1728 results about "Electron hole" patented technology

An organic light-emitting device comprises an anode, a cathode and an organic layer formed between the anode and the cathode, and the organic layer comprises a hole injection layer, a hole transmission area, an electron blocking layer, a light-emitting area and an electron transmission area. The hole transport region comprises a first material and a second material, the first material and the second material are sequentially evaporated to form two hole transport layers, and the first material is selected from a compound shown in the formula 1; and the second material is selected from a compound shown in a formula 2. According to the invention, the first material with a high refractive index is used as the first hole transport layer, the second material with a low refractive index is used as the second hole transport layer, and the structures of the first material and the second material are respectively limited at the same time. The invention overcomes the limitation of a single material or a simple mixed material in the aspects of hole transport and luminous efficiency. .

The invention relates to the technical field of semiconductor devices, in particular to a low-working-current-density green light Micro-LED epitaxial structure and a preparation method thereof. The epitaxial structure comprises a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer and a P-type semiconductor layer. The electron blocking layer is not arranged on the multi-quantum-well light-emitting layer, the multi-quantum-well light-emitting layer comprises four sub-layers including a first light blue light multi-quantum-well layer, a second blue light multi-quantum-well layer, a third green light multi-quantum-well layer and a fourth light blue light multi-quantum-well layer, and the In component content in the third green light multi-quantum-well layer is larger than that in other layers. The third cyan light multi-quantum well layer is a main light-emitting unit and is not provided with an electron blocking layer, so that the blocking effect on hole injection can be eliminated, the hole injection efficiency of the P-type semiconductor layer is remarkably improved, and the matching degree of electron hole concentration in a multi-quantum well light-emitting layer region is improved.

The invention relates to the technical field of preparation of organic photoelectric materials, in particular to a boron-nitrogen compound and an organic electroluminescent device comprising the same. The boron-nitrogen compound disclosed by the invention has good electron and hole receiving capability, and interaction among luminescent molecules can be effectively inhibited by introducing a large-steric-hindrance double-spiro group. Specifically, the boron-nitrogen compound provided by the invention is used as a functional layer, especially as an organic electroluminescent device manufactured by a luminescent layer, the current efficiency is improved, the efficiency of the device is greatly improved, and the service life of the device is greatly prolonged. Therefore, after most electrons and holes are compounded, energy is effectively transferred to the boron-nitrogen compound, so that high luminous efficiency is realized.

The invention provides a Cu2O-based heterogeneous composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: coating the surface of a Cu2O hollow sphere substrate with a carbon layer, and depositing layered double hydroxides (LDHs) and metal palladium (Pd) nanoparticles on the carbon layer. According to the material, through a Cu2O-carbon layer-LDHs-Pd multistage heterostructure design, space optimization of light absorption, charge transfer and catalytic sites is realized; cu2O-carbon layer-LDHs interface coupling promotes directed migration of photo-induced electron-hole pairs, and the surface plasmon resonance effect of Pd nanoparticles enhances the charge separation efficiency; the LDHs optimizes a charge transfer path through surface oxygen vacancy or metal valence cycle, so that synergistic oxidation of non-free radicals and free radicals is realized, the organic matter degradation efficiency is remarkably improved, the oxidation path is widened, and the performance bottleneck of a single material is broken through.

The invention provides a preparation method and application of a quantum dot light-emitting diode based on interface modification, and belongs to the technical field of quantum dot materials. The preparation method comprises the following steps: (1) spin-coating PEDOT: PSS-4083 on ITO (Indium Tin Oxide) to obtain a hole injection layer; (2) spin-coating polyvinyl carbazole on the hole injection layer in the step (1) to obtain a hole transport layer; (3) spin-coating pyridine on the hole transport layer in the step (2) to obtain a modification layer; (4) spin-coating ZnCdS / ZnS quantum dot normal octane on the modification layer in the step (3) to obtain a quantum dot film; and (5) spin-coating an Mg-doped ZnO ethanol solution on the quantum dot film in the step (4), and performing high-vacuum evaporation to obtain the quantum dot light-emitting diode. Compared with an original device, the EQE of the prepared quantum dot light emitting diode is improved by 16.5%, and the highest brightness is improved by 12.5%.

