OLED devices and electronic devices

Abstract

This invention provides an OLED device and an electronic device. The OLED device includes an anode, a cathode, and a light-emitting layer disposed between the anode and the cathode. Multiple light-emitting sublayers include: a first light-emitting sublayer configured as the main recombination region of electrons and holes; and a second light-emitting sublayer disposed adjacent to the first light-emitting sublayer. The triplet energy level of the host material in the second light-emitting sublayer is lower than that in the first light-emitting sublayer, causing triplet excitons generated in the first light-emitting sublayer to migrate to the second light-emitting sublayer. The second light-emitting sublayer is used to induce triplet-triplet annihilation of the migrated triplet excitons to generate singlet excitons. The OLED device of this invention, by setting multiple light-emitting sublayers to form an energy level gradient, guides the directional migration of triplet excitons, achieving spatial separation of excitons and polarons and local convergence of triplet excitons, thereby improving luminous efficiency by more than 10% and extending lifespan by more than 10%.

Description

Technical Field

[0001] This invention belongs to the field of electronic device technology, specifically relating to an OLED device and an electronic device. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are light-emitting devices that directly convert electrical energy into light energy using organic materials. In OLED devices, the emissive layer typically comprises a host material and light-emitting dopants, emitting light through exciton formation via carrier recombination. Blue OLED devices still suffer from shortcomings in efficiency and lifetime; for example, the interaction between triplet excitons and polarons leads to energy dissipation and material aging. Therefore, improving the luminous efficiency and lifetime of blue OLED devices is a pressing technical challenge in this field. Summary of the Invention

[0003] This invention aims to at least solve the problem of reduced efficiency and shortened lifetime caused by the triplet-polaron quenching effect in the prior art, and proposes an OLED device and electronic device.

[0004] To achieve the objectives of this invention, an OLED device is provided, comprising an anode, a cathode, and a light-emitting layer disposed between the anode and the cathode. The light-emitting layer comprises a host material and a light-emitting dopant, and includes a plurality of light-emitting sub-layers, wherein the plurality of light-emitting sub-layers include:

[0005] The first photonic layer is configured as the main recombination region of electrons and holes for generating excitons, which include singlet excitons and triplet excitons;

[0006] The second light-emitting sublayer is located on the side of the first light-emitting sublayer closer to the cathode and is disposed adjacent to the first light-emitting sublayer. The triplet energy level of the main material in the second light-emitting sublayer is lower than the triplet energy level of the main material in the first light-emitting sublayer, so that the triplet excitons generated in the first light-emitting sublayer migrate to the second light-emitting sublayer.

[0007] The second luminescent layer is used to generate singlet excitons by causing triplet-triplet annihilation of the triplet excitons that migrate therein.

[0008] In some embodiments, the plurality of light-emitting sublayers further include:

[0009] The third light-emitting sublayer is located on the side of the second light-emitting sublayer closer to the cathode and is disposed adjacent to the second light-emitting sublayer. The triplet energy level of the main material in the third light-emitting sublayer is higher than the triplet energy level of the main material in the second light-emitting sublayer and lower than the triplet energy level of the main material in the first light-emitting sublayer.

[0010] In some embodiments, the first, second, and third light-emitting sublayers comprise a host material and a light-emitting dopant, wherein the triplet energy level of the light-emitting dopant is higher than that of the host material.

[0011] The triplet energy level of the host material of the first luminescent sublayer is higher than that of the host material of the third luminescent sublayer.

[0012] The triplet energy level of the host material of the third luminescent sublayer is higher than that of the host material of the second luminescent sublayer, and the triplet energy level difference of the host materials of adjacent luminescent sublayers is greater than 0.2 eV.

[0013] In some embodiments, the singlet energy level of the luminescent dopant in the plurality of luminescent sublayers is lower than the singlet energy level of the host material in the luminescent sublayer, and the difference between the singlet energy level and the host material in the luminescent sublayer is greater than 0.2 eV.

[0014] In some embodiments, the thickness of the first luminescent sublayer is 30 Å-70 Å; and / or, the thickness of the second luminescent sublayer is 10 Å-40 Å; and / or, the total thickness of the first luminescent sublayer, the second luminescent sublayer, and the third luminescent sublayer is 150 Å-250 Å.

[0015] In some embodiments, the plurality of light-emitting sublayers further include:

[0016] The Nth luminescent sublayer, where N is a positive integer greater than 3, is located on the side of the third luminescent sublayer closer to the cathode. The Nth luminescent sublayer is adjacent to the (N-1)th luminescent sublayer, and the triplet energy level of the host material in the Nth luminescent sublayer is higher than the triplet energy level of the host material in the (N-1)th luminescent sublayer but lower than the triplet energy level of the host material in the first luminescent sublayer.

[0017] In some embodiments, among the plurality of light-emitting sublayers, starting from the first light-emitting sublayer, the odd-numbered light-emitting sublayers contain a host material and a light-emitting dopant, and the even-numbered light-emitting sublayers contain only the host material.

