport properties, without compromising device performance. Further, devices fabricated with surfactant assisted (SA-) MoO3 ETLs have shown efficiency ∼4%, which is comparable with devices based on conventionally prepared TiO2 ETLs. In addition, a significant improvement in efficiency (15 %) has been observed for DSCs prepared using SA-WO3 films. The overall improvement in device efficiency is attributed to the increase in short-circuit current density without loss of open circuit potential and fill factor. Detailed analyses of results suggest that in addition to surface morphology, transparency and charge transport properties; oxygen vacancies in sub-stoichiometric TMOs also plays an important role in determining the device performance. The findings reveal that TMOs have significant potential to replace TiO2 ETL in DSCs and other third generation solar cell, viz. perovskite and polymer solar cells.

Effect of 1,8-Diiodooctane Content on the Performance of P3HT:PC61BM Bulk Heterojunction Photodetectors

A series of polymer photodetectors with device configuration of ITO/PEDOT:PSS/P3HT:PC61BM/C60/Al were prepared by using P3HT as the donor material and PC61BM as the acceptor material. By regulating the content of 1,8-diiodooctane (DIO) (V/V: 1%, 3%, 5%) as a processing additive, the morphology of the active layer can be greatly improved. With C60 as the hole blocking layer, the dark current density of the device can be reduced by about an order of magnitude. When employing 3% DIO (V/V) in the active layer processing, the photodetetcors present the best performance, and the detectivity of the device is 1.52×1012 Jones at 540 nm under a bias of −0.1 V. Moreover, it also has a wider linear dynamic range of 60 dB as well as faster response speed (τr/τf=0.53/0.71 µs) than those of devices with other content of DIO additives.

Effect of lanthanum tungstate hole-blocking layer for improvement of energy efficiency in anode-supported protonic ceramic fuel cells

Effect of lanthanum tungstate hole-blocking layer for improvement of energy efficiency in anode-supported protonic ceramic fuel cells

MgO blocking layer induced highly UV responsive TiO2 nanoparticles based self-powered photodetectors

• MgO nanofilm was proposed to serve as hole blocking layer between TiO 2 and FTO. • The wide band gap of MgO provides a favorable tunnel for electrons. • The UV PD presents high responsivity and fast response speed. Self-powered ultraviolet (UV) photodetector (PD) with high responsive performances are highly required. However, most reported work are focused on modifying the interface between semiconductor and electrolyte to improve separation of electrons and hole, but little work has been devoted to the interface between semiconductor and the conductive substrate, where recombinations of electrons and holes occurred, resulting in much photocurrent loss. Therefore, in this work, MgO ultra-thin layer was proposed to serve as a hole blocking layer (HBL) between TiO 2 nanoparticles (NPs) layer and the FTO conductive substrate. SEM, EDX and XRD characteristics demonstrate the successful attachment of MgO nanofilm on FTO substrate. By controlling TiCl 4 hydrolysis process, two layers of TiO 2 NPs including the bottom compact layer and the upper multiple branches layer have grown on MgO nanofilm modified FTO substrate. The self-powered UV PDs are assembled by sandwiching TiO 2 NPs with or without MgO between two FTO substrates. The MgO/TiO 2 NPs based UV PD exhibits appealing performance with responsivity of 29.97 AW −1 , sensitivity of 10 4 and rising time of 0.02 s, showing 2, 5 and 2 times higher than those of the pure-TiO 2 NPs based UV PD, respectively. The obtained high response performances can be ascribed to the MgO HBL. Due to the energy band alignment between MgO and TiO 2 , photo-generated holes are effectively blocked to avoid their flowing back to FTO substrate to recombine with photoelectrons. While the wide band gap of MgO provides a favorable tunnel for electrons, thus resulting in less photocurrent loss between TiO 2 NPs and FTO substrate. Furthermore, MgO/TiO 2 NPs based UV PD shows significant UV light selectivity and stability. Consequently, the proposed holes blocking effect of MgO may pave a way to develop UV PDs with high efficiencies.