The invention discloses a thermal-decay-resistant red light Micro LED epitaxial structure and a preparation method thereof. The epitaxial structure sequentially comprises a substrate layer, an n-type buffer layer, an n-type etching barrier layer, an n-type ohmic contact layer, an n-type limiting layer, a quantum well structure, a p-type spacer layer, a p-type electron barrier layer and a p-type ohmic contact layer from bottom to top. Wherein the quantum well structure is formed by alternating 1-5 pairs of InGaP well layers and three-section type p-type AlGaInP barrier layers, and the three sections of barrier layers adopt gradient energy level design and are all subjected to p-type doping; according to the invention, the problems of carrier loss and low recombination efficiency at high temperature in the prior art are solved by blocking electron overflow through the gradient energy level barrier and supplementing the hole concentration through p-type doping, so that the 85 DEG C external quantum efficiency attenuation rate is less than or equal to 10%, the service life is prolonged to more than 50,000 hours, and the process is compatible with mass production and is suitable for the fields of display, illumination and the like.

The present invention relates to a metal complex having a structure of chemical formula (I). The metal complex is applied to an organic light-emitting device which emits deep red or near-infrared light, and shows a lower driving voltage and higher luminous efficiency, and has greatly prolonged service life. Therefore, the metal complex has the potential of being applied in the field of organic light-emitting devices. Also provided is an organic light-emitting device, including a cathode, an anode, and an organic layer. The organic layer is one or more of a hole injection layer, a hole transport layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer; and at least one layer in the organic layer contains the compound of structural formula (I).

The invention relates to the technical field of catalytic materials, and particularly discloses a visible light photocatalyst and a preparation method thereof.The visible light photocatalyst comprises a core layer-shell layer-dynamic regulation and control layer three-stage structure; the core layer is heterojunction nano-particles formed by bismuth vanadate and bismuth oxyiodide, and the bismuth vanadate particles are uniformly dispersed on the surface of the bismuth oxyiodide to form a p-n heterojunction; the molar ratio of bismuth vanadate to bismuth oxyiodide in the core layer is 1: (0.5-2), and the particle size range is 30-80 nm; through an elaborately designed three-level structure and a dynamic regulation and control mechanism, the response efficiency and environmental adaptability of the photocatalyst to visible light are remarkably improved. A built-in electric field is formed by utilizing the energy band matching characteristic of bismuth vanadate and bismuth oxyiodide, so that the separation of photo-induced electron-hole pairs is effectively promoted, and the absorption boundary of visible light is expanded to 650nm.

The invention relates to the technical field of preparation of organic photoelectric materials, in particular to a boron-nitrogen compound and an organic electroluminescent device comprising the same. The boron-nitrogen compound disclosed by the invention has good electron and hole receiving capability, and interaction among luminescent molecules can be effectively inhibited by introducing a spirocyclic group with large steric hindrance. Specifically, the boron-nitrogen compound provided by the invention is used as a functional layer, especially as an organic electroluminescent device manufactured by a luminescent layer, the current efficiency is improved, the efficiency of the device is greatly improved, and the service life of the device is greatly prolonged. Therefore, after most electrons and holes are compounded, energy is effectively transferred to the boron-nitrogen compound, so that high luminous efficiency is realized.

The invention relates to the technical field of electroluminescence, and discloses a laminated organic light-emitting device and application thereof, and the laminated organic light-emitting device comprises an anode layer, a first light-emitting unit, an electron transport layer, an interface modification layer, a connection layer, a second light-emitting unit and a cathode layer which are sequentially arranged from bottom to top; the electron transport layer comprises a hole blocking layer and an n-type electron transport layer; wherein the n-type electron transport layer is composed of an n-type dopant and an organic electron transport material, has the functions of electron transport, charge separation and injection and regulation and control of the optical microcavity effect of the laminated device, can simplify the electron transport and connection layer structure of the laminated device, and effectively improves the conductivity of the laminated device; according to the laminated organic light-emitting device, the voltage drop of the body is obviously reduced, and the interface electron injection barrier is reduced, so that the laminated organic light-emitting device has the advantages of low driving voltage, high efficiency and long service life, and the effect of adjusting the optical microcavity of the device can be achieved by utilizing the n-type electron transport layer.