[0018] In some embodiments, the thickness of the even-numbered light-emitting sublayer is less than 30 Å.

[0019] In some embodiments, the concentration of the light-emitting dopant in the first light-emitting sublayer is higher than the concentration of the light-emitting dopant in the other odd-numbered light-emitting sublayers.

[0020] In some embodiments, the concentration of the light-emitting dopant in the first light-emitting sublayer is 1%-3%, and / or the concentration of the light-emitting dopant in the odd-numbered light-emitting sublayers other than the first light-emitting sublayer is 0.5%-1.5%.

[0021] In some embodiments, the triplet energy level of the host material in the odd-numbered light-emitting sublayer is not lower than the triplet energy level of the host material in the even-numbered light-emitting sublayer.

[0022] In some embodiments, the triplet energy level of the host material in the first luminescent sublayer is higher than the triplet energy level of the host material in the other luminescent sublayers.

[0023] In some embodiments, the triplet energy level difference between the host material in the first luminescent sublayer and the host material in the second luminescent sublayer is greater than 0.2 eV.

[0024] In some embodiments, the triplet energy level of the luminescent dopant in the luminescent sublayer is higher than the triplet energy level of the host material in the luminescent sublayer, and the singlet energy level of the luminescent dopant in the luminescent sublayer is lower than the singlet energy level of the host material in the luminescent sublayer.

[0025] According to another aspect of the present invention, an electronic device comprising the aforementioned OLED device is also disclosed.

[0026] The OLED device of this invention, by setting multiple light-emitting sub-layers and ensuring that the triplet energy level of the host material in the second light-emitting sub-layer is lower than that in the first light-emitting sub-layer, forms an energy level gradient. This gradient guides the directional migration of triplet excitons, achieving spatial separation of excitons and polarons, as well as localized aggregation of triplet excitons. This results in an increase in luminous efficiency of over 10% and a lifespan extension of over 10%. Simultaneously, due to the effective aggregation of triplet excitons, the efficiency stability of the device under different current densities is also improved. The FTT effect is significant at low current densities, while the efficiency roll-off phenomenon is suppressed at high current densities.

[0027] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments provided herein, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily apparent from the following description. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an OLED device according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the formation of singlet and triplet excitons by excitons according to an embodiment of the present invention;

[0030] Figure 3This is a schematic diagram of the structure of the light-emitting layer of an OLED device according to an embodiment of the present invention;

[0031] Figure 4 for Figure 3 The graph shows a comparison of the luminous efficiency of the OLED device in the embodiment with that of a traditional single-layer light-emitting layer structure.

[0032] Figure 5 This is a schematic diagram of the structure of the light-emitting layer of an OLED device according to another embodiment of the present invention;

[0033] Figure 6 for Figure 5 The graph shows a comparison of the luminous efficiency of the OLED device in the illustrated embodiment with that of a traditional single-layer light-emitting layer structure. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the OLED devices and electronic devices provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0035] In OLED devices, carrier injection and transport are prerequisites for light emission. An emissive layer for light emission is placed between the anode and cathode. Between the anode and emissive layer, a hole injection layer (HIL), a hole transport layer (HTL), and an electron blocking layer (EBL) are typically placed. The EBL blocks electrons from entering the hole transport region from the emissive layer. Between the cathode and emissive layer, an electron injection layer (EIL), an electron transport layer (ETL), and a hole blocking layer (HBL) are typically placed. The HBL blocks holes from entering the electron transport region from the emissive layer, while the ETL transports electrons to the emissive layer. Specifically, the HOMO level of the electron blocking layer (EBL) is typically located between the hole transport layer and the bulk material of the first emissive layer, and its LUMO level is higher than that of the bulk material of the first emissive layer to effectively prevent electron overflow while ensuring smooth hole injection. When a voltage is applied between the anode (such as an ITO anode) and the cathode (such as a metal cathode), holes are injected from the anode and move through the hole injection layer (HIL) and hole transport layer (HTL) to the light-emitting layer (EML); electrons are injected from the cathode and move through the electron injection layer (EIL) and electron transport layer (ETL) to the light-emitting layer. In organic materials, the injected electrons or holes cause the surrounding molecules to polarize due to their charge, forming "electron polarons" or "hole polarons".