Characteristic Performance of OLED Based on Hole Injection, Transport and Blocking Layers

Background: Organic Light Emitting Diodes have emerged as a potential candidate for being used as the display because of their remarkable performance. In the past decade, a lot of interest was shown in their development and improvement. Scientists utilized different methods for enhancing their performance which included the change in OLEDs architecture. Different supporting layers (charge injection, transportation and blocking) are added in the architecture to enhance the performance of OLED. Some of the patents related to the application of the OLED have also been reviewed to observe the utilization of the present work in those applications. Objective: The motive of this research article is to analyze impacts the impact of different layers on the performance of OLED. Methods: The objective is achieved by systematically analyzing the impact of different layers on the OLED. The analysis commenced by investigating the properties of the basic OLED consisting of the emission layer only. Thereafter, in succession different supporting layers are added to the OLED architecture. Subsequently, after adding each layer, OLED device is analyzed and its properties are determined. Finally, the performance of different layers is compared. Results: The outcome of the above research study shows that these supporting layers are significantly able to enhance the performance of the OLED. Step by step layers are added to the architecture and enhancement in the performance is observed. There is an improvement of 13% to 38% not over the basic OLED architecture, but over the multilayered OLED device, which is already far better than the basic OLED. Conclusion: Therefore, from the analyses, it can be concluded that the different layers are significant for the OLED architecture and improve the performance of the OLED considerably.

Improved photovoltaic performance of CdTe-based solar cells: Roles of using a hole-blocking layer and nanoscale imaging of barrier height at interfaces

The performance of photovoltaic devices is hindered by the presence of barrier height at the interfaces as well as the presence of structural defects. CdTe solar cells, based on a CdS/CdTe heterojunction and CdCl2 vapour treatment, exhibit high efficiency. In this work, we show that the use of a hole-blocking layer has a potential to further increase the efficiency of CdTe-based cells. As a case study, we have fabricated multi-juncton CdTe-based solar cells on both pristine- and textured-silicon substrates. Here we use an n-type zinc tin oxide (ZTO) thin film as the transparent conducting oxide (TCO) layer and an n-type hole-blocking layer of MoO3 on a p-type CdTe:Cu absorber layer. In addition, we map the nanoscale barrier height at each interface, i.e. ZTO/MoO3 and MoO3/CdTe:Cu by Kelvin probe force microscopy (KPFM). We also investigate the real time photo-generated charge carrier dynamics across the heterojunctions using photo-KPFM which plays a major role in the cell efficiency. Quantitative analysis shows that barrier height between the interfaces decreases after light illumination. Based on these findings, we have fabricated solar cells on pristine- and textured-Si substrates and the maximum efficiency is found to be 8.2% for the textured-Si substrate. The present study demonstrates the fabrication of efficient hole-blocking CdTe-based solar cells and provides insights on how local barrier height affects their macroscopic performance.

Vanadium dioxide-zinc oxide stacked photocathodes for photo-rechargeable zinc-ion batteries.

The development of batteries that can be recharged directly by light, without the need for external solar cells or external power supplies, has recently gained interest for powering off-grid devices. Vanadium dioxide (VO2) has been studied as a promising photocathode for zinc-ion batteries because it can both store energy and harvest light. However, the efficiency of the photocharging process depends on electrode structure and charge transport layers. In this work, we report photocathodes using zinc oxide as an electron transport and hole blocking layer on top of which we synthesise VO2. The improved interface and charge separation in these photocathodes offer an improvement in photo-conversion efficiency from ∼0.18 to ∼0.51% compared to previous work on mixed VO2 photocathodes. In addition, a good capacity retention of ∼73% was observed after 500 cycles. The proposed stacked photocathodes reduce the battery light charging time by 3-fold and are therefore an important step towards making this technology more viable.

Enhanced Photovoltaic Properties of Perovskite Solar Cells by Employing Bathocuproine/Hydrophobic Polymer Films as Hole-Blocking/Electron-Transporting Interfacial Layers.

In this study, we improved the photovoltaic (PV) properties and storage stabilities of inverted perovskite solar cells (PVSCs) based on methylammonium lead iodide (MAPbI3) by employing bathocuproine (BCP)/poly(methyl methacrylate) (PMMA) and BCP/polyvinylpyrrolidone (PVP) as hole-blocking and electron-transporting interfacial layers. The architecture of the PVSCs was indium tin oxide/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/MAPbI3/[6,6]-phenyl-C61-butyric acid methyl ester/BCP based interfacial layer/Ag. The presence of PMMA and PVP affected the morphological stability of the BCP and MAPbI3 layers. The storage-stability of the BCP/PMMA-based PVSCs was enhanced significantly relative to that of the corresponding unmodified BCP-based PVSC. Moreover, the PV performance of the BCP/PVP-based PVSCs was enhanced when compared with that of the unmodified BCP-based PVSC. Thus, incorporating hydrophobic polymers into BCP-based hole-blocking/electron-transporting interfacial layers can improve the PV performance and storage stability of PVSCs.