The invention provides a modified positive electrode material and a preparation method and application thereof. The modified positive electrode material comprises a lithium manganese iron phosphate inner core and a coating layer coating the surface of the lithium manganese iron phosphate inner core, and the material of the coating layer comprises oxyfluoride; ti and S are co-doped in the lithium manganese iron phosphate core. Ti and S are co-doped in a lithium manganese iron phosphate core, Ti doping can introduce additional electron holes to enhance the intrinsic electron conductivity of the material, S doping can expand a lithium ion channel and improve the Li < + > diffusion rate, and the Ti doping and the S doping are synergistically optimized through two channels of electron conduction-ion migration, so that the rate capability and the cycling stability of the positive electrode material are improved; the oxyfluoride is adopted as a coating layer material, so that HF corrosion and dissolution of transition metal can be reduced, an interface side reaction is inhibited, meanwhile, the excellent thermal stability and wide electrochemical window of the oxyfluoride can inhibit decomposition and gas production of an electrolyte in a high-temperature environment, and the thermal stability and electrochemical stability of the modified positive electrode material are improved.

The invention relates to an energy storage type photo-generated cathode protection coating material and a preparation method thereof, and belongs to the technical field of chemical materials. The coating material is a binary composite material which is composed of nanometer MoO3 and BiVO4. The preparation method comprises the following steps: firstly, preparing nano MoO3 by a precipitation method, and then preparing a nano MoO3 and BiVO4 binary composite material in situ by a low-temperature hydrothermal method, namely the coating material disclosed by the invention. In the coating material, nano MoO3 and BiVO4 are adopted to form a heterojunction material, so that the photoresponse range of BiVO4 is widened, and the photoelectron-hole separation efficiency is effectively improved; meanwhile, nano MoO3 is used as an energy storage material with high theoretical specific capacity, part of photo-induced electrons generated by BiVO4 can be stored in the form of a compound, and in a dark state environment, the electrons stored in MoO3 are released and quickly transferred to the surface of metal or a film-forming substrate, so that cathode protection of the metal in the dark environment is realized; the technical problems that in the prior art, nano BiVO4 is low in electron-hole separation efficiency and poor in metal surface adhesive force, and the cathode protection effect cannot be continued in the dark state are solved.

A physics-based network model is trained to learn weights such as trapping, detrapping, and / or transport of holes and / or electrons, as well as voltage distribution on a voxel-by-voxel basis throughout a solid-state detector model. The physics-based network may be used to estimate material property variation throughout the voxels. To reduce the number of experimental setups and information needed to train the models, the models may be trained using more easily acquired ground truth. Just the electrode signals or just the free charge data is used to train the model to characterize the solid-state detector. With this reduced data, the detector may be characterized using equivalency, such as combining multiple trapping centers to an equivalent trapping center. Regularization may be used in the loss calculation, such as where just the electrode signals are used, to deal with the reduced data available as ground truth.

The invention provides an organic electrochemical transistor regulated and controlled by a grating electrode and a preparation method of the organic electrochemical transistor, and belongs to the technical field of photoelectric detection and organic electrochemical transistors. The organic electrochemical transistor comprises a transparent substrate, a detector anode, a hole transport layer, a photosensitive layer, a semiconductor active layer, an electron transport layer, a detector cathode, a packaging layer, a transistor grid electrode, a transistor source electrode, a transistor drain electrode and an electrolyte. A QPD and an OECT are integrated above the transparent substrate. The invention also provides a preparation method of the organic electrochemical transistor. Through the illumination effect, the photo-generated voltage generated by the QPD serves as a grid regulation and control signal, and higher current variation for different illumination intensities is achieved. The preparation process is remarkably simplified, the responsivity, the detectivity and the linear dynamic range of the device are improved, the stability and the low power consumption characteristic are improved, and a new solution is provided for application of a photoelectric-electrochemical fusion device in the fields of flexible electronics, wearable detection, biosensing and the like.

This invention relates to an aromatic amine organic compound and an organic electroluminescent device containing the same, belonging to the field of semiconductor materials technology. The structure of the compound provided by this invention is shown in general formula (1): When the hole transport material or electron blocking layer material of the organic electroluminescent device is prepared by using the aromatic amine compound of this invention, the device voltage can be reduced and the device life can be extended at the same time, especially the device high temperature life is significantly improved.