[0036] When electron polarons and hole polarons meet in the luminescent layer, they recombine to form excitons. An exciton is an electron-hole pair in an excited state. Based on the combination of electron spin directions, excitons can be divided into two categories: singlet excitons (S1) and triplet excitons (T1). Under electrically excited conditions, the formation ratio of singlet excitons to triplet excitons is approximately 1:3. Singlet excitons have a short lifetime (nanoseconds), and their energy can be transferred to the luminescent dopant via Förster energy transfer (FRET, a long-range energy transfer mechanism based on dipole-dipole resonance, typically with a range of 10 Å to 100 Å, depending on the overlap of the donor emission spectrum and the acceptor absorption spectrum). This causes the dopant molecules to transition to an excited state, subsequently de-excited, and emit fluorescence. Triplet excitons have long lifetimes (microseconds to milliseconds). Due to spin forbiddenness, they cannot emit light directly through radiative transitions. Their energy is usually dissipated non-radiatively or transferred to other molecules through Dexter energy transfer (a short-range energy transfer mechanism based on electron exchange, with a working distance usually less than 10 Å, requiring overlap of the molecular orbitals of the donor and acceptor, and requiring the triplet energy level of the donor to be higher than or equal to that of the acceptor).

[0037] The luminescent layer typically consists of a host material and luminescent dopants dispersed within it. The host material occupies most of the volume of the luminescent layer, responsible for carrier transport and providing a site for exciton formation; the luminescent dopants act as luminescent centers, receiving energy from the host material and ultimately emitting light. The energy transfer mechanism between the host material and the luminescent dopants depends on the exciton type: singlet excitons primarily undergo Förster energy transfer, which has a relatively long range (10 Å ~ 100 Å) and depends on the overlap between the donor emission spectrum and the acceptor absorption spectrum; triplet excitons undergo Dexter energy transfer, which requires overlap of intermolecular electron clouds, has an extremely short range (< 10 Å), and requires the triplet energy level of the donor to be higher than or equal to the triplet energy level of the acceptor.

[0038] Triplet-triplet annihilation (TTA), also known as triplet fusion (TTF), is an important mechanism for improving the efficiency of fluorescent devices. This process involves the interaction of two triplet excitons after a collision, where one triplet exciton transfers energy to the other, causing it to transition to a higher energy level and relax to a singlet state, ultimately generating a light-emitting singlet exciton. The probability of TTT occurring is proportional to the square of the triplet exciton concentration; therefore, increasing the local concentration of triplet excitons is key to enhancing TTT efficiency.

[0039] In blue OLED devices based on related technologies, the emissive layer typically employs a single-layer structure or a simple multi-layer structure, such as a stacked architecture of anode / hole transport layer / emissive layer / electron transport layer / cathode. Taking a typical structure as an example, an electron blocking layer (EBL) is placed between the hole transport layer (HTL) and the emissive layer (EML) to prevent electron overflow while injecting holes into the emissive layer. Since the host material of the emissive layer usually has a higher electron mobility than hole mobility, and there is a HOMO energy level difference between the EBL material and the host material (BH) on the side of the emissive layer closer to the EBL, the recombination region of electrons and holes is confined to the vicinity of the interface between the EBL and the emissive layer. That is, after electrons rapidly pass through the entire emissive layer from the electron transport layer side, they meet and recombine with holes that are blocked by the HOMO energy level difference at the EBL / EML interface.

[0040] Within the aforementioned recombination region, holes accumulate in large numbers at the interface due to energy level hindrance, forming a high-density hole polaron. Simultaneously, a large number of excitons (including singlet and triplet excitons) generated by the recombination of electrons and holes are also concentrated in this narrow space. This results in triplet excitons and hole polarons being in a highly overlapping region, leading to a triplet-polaron quenching (TPQ) effect: the energy of the triplet exciton is transferred to the hole polaron in a non-radiative manner, causing the exciton energy to dissipate as heat and become unusable for luminescence. Simultaneously, this energy transfer process is accompanied by the release of high-energy particles exceeding 4.5 eV. These high-energy particles can damage the molecular structure of organic materials, leading to material degradation and accelerating device aging. Therefore, the TPQ effect simultaneously reduces device luminescence efficiency and shortens its lifespan.

[0041] On the other hand, triplet fusion (TTF), a key mechanism for improving efficiency by utilizing triplet energy, relies on the high concentration of triplet excitons. In related technologies, triplet excitons are dispersed throughout the emitting layer, making it difficult to form a high concentration sufficient to efficiently induce FTT in a specific region. Even if some triplet excitons undergo FTT, the conversion efficiency is far below the theoretical upper limit, with most triplet energy dissipated in non-radiative forms. Furthermore, at high current densities, the exciton generation rate increases, but the recombination region width is limited, and the uneven distribution of triplet exciton concentration leads to a further decrease in FTT efficiency, resulting in an efficiency roll-off phenomenon in the device.

[0042] In summary, the main problems in the relevant technologies are as follows: On the one hand, the spatial overlap between triplet excitons and polarons caused by the concentration of the composite region leads to the TPQ effect, which directly reduces efficiency and damages the material; on the other hand, the dispersed distribution of triplet excitons results in low FTT efficiency and an inability to effectively recover triplet energy. These two problems overlap, making it difficult for blue OLED devices to simultaneously achieve high efficiency, long lifespan, and good efficiency stability.