Improvement of Energy Efficiency in Anode-Supported Proton Ceramic Fuel Cells By Lanthanum Tungstate Hole Blocking Layer

For efficient operation of proton ceramic fuel cell (PCFC), transport properties of hole and electron are important factors to be controlled as well as that of protons. Ba-based perovskite-type proton conductors have been used as typical electrolytes for the PCFCs because of their high proton conductivity. However, they also exhibit apparent hole conduction under oxidative atmospheres which causes leakage current through the electrolyte. The leakage current leads to not only a decrease in cell voltages but also a reduction of the energy efficiency since the leakage current cannot be utilized as electric power while hydrogen is consumed to generate protons and electrons. Therefore, a novel approach to suppress the leakage current has been required.Lanthanum tungstate (La28−x W4+x O54+3/2x ; LWO) with a high La/W ratio of 6.7 is one of the attractive proton conductors with a quite low hole conductivity. Though its proton conductivity is lower than the typical perovskite-type electrolytes, a high protonic transport number is attractive as a hole blocking layer for the PCFCs. An introduction of a thin LWO hole blocking layer on the Ba-based proton conductors with the high proton conductivity will suppress the leakage current by changing a profile of oxygen chemical potential in the electrolytes as we have proposed previously (Y. Matsuzaki et al., ECS Trans. 91, 1009-1018 (2019)).In this study, we explored the influence of the LWO hole blocking layer on the cell performances of PCFCs by theoretical calculations and experiments. In the theoretical calculations, a BZY|LWO bilayer cell model in which the LWO layer was located at the cathode side was employed. The calculations suggested that the bilayer structure not only improves efficiency but also gives flexibility to control the cell performance as required. Moreover, we experimentally investigated the performance of anode-supported cells with a BZY monolayer electrolyte and with a BZY|LWO bilayer electrolyte to elucidate the effect of the LWO layer.An LWO layer thickness (L LWO) dependence of the OCV in the BZY|LWO bilayer model was calculated based on the transport properties of BZY and LWO. Dependences of the energy efficiency and the power density with respect to a ratio of to a total electrolyte thickness (L total) of 10 μm were calculated for the model at a fixed external current density (I ext) of 250 mA/cm2 and at a fixed terminal voltage (V T) of 1.05 V, respectively. ε was defined by ε = V T I ext/V th I ion, where V th and I ion are a Nernst voltage and an ionic current density. We assumed the following operation conditions; operation temperature of 600 °C, 3% H2O + 97% H2 for anode gas, and 3% H2O + 19.4% O2 + 77.6 % Ar for cathode gas. In the experiments, a BZY monolayer electrolyte and a BZY|LWO bilayer electrolyte were prepared on NiO-BZY cermet substrates by the pulsed-laser deposition (PLD). La0.6Sr0.4Co0.2Fe0.8O3− d (LSCF) cathode was applied for both the cells. To suppress chemical reactions of LWO with BZY and LSCF, thin La-doped ceria (LDC) layers were introduced. The resulted structure of the monolayer cell and the bilayer cell were Ni-BZY|BZY(3.5 μm)|LSCF and Ni-BZY|BZY(3.5 μm)|LDC(40 nm)|LWO(1 μm)|LDC(40 nm)|LSCF, respectively. Cell performance tests were performed at 600 °C supplying 3% humidified H2 + Ar gas for the anode and 3% humidified 20% O2 + Ar gas for the cathode.The calculated OCV of the BZY monolayer model was 1.08 V and steeply increased up to 1.13 V by employing the thin LWO layer with L LWO/L total of 0.017 owing to suppression of the leakage current. Calculated dependences of ε and the power density for the model are shown in Fig.1. The efficiency and the power density showed a steep increase with increasing L LWO/L total. They showed the maximum values at certain L LWO/L total values, and then gradually decreased as L LWO/L total approached 1. This calculation result indicates that the cells exhibiting both the high ε and the high power density can be developed by employing the bilayer structure with the thin LWO hole blocking layer. Moreover, It is notable that, as the performance of the bilayer cell can be tuned by changing as presented in Fig. 1, the bilayer structure increases a degree of freedom for the design of the cells to satisfy various performance requirements. In the experiments, an enhancement of the OCV from 0.95 V for the BZY monolayer cell to 1.01 V for the bilayer cell was actually observed as suggested by the calculation. We consider that these theoretical calculations and experimental results present the effectiveness of the LWO hole blocking layer for the development of the high-performance PCFCs with high-design flexibility. Figure 1