A light-emitting device includes a first electrode, a second electrode facing the first electrode, and an interlayer including an emission layer between the first electrode and the second electrode and a hole transport region between the first electrode and the emission layer, wherein the emission layer may include a dopant, the hole transport region may include a first hole transport layer, a second hole transport layer between the first hole transport layer and the emission layer, and a third hole transport layer between the second hole transport layer and the emission layer, the first hole transport layer may include a first compound, the second hole transport layer may include a second compound, the third hole transport layer may include a third compound, and the first to third compounds may each independently be an amine-based compound, but may be different from each other.

The invention relates to the technical field of semiconductor materials, in particular to a low-working-current-density cyan LED epitaxial structure and a preparation method thereof.The low-working-current-density cyan LED epitaxial structure comprises a substrate, and a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum-well light-emitting layer and a P-type semiconductor layer which are sequentially stacked on the substrate; the multi-quantum well light-emitting layer comprises a first light blue light multi-quantum well sub-layer, a second blue light multi-quantum well sub-layer, a third blue light multi-quantum well sub-layer and a fourth light blue light multi-quantum well sub-layer which are sequentially stacked and grown from bottom to top; wherein each sub-layer is of a superlattice structure of an InGaN multi-quantum well layer and a multi-quantum barrier layer, and the barrier heights of the sub-layers decrease progressively in a gradient mode, namely, the high barrier, the middle barrier, the low barrier and the low barrier decrease progressively in sequence. The upper-layer low-potential barrier attracts holes to migrate downwards, and the lower-layer high-potential barrier blocks electrons from leaking, so that space matching of the electrons and the holes is realized, and the performances such as luminous efficiency and yield of the cyan LED chip under low working current density are improved.

According to the deep ultraviolet laser epitaxial structure and the epitaxial growth method thereof provided by the invention, the Al component of the first waveguide layer is linearly and progressively increased from the side close to the electron injection layer to the side close to the quantum well active layer; or the Al component of the second waveguide layer is linearly and progressively decreased from the side close to the quantum well active layer to the side close to the hole injection layer to form refractive index distribution which takes the barrier layer of the quantum well active layer as the highest refractive index point and gradually decreases towards one side (the n-type side or the p-type side), so that the light field is firmly bound near the quantum well active layer, and the light limiting capability is remarkably enhanced; meanwhile, high-low Al components of the p-type side (the second waveguide layer) gradually change to generate a strong polarization electric field, ionization of a p-type doped acceptor (such as Mg) can be promoted, two-dimensional hole gas (2DHG) can be induced, and the hole concentration is improved; the low-high Al components of the n-type side (the first waveguide layer) are gradually changed, so that two-dimensional electron gas can be induced, and the electron concentration is improved.

According to one embodiment, a display device includes an anode, an organic EL element layer including a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer and an electron injection layer, and a cathode, wherein ΔE2_LUMO is defined as a potential barrier between the electron transport layer and the hole blocking layer, and the light-emitting layer, ΔE2_HOMO is defined as a potential barrier between the hole transport layer and the electron blocking layer, and the light-emitting layer, and each of ΔE2_LUMO and ΔE2_HOMO is 0.1 eV or higher and 0.5 eV or less.

The invention relates to the technical field of photo-anodes, in particular to a composite photo-anode with transition metal ions embedded into phosphoric acid small organic molecules and a preparation method of the composite photo-anode. The preparation method comprises the following steps: S1, soaking a bismuth vanadate photo-anode in a phosphoric acid small organic molecule solution, and then performing annealing treatment to obtain a phosphoric acid small organic molecule / photo-anode; and S2, soaking the phosphoric acid small organic molecule / photo-anode in a transition metal salt solution to obtain the composite photo-anode. According to the invention, hole storage and transmission functions of polyphosphoric acid small organic molecules and surface rapid water oxidation reaction kinetics of metal ions are synergistically utilized, on one hand, the electron-hole separation efficiency of bismuth vanadate is improved through hole storage, and on the other hand, surface hydroxyl groups of the polyphosphoric acid small organic molecules and transition metal ions are anchored; bismuth vanadate surface electron-hole separation and water oxidation kinetics are synergistically enhanced, charge recombination is synergistically inhibited, charge transfer power is promoted, and the photocurrent density and the water decomposition hydrogen production capacity of the photoanode are improved.