[0043] To address the above problems, the present invention provides an OLED device, such as... Figure 1 As shown, it includes an anode (not shown), a cathode (not shown), and a light-emitting layer 100 disposed between the anode and the cathode. A hole injection layer (not shown), a hole transport layer (not shown), and an electron blocking layer 200 are sequentially disposed between the anode and the light-emitting layer 100. An electron injection layer (not shown), an electron transport layer 300, and a hole blocking layer 400 are typically disposed between the cathode and the light-emitting layer 100. The light-emitting layer 100 includes a host material BH1 and a light-emitting dopant BD. The light-emitting layer 100 includes multiple light-emitting sublayers, including a first light-emitting sublayer 110 and a second light-emitting sublayer 120.

[0044] The first luminescent layer 110 is configured as the primary recombination region for electrons and holes, used to generate excitons, including singlet excitons S1 and triplet excitons T1. The second luminescent layer 120 is located on the cathode side of the first luminescent layer 110, adjacent to it, and the triplet energy level of the host material BH2 in the second luminescent layer 120 is lower than that of the host material BH1 in the first luminescent layer 110. This energy level relationship allows the triplet excitons T1 generated in the first luminescent layer 110 to spontaneously migrate to the second luminescent layer 120. The second luminescent layer 120 is used to induce triplet fusion (TTF) of the migrated triplet excitons T1 to generate singlet excitons S1.

[0045] When a voltage is applied between the anode and cathode, holes are injected from the anode and move towards the light-emitting layer 100 via the hole injection layer and hole transport layer between the anode and the light-emitting layer 100; electrons are injected from the cathode and move towards the light-emitting layer 100 via the electron injection layer and electron transport layer 300 between the cathode and the light-emitting layer 100. Since the bulk material of the light-emitting layer 100 typically has a higher electron mobility than hole mobility, and there is a HOMO energy level difference between the electron blocking layer 200 on the anode side and the first light-emitting sublayer 110, the recombination region of electrons and holes is confined within the first light-emitting sublayer 110. Therefore, the first light-emitting sublayer 110 becomes the main recombination region for electrons and holes.

[0046] In the first photonic layer 110, such as Figure 2 As shown, electrons and holes recombine to form excitons, of which singlet excitons S1 account for about 25% and triplet excitons T1 account for about 75%. Singlet excitons S1 have a short lifetime, and their energy is directly transferred to the luminescent dopant BD in the first luminescent layer 110 via Förster energy transfer, causing the luminescent dopant BD molecules to jump to an excited state, and then de-excite and emit fluorescence.

[0047] Triplet exciton T1 has a long lifetime and cannot emit light directly due to spin forbiddenness. According to the principle of minimum energy, triplet exciton T1 tends to migrate to lower energy regions. Since the triplet energy level of the host material BH2 in the second emitting sublayer 120 is lower than that of the host material BH1 in the first emitting sublayer 110, and the energy difference between adjacent levels is greater than 0.2 eV, forming a sufficient energy drop, therefore, if... Figure 1 and Figure 3 As shown, triplet excitons T1 generated in the first luminescent layer 110 spontaneously migrate to the second luminescent layer 120 via Dexter energy transfer. Once inside the second luminescent layer 120, the triplet excitons T1 are trapped there and find it difficult to return to the first luminescent layer 110.

[0048] As triplet excitons T1 accumulate in the second photonic layer 120, their local concentration significantly increases. Since the probability of triplet-triplet annihilation is proportional to the square of the triplet exciton T1 concentration, a high concentration of triplet excitons T1 substantially increases the probability of the TTF reaction. Two triplet excitons T1 merge through collision to generate a singlet exciton S1. This newly generated singlet exciton S1 then transfers its energy to the luminescent dopant BD in the second photonic layer 120 via Förster energy transfer, causing it to emit light. In this way, triplet energy, which was originally unusable, is converted into luminescent singlet energy, thereby improving the luminescent efficiency of the device.

[0049] Meanwhile, as the triplet exciton T1 migrates to the second photonic layer 120, while the first photonic layer 110, as the main recombination region, still contains a large number of polarons (especially hole polarons), the triplet exciton T1 and polarons are spatially separated. This spatial separation effectively suppresses the triplet-polaron quenching (TPQ) effect, reduces energy dissipation and material damage caused by TPQ, and thus extends the device's lifespan.

[0050] The OLED device of this invention, by setting multiple light-emitting sub-layers and ensuring that the triplet energy level of the host material BH2 in the second light-emitting sub-layer 120 is lower than that of the host material BH1 in the first light-emitting sub-layer 110, forms an energy level gradient. This guides the directional migration of triplet excitons T1, achieving spatial separation of excitons and polarons and local aggregation of triplet excitons T1, thereby improving luminous efficiency by more than 10% and extending lifespan by more than 10%. Simultaneously, due to the effective aggregation of triplet excitons T1, the efficiency stability of the device under different current densities is also improved; the TTF effect is significant at low current densities, and the efficiency roll-off phenomenon is suppressed at high current densities.

[0051] In some embodiments, the thickness of the first luminescent sublayer 110 is 30 Å-70 Å, and the thickness of the second luminescent sublayer 120 is 10 Å-40 Å. Setting the thickness of the first luminescent sublayer 110 to 30 Å-70 Å ensures that its thickness is greater than the broadband of direct recombination luminescence but less than the limit of Dexter energy transfer, thereby guaranteeing efficient exciton formation and avoiding energy loss. The smaller thickness of the second luminescent sublayer 120 facilitates efficient trapping of triplet excitons and increases their local concentration.

[0052] It should be noted that in some embodiments, the thickness of the first luminescent sublayer 110 is 30 Å-70 Å and the thickness of the second luminescent sublayer 120 is 10 Å-40 Å. However, this is not limiting. In some other embodiments, the thickness of the first luminescent sublayer 110 may be 30 Å-70 Å or the thickness of the second luminescent sublayer 120 may be 10 Å-40 Å. This application does not impose any limitations on these embodiments.

[0053] Furthermore, the singlet energy level of the luminescent dopant in multiple luminescent sublayers can be lower than the singlet energy level of the host material in the luminescent sublayer, and the difference between the singlet energy level and the host material in each luminescent sublayer is greater than 0.2 eV.

[0054] Specifically, in some embodiments, the plurality of light-emitting sub-layers further include: a third light-emitting sub-layer 130, which is located on the side of the second light-emitting sub-layer 120 near the cathode and is disposed adjacent to the second light-emitting sub-layer 120. The triplet energy level of the host material BH3 in the third light-emitting sub-layer 130 is higher than the triplet energy level of the host material BH2 in the second light-emitting sub-layer 120 and lower than the triplet energy level of the host material BH1 in the first light-emitting sub-layer 110.

[0055] At high current densities, the second emitting sublayer 120 may tend to saturate. Although the triplet energy level of the host material BH3 in the third emitting sublayer 130 is higher than that of the host material BH2 in the second emitting sublayer 120, it is still lower than that of the host material BH1 in the first emitting sublayer 110. Therefore, excess triplet excitons T1 can continue to migrate to the third emitting sublayer 130. After entering the third emitting sublayer 130, triplet excitons T1 can also undergo a TTF reaction to generate singlet excitons S1 and emit light, thus ensuring the efficiency gain at high current densities.

[0056] Figure 4 This is a comparison curve of the luminous efficiency of the OLED device according to an embodiment of the present invention with that of a traditional single-layer light-emitting layer structure, as shown in the figure. Figure 4 As shown, curve A represents Figure 3The luminous efficiency of the illustrated embodiment is shown in curve B, which represents the luminous efficiency of a traditional single-layer light-emitting layer structure. Curve C represents the efficiency ratio of this embodiment to the traditional single-layer light-emitting layer structure at various current densities. It can be seen that... Figure 3 The embodiment shown has a higher luminous efficiency than the traditional single-layer light-emitting layer structure at all current densities, and the efficiency ratio curve shows a significant improvement in efficiency over a wide current density range.

[0057] The OLED device using the embodiments of the present invention achieves a luminous efficiency improvement of over 10% and a lifespan extension of over 10%. Simultaneously, due to the effective focusing of triplet excitons T1, the efficiency stability of the device under different current densities is also improved; the TTF effect is significant at low current densities, and the efficiency roll-off phenomenon is effectively suppressed at high current densities.

[0058] Understandably, in some embodiments, the triplet energy level of the luminescent dopant in the luminescent sublayer is higher than the triplet energy level of the host material in the luminescent sublayer, and the triplet energy level difference between adjacent host materials in the luminescent sublayer is greater than 0.2 eV, to ensure that the triplet exciton T1 effectively moves to the adjacent host material with a lower triplet energy level. Similarly, the singlet energy level of the luminescent dopant in multiple luminescent sublayers is lower than the singlet energy level of the host material in the luminescent sublayer, and the energy difference between the singlet energy level and the host material in the luminescent sublayer is greater than 0.2 eV, to ensure that the singlet exciton S1 effectively activates the luminescent dopant.

[0059] In some embodiments, the total thickness of the first light-emitting sublayer 110, the second light-emitting sublayer 120, and the third light-emitting sublayer 130 is 150 Å to 250 Å. In other words, the total thickness of the first light-emitting sublayer 110, the second light-emitting sublayer 120, and the third light-emitting sublayer 130 is 150 Å to 250 Å.

[0060] like Figure 5 Another embodiment shown also provides an OLED device, which is similar to... Figures 1 to 4 The embodiments shown have the same structural components, including an anode, a cathode, and a light-emitting layer 100 disposed between the anode and the cathode. The light-emitting layer 100 includes a host material and a light-emitting dopant. The light-emitting layer 100 includes multiple light-emitting sublayers, including a first light-emitting sublayer 110, a second light-emitting sublayer 120, and a third light-emitting sublayer 130.