The invention relates to the technical field of semiconductor device design and simulation, in particular to a multi-physics-field coupled photoelectric detector modeling method and system, and the method comprises the steps: calculating the spatial distribution of the carrier generation rate, the carrier recombination rate, the potential, the distribution of electron concentration and hole concentration, and heat effect feedback data of a surface incidence semiconductor photoelectric detector; calculating the current density distribution of the target surface incident semiconductor photoelectric detector under the dynamic input optical power; based on an automatic differential Newton iteration method, a multi-physics field coupling equation set is solved according to spatial distribution of a carrier generation rate, current density distribution, a carrier recombination rate, potential, distribution of electron concentration and hole concentration and heat effect feedback data; and establishing an equivalent circuit model of the surface incidence semiconductor photoelectric detector, and carrying out co-simulation with an external circuit. Therefore, the problems of insufficient physical field coupling, poor numerical stability, low calculation efficiency, inaccurate simulation and the like in a traditional photoelectric detector simulation method are solved.

To provide a hole transporting material with which a photoelectric conversion element having solvent resistance and high light resistance can be manufactured.SOLUTION: There is provided a hole transporting material represented by the following general formula (1). In the general formula (1), X represents an aromatic hydrocarbon group that may have a substituent, and Y represents a pyridine group that may have a substituent.SELECTED DRAWING: None

The invention provides a compound with an electron transmission function, an organic electroluminescent device containing the compound and application of the compound, the structure of the compound takes 9-alkyl-9-phenyl fluorenyl, phenanthryl and a triazine group as main components, the 9-alkyl-9-phenyl fluorenyl is one of core structures, fluorene is a polycyclic aromatic hydrocarbon with better planarity, and the triazine group is one of the core structures. Alkyl and phenyl are introduced to the ninth site to generate strong spatial repulsive force with a fluorene ring, a three-dimensional and non-planar propeller-shaped structure is formed, and the non-planar structure can effectively inhibit close packing of molecules in a solid state, so that concentration quenching and excimer formation caused by pi-pi packing are prevented, and the stability of the fluorescent probe is improved. And moreover, the rigid and non-planar structure can also effectively improve the thermal stability of the material, and the service life of the device is prolonged. The compound provided by the invention is used as an electron transport layer and a hole blocking layer in a light-emitting device, so that the device has low driving voltage, high luminous efficiency and long service life.

The invention relates to the field of preparation of ultraviolet photoelectric detectors, in particular to a p-i-n type ultraviolet photoelectric detector based on a 4H-SiC-GaN heterostructure and a preparation method of the p-i-n type ultraviolet photoelectric detector based on the 4H-SiC-GaN heterostructure, the dislocation defect is greatly reduced on the material structure level, a foundation is built for subsequent high-quality crystal growth, it is ensured that the structure of the detector is stable under complex working conditions, and the performance of the detector is improved. Material damage caused by thermal expansion and cold contraction or lattice stress is effectively avoided, and the reliability and durability of the detector are greatly improved. And the preparation process is fine. The MOCVD technology is adopted for growth, and parameters of all links are accurately regulated and controlled. Furthermore, high-purity metal is matched with proper evaporation rate and deposition thickness, and is combined with a high-vacuum physical vapor deposition technology, so that good ohmic contact between the metal and a semiconductor is ensured, the hole injection efficiency is high, the carrier recombination probability is reduced, the photoelectric conversion efficiency is effectively improved, and the wide market prospect is achieved.

The invention relates to the technical field of semiconductor materials, in particular to a low-working-current-density green-light LED epitaxial structure and a preparation method thereof.The low-working-current-density green-light LED epitaxial structure comprises a substrate, and a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum-well light-emitting layer and a P-type semiconductor layer which are sequentially stacked on the substrate; the multi-quantum-well light-emitting layer comprises a first blue light multi-quantum-well layer, a second green light multi-quantum-well layer, a third green light multi-quantum-well layer and a fourth green light multi-quantum-well layer which are sequentially stacked and grown from bottom to top. Wherein each InGaN well layer and each quantum barrier layer are subjected to gradient design in thickness, Al component and In component, so that electron and hole space matching is realized, and the performances such as luminous efficiency and yield of the green light LED chip under low working current density are improved.