[0061] and Figure 2Similar to the illustrated embodiment, the first luminescent sublayer 110 is configured as the primary recombination region of electrons and holes to generate excitons, including singlet excitons S1 and triplet excitons T1. The second luminescent sublayer 120 is located on the cathode side of the first luminescent sublayer 110, adjacent to it, and the triplet energy level of the host material BH2 in the second luminescent sublayer 120 is lower than the triplet energy level of the host material BH1 in the first luminescent sublayer 110. The third luminescent sublayer 130 is located on the cathode side of the second luminescent sublayer 120, adjacent to it, and the triplet energy level of the host material BH3 in the third luminescent sublayer 130 is higher than the triplet energy level of the host material BH2 in the second luminescent sublayer 120 but lower than the triplet energy level of the host material BH1 in the first luminescent sublayer 110.

[0062] Figure 5 Another embodiment shown is similar to Figures 1 to 4 The embodiment shown differs in that the multilayer structure of the light-emitting layer 100 is further extended.

[0063] In some embodiments, the plurality of light-emitting sublayers further includes an Nth light-emitting sublayer, where N is a positive integer greater than 3. The Nth light-emitting sublayer is located on the side of the third light-emitting sublayer 130 near the cathode, and is disposed adjacent to the (N-1)th light-emitting sublayer. The triplet energy level of the host material in the Nth light-emitting sublayer is higher than the triplet energy level of the host material in the (N-1)th light-emitting sublayer but lower than the triplet energy level of the host material in the first light-emitting sublayer.

[0064] Specifically, taking N=5 as an example, the multiple light-emitting sublayers also include a fourth light-emitting sublayer 140 and a fifth light-emitting sublayer 150. The fourth light-emitting sublayer 140 is arranged adjacent to the third light-emitting sublayer 130, and the fifth light-emitting sublayer 150 is arranged adjacent to the fourth light-emitting sublayer 140. The main material BH in the Nth light-emitting sublayer is... N The triplet energy level is higher than that of the host material BH in the (N-1)th luminescent sublayer. N-1 The triplet energy level of the main material BH4 in the fourth luminescent sublayer 140 is higher than that of the main material BH3 in the third luminescent sublayer 130 and lower than that of the main material BH1 in the first luminescent sublayer 110. The triplet energy level of the main material BH5 in the fifth luminescent sublayer 150 is higher than that of the main material BH4 in the fourth luminescent sublayer 140 and lower than that of the main material BH1 in the first luminescent sublayer 110.

[0065] In some embodiments, the multiple light-emitting sublayers have alternating material compositions. Specifically, starting from the first light-emitting sublayer 110, the odd-numbered light-emitting sublayers contain both a host material and a light-emitting dopant; that is, the odd-numbered light-emitting sublayers are a mixed film of the host material and the light-emitting dopant formed by a co-evaporation process. Starting from the second light-emitting sublayer 120, the even-numbered light-emitting sublayers contain only the host material. That is:

[0066] The first luminescent sublayer 110 contains the host material BH1 and the luminescent dopant BD; the second luminescent sublayer 120 contains only the host material BH2; the third luminescent sublayer 130 contains the host material BH3 and the luminescent dopant BD; the fourth luminescent sublayer 140 contains only the host material; the fifth luminescent sublayer 150 contains both the host material and the luminescent dopant, and so on.

[0067] Starting from the second luminescent sublayer 120, the thickness of the even-numbered luminescent sublayers (i.e., luminescent sublayers containing only the host material) is less than 30 Å.

[0068] In some embodiments, the concentration of the light-emitting dopant BD in the first light-emitting sublayer 110 is higher than the concentration of the light-emitting dopant BD in the other odd-numbered light-emitting sublayers excluding the first light-emitting sublayer 110. Specifically, the concentration of the light-emitting dopant BD in the first light-emitting sublayer 110 is 1%-3%, and the concentration of the light-emitting dopant BD in the other odd-numbered light-emitting sublayers is 0.5%-1.5%. For example, in the case of three light-emitting sublayers, the concentration of the light-emitting dopant BD in the third light-emitting sublayer 130 is 0.5%-1.5%. As another example, in the case of five or six light-emitting sublayers, the concentration of the light-emitting dopant BD in the third light-emitting sublayer 130 and the fifth light-emitting sublayer 150 is 0.5%-1.5%. In this way, the first light-emitting sublayer 110, as the main recombination light-emitting region, has a higher concentration of the light-emitting dopant BD, which is beneficial for improving luminous efficiency and device lifetime; the subsequent odd-numbered layers mainly carry the carrier transport function, and their light-emitting dopant BD concentrations are set lower to avoid hindering carrier transport.