The utility model relates to a diagnostic imaging system and a radiation detector thereof. The radiation detector comprises an anode assembly, a cathode assembly, a conversion assembly and an irradiation assembly. In the diagnostic imaging system, radiation penetrates through the cathode assembly and reaches the conversion assembly, visible light and / or infrared light are / is emitted through the irradiation assembly to irradiate the conversion assembly, so that the radiation can be converted into electrons and holes in the conversion assembly, the electrons can be collected by the anode assembly, and the electrons are collected through the anode assembly. Therefore, the number change of electrons can be detected at the contact position of the signal generator and the anode assembly, the electrons can be converted into radiation site signals, radiation penetrating through a to-be-imaged object is detected, the transparent electrode is transparent to infrared light and / or visible light, the photoinduced quantum yield is increased, and the imaging quality is improved. The above effects improve the stability of the radiation detector in a radiation use environment.

The invention provides a carbazole ring-containing compound and an organic electroluminescent device thereof, and relates to the technical field of organic electroluminescent materials. The carbazole ring-containing compound provided by the invention has relatively high glass transition temperature and molecular thermal stability, and has a proper HOMO energy level, so that the distribution of electrons and holes in a luminescent layer is more balanced, and the recombination efficiency of excitons in the luminescent layer is improved; when the compound is applied to a light-emitting layer of an organic light-emitting device, the light-emitting efficiency and the service life of the device can be effectively improved. Meanwhile, the preparation method of the compound is simple, raw materials are easy to obtain, and the compound can be widely applied to the fields of organic thin film transistors, panel display and the like and has good application effects and industrialization prospects.

The invention relates to the technical field of preparation of organic photoelectric materials, in particular to a boron-nitrogen compound and an organic electroluminescent device comprising the same. The boron-nitrogen compound disclosed by the invention has good electron and hole receiving capability, and interaction among luminescent molecules can be effectively inhibited by introducing large-steric-hindrance azafluorene / benzfluorene / azabenzfluorene / silafluorene / germanium heterofluorene and other groups. The energy transmission performance between a subject and an object or a sensitizer can be improved by a large conjugated spiro structure unit, an sp2 aza-aromatic ring and other structures. Specifically, the boron-nitrogen compound provided by the invention is used as a functional layer, especially as an organic electroluminescent device manufactured by a luminescent layer, the current efficiency is improved, the lighting voltage is reduced, and meanwhile, the service life of the device is greatly prolonged. Therefore, after most electrons and holes are compounded, energy is effectively transferred to the boron-nitrogen compound, so that high luminous efficiency is realized.

The invention belongs to the technical field of solar cells, and discloses a back contact double-sided perovskite solar cell based on a parallel structure and a preparation method of the back contact double-sided perovskite solar cell. The battery comprises, in order: a glass substrate; a first perovskite light absorption layer; the first charge transport layer comprises a first hole transport layer HTL and a first electron transport layer ETL which are arranged at an interval; patterning the electrode layer; the second charge transport layer comprises a second hole transport layer HTL and a second electron transport layer ETL which are arranged at an interval, the second hole transport layer HTL and the first hole transport layer HTL are correspondingly arranged, and the second electron transport layer ETL and the first electron transport layer ETL are correspondingly arranged; patterning the insulating layer; a second perovskite light absorption layer; and packaging the adhesive film layer and the back glass. According to the solar cell, double-face light receiving and maximum light energy utilization can be achieved, meanwhile, the requirement for current matching is lowered through the parallel connection design, the shadow tolerance and environmental adaptability of a device are improved, and the manufacturing cost is reduced.

A light-emitting device includes a first electrode, and second electrode facing the first electrode, and an interlayer between the first electrode and the second electrode. The interlayer includes an emission layer and a layer. The emission layer includes a first hole transport compound, a first electron transport compound, and a third compound. The layer includes the first electron transport compound, a metal-containing material, and a second electron transport compound, and the layer is between the emission layer and the second electrode.