[0069] In some embodiments, the triplet energy level of the host material in the odd-numbered emitting sublayer is not lower than the triplet energy level of the host material in the even-numbered emitting sublayer. For example, the triplet energy level of the host material BH3 in the third emitting sublayer 130 is not lower than the triplet energy level of the host material BH2 in the second emitting sublayer 120, and the triplet energy level of the host material BH5 in the fifth emitting sublayer 150 is not lower than the triplet energy level of the host material BH4 in the fourth emitting sublayer 140.

[0070] The triplet energy level of the host material BH1 in the first luminescent sublayer 110 is higher than that of the host materials in the other luminescent sublayers. In particular, the triplet energy level difference between the host material BH1 in the first luminescent sublayer 110 and the triplet energy level of the host material in the second luminescent sublayer 120 is greater than 0.2 eV.

[0071] The following combination Figure 5 The working principle of another embodiment of the OLED device will be described in detail.

[0072] When electrons and holes recombine in the first luminescent layer 110 to generate excitons, singlet excitons S1 directly cause the luminescent dopant BD in the first luminescent layer 110 to emit light. Triplet excitons T1 migrate downwards along the energy level gradient. Since the triplet energy level of the host material BH2 in the second luminescent layer 120 is lower than that of the first luminescent layer 110, triplet excitons T1 migrate to the second luminescent layer 120 first.

[0073] The second luminescent layer 120 is a pure host layer containing only the host material BH2 and does not contain the luminescent dopant BD. Triplet excitons T1 are efficiently captured here, resulting in a significantly increased concentration, and undergo a TTF reaction to generate singlet excitons S1. The newly generated singlet excitons S1 transfer energy to the luminescent dopant BD in the adjacent third luminescent layer 130 via Förster energy transfer, causing it to emit light.

[0074] If the number of triplet excitons T1 is large (e.g., at high current densities), the second emitting layer 120 may become saturated, and the excess triplet excitons T1 can continue to migrate to the third emitting layer 130. Since the triplet energy level of the host material BH3 in the third emitting layer 130 is higher than that in the second emitting layer 120 but lower than that in the first emitting layer 110, after the triplet excitons T1 enter the third emitting layer 130, they can also continue to migrate to the adjacent fourth emitting layer 140 through Dexter energy transfer.

[0075] The fourth luminescent layer 140 is a pure host layer containing only the host material BH4. The triplet exciton T1 is captured again here, undergoing a TTF reaction to generate a singlet exciton S1, which transfers its energy to the luminescent dopant BD in the adjacent fifth luminescent layer 150. This process continues, forming a multi-level TTF reaction chain, achieving the step-by-step capture and efficient utilization of the triplet exciton T1.

[0076] In some embodiments, the multi-layered alternating structure has the following advantages:

[0077] First, multiple even-numbered layers containing only the host material form a multi-level energy potential well, which can more thoroughly collect triplet excitons T1, further increasing the total probability of the TTF reaction and obtaining a higher efficiency gain.

[0078] Second, the even-numbered layers containing only the host material provide an unobstructed channel for carrier transport, reducing the blocking effect of the luminescent dopant BD on carriers and helping to stably lock the carrier recombination region in the first luminescent layer 110.

[0079] Third, the multilayer thin-layer stacked structure can buffer the interface impact during long-term operation of the device, slow down interface degradation, and improve the long-term stability and lifespan of the device.

[0080] Figure 6 for Figure 5 The graph shows a comparison of the luminous efficiency of the OLED device in the illustrated embodiment with that of a traditional single-layer light-emitting layer structure. Curve D represents... Figure 5 The luminous efficiency of the embodiment shown is illustrated. Curve D represents the luminous efficiency of a traditional single-layer light-emitting layer structure. It can be seen that... Figure 3 The embodiment shown has a higher luminous efficiency than the traditional single-layer light-emitting layer structure at all current densities.

[0081] For example, the host material BH1 in the first luminescent sublayer 110 can be an anthracene derivative or a carbazole derivative. The host material BH2 in the second luminescent sublayer 120 can be a triazine or an anthracene derivative. The host material BH3 in the third luminescent sublayer 130 can be selected from materials that are the same as or similar to those in the first luminescent sublayer.

[0082] The luminescent dopant BD is a boron-nitrogen-based blue fluorescent material, a perylene-based blue fluorescent material, or a multiple resonance thermally activated delayed fluorescent material.

[0083] For example, the electron blocking layer 200 can be made of carbazole or aromatic amine hole transport material. When the host material BH1 in the first photonic layer 110 is an anthracene derivative or carbazole, the HOMO energy level difference between the two ranges from 0.2 eV to 0.4 eV.

[0084] In some embodiments of this invention, an electronic device is also provided, which includes the OLED device described above. Exemplary examples show that the electronic device can be any product or component with display functionality, such as electronic paper, OLED panels, mobile phones, tablets, televisions, monitors, laptops, digital photo frames, navigators, wearable devices, etc.

[0085] Since the electronic device in this embodiment uses the OLED device of the aforementioned embodiment, it also has the advantages of high luminous efficiency, long lifespan, and good efficiency stability.

[0086] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An OLED device, comprising an anode, a cathode, and a light-emitting layer disposed between the anode and the cathode, wherein the light-emitting layer comprises a host material and a light-emitting dopant, characterized in that, The light-emitting layer includes multiple light-emitting sub-layers, and the multiple light-emitting sub-layers include: The first photonic layer is configured as the main recombination region of electrons and holes for generating excitons, which include singlet excitons and triplet excitons; The second light-emitting sublayer is located on the side of the first light-emitting sublayer closer to the cathode and is disposed adjacent to the first light-emitting sublayer. The triplet energy level of the main material in the second light-emitting sublayer is lower than the triplet energy level of the main material in the first light-emitting sublayer, so that the triplet excitons generated in the first light-emitting sublayer migrate to the second light-emitting sublayer. The second luminescent layer is used to generate singlet excitons by causing triplet-triplet annihilation of the triplet excitons that migrate therein.

2. The OLED device according to claim 1, characterized in that, The plurality of light-emitting sublayers also include: The third light-emitting sublayer is located on the side of the second light-emitting sublayer closer to the cathode and is disposed adjacent to the second light-emitting sublayer. The triplet energy level of the main material in the third light-emitting sublayer is higher than the triplet energy level of the main material in the second light-emitting sublayer and lower than the triplet energy level of the main material in the first light-emitting sublayer.

3. The OLED device according to claim 2, characterized in that, The first, second, and third light-emitting sublayers each comprise a host material and a light-emitting dopant, wherein the triplet energy level of the light-emitting dopant is higher than that of the host material. The triplet energy level of the host material of the first luminescent sublayer is higher than that of the host material of the third luminescent sublayer. The triplet energy level of the host material of the third luminescent sublayer is higher than that of the host material of the second luminescent sublayer, and the triplet energy level difference of the host materials of adjacent luminescent sublayers is greater than 0.2 eV.

4. The OLED device according to claim 3, characterized in that, The singlet energy level of the luminescent dopant in the plurality of luminescent sublayers is lower than the singlet energy level of the host material in the luminescent sublayer, and the difference between the singlet energy level and the host material in the luminescent sublayer is greater than 0.2 eV.

5. The OLED device according to claim 2, characterized in that, The thickness of the first luminescent sublayer is 30 Å-70 Å; and / or, The thickness of the second luminescent sublayer is 10 Å-40 Å; and / or, The total thickness of the first light-emitting sublayer, the second light-emitting sublayer, and the third light-emitting sublayer is 150 Å-250 Å.

6. The OLED device according to claim 2, characterized in that, The plurality of light-emitting sublayers also include: The Nth luminescent sublayer, where N is a positive integer greater than 3, is located on the side of the third luminescent sublayer closer to the cathode. The Nth luminescent sublayer is adjacent to the (N-1)th luminescent sublayer, and the triplet energy level of the host material in the Nth luminescent sublayer is higher than the triplet energy level of the host material in the (N-1)th luminescent sublayer but lower than the triplet energy level of the host material in the first luminescent sublayer.

7. The OLED device according to claim 6, characterized in that, Among the plurality of light-emitting sublayers, starting from the first light-emitting sublayer, the odd-numbered light-emitting sublayers contain both a host material and a light-emitting dopant, while the even-numbered light-emitting sublayers contain only the host material.

8. The OLED device according to claim 7, characterized in that, The thickness of the even-numbered light-emitting sublayer is less than 30 Å.

9. The OLED device according to claim 7, characterized in that, The concentration of the light-emitting dopant in the first light-emitting sublayer is higher than the concentration of the light-emitting dopant in the other odd-numbered light-emitting sublayers.

10. The OLED device according to claim 9, characterized in that, The concentration of the luminescent dopant in the first luminescent sublayer is 1%-3%, and / or, The concentration of the light-emitting dopant in the odd-numbered light-emitting sublayers other than the first light-emitting sublayer is 0.5%-1.5%.

11. The OLED device according to claim 6, characterized in that, The triplet energy level of the host material in the odd-numbered light-emitting sublayer is not lower than the triplet energy level of the host material in the even-numbered light-emitting sublayer.

12. The OLED device according to claim 6, characterized in that, The triplet energy level of the host material in the first luminescent sublayer is higher than the triplet energy level of the host material in the other luminescent sublayers.

13. The OLED device according to claim 12, characterized in that, The energy difference between the triplet energy level of the host material in the first luminescent sublayer and the triplet energy level of the host material in the second luminescent sublayer is greater than 0.2 eV.

14. The OLED device according to claim 1, characterized in that, The triplet energy level of the luminescent dopant in the luminescent sublayer is higher than the triplet energy level of the host material in the luminescent sublayer, and the singlet energy level of the luminescent dopant in the luminescent sublayer is lower than the singlet energy level of the host material in the luminescent sublayer.

15. An electronic device, characterized in that, Includes the OLED device as described in any one of claims 1 to 14.

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