Display panel, display device and preparation method of display panel

Abstract

The embodiment of the invention provides a display panel, a display device and a preparation method of the display panel, and the display panel comprises a substrate which is provided with a first side; the light-emitting unit is arranged on the first side, and the light-emitting unit comprises a first hole transport layer; the photoelectric sensing unit is arranged on the first side, the photoelectric sensing unit is configured to receive an optical signal and generate a corresponding electric signal according to the optical signal, the photoelectric sensing unit comprises a second hole transport layer, a photoelectric conversion layer and a buffer layer, and the buffer layer is arranged on the side, facing the second hole transport layer, of the photoelectric conversion layer; wherein the first hole transport layer and the second hole transport layer are made of the same material, the buffer layer has first conductivity, the second hole transport layer has second conductivity, and the first conductivity is greater than the second conductivity. According to the embodiment of the invention, by adding the buffer layer, the performance of the photoelectric detector of the display panel can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of display devices, and in particular to a display panel, a display device, and a method for manufacturing a display panel. Background Art

[0002] Biometrics plays an important role in smartphones and tablets. The common existing technologies include facial recognition and fingerprint recognition, among which fingerprint recognition includes ultrasonic fingerprint, capacitive fingerprint and optical fingerprint. Among them, optical fingerprint has the advantages of high resolution, high sensitivity and can be used for life and health detection. Summary of the invention

[0003] The embodiments of the present application provide a display panel, a display device, and a method for manufacturing a display panel, aiming to improve the performance of a photodetector in a display panel.

[0004] An embodiment of the first aspect of the present application provides a display panel, comprising: a substrate having a first side; a light-emitting unit arranged on the first side, the light-emitting unit comprising a first hole transport layer; a photoelectric sensing unit arranged on the first side, the photoelectric sensing unit being configured to receive a light signal and generate a corresponding electrical signal according to the light signal, the photoelectric sensing unit comprising a second hole transport layer, a photoelectric conversion layer and a buffer layer, the buffer layer being arranged on a side of the photoelectric conversion layer facing the second hole transport layer; wherein the first hole transport layer and the second hole transport layer are made of the same material, the buffer layer has a first conductivity, the second hole transport layer has a second conductivity, and the first conductivity is greater than the second conductivity.

[0005] According to an implementation scheme of the first aspect of the present application, the buffer layer and the photoelectric conversion layer are arranged adjacent to each other; or, the photoelectric sensing unit further includes a third hole transport layer, which is arranged on a side of the buffer layer away from the second hole transport layer, and the photoelectric conversion layer is arranged on a side of the third hole transport layer away from the buffer layer.

[0006] According to any of the aforementioned embodiments of the first aspect of the present application, the photoelectric sensing unit includes a third hole transport layer, and the third hole transport layer has a first thickness, and the first thickness is no greater than 50 nanometers.

[0007] According to any of the aforementioned embodiments of the first aspect of the present application, the first thickness is not greater than 50 nanometers, and the first thickness is not less than 3 nanometers.

[0008] According to any of the aforementioned embodiments of the first aspect of the present application, the first hole transport layer and the second hole transport layer are an integrated structure.

[0009] According to any of the aforementioned embodiments of the first aspect of the present application, the material of the buffer layer includes a first buffer material, wherein:

[0010] The first buffer material is an organic P-type dopant; and / or,

[0011] The first buffer material is an inorganic P-type dopant; and / or,

[0012] The first buffer material is a metallic material.

[0013] According to any of the foregoing embodiments of the first aspect of the present application, the first buffer material is an organic P-type dopant, and the LUMO energy level of the buffer layer is not greater than -4.0 electron volts.

[0014] According to any of the foregoing embodiments of the first aspect of the present application, the organic P-type dopant includes at least one of NDP-9, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane.

[0015] According to any of the foregoing embodiments of the first aspect of the present application, the first buffer material is an inorganic P-type dopant, and the conduction energy level of the buffer layer is not greater than -4.5 electron volts.

[0016] According to any of the foregoing embodiments of the first aspect of the present application, the inorganic P-type dopant includes at least one of molybdenum trioxide, vanadium pentoxide, and tungsten trioxide.

[0017] According to any of the foregoing embodiments of the first aspect of the present application, the first buffer material is a metallic material, and the work function of the buffer layer is higher than 4.0 electron volts.

[0018] According to any of the foregoing embodiments of the first aspect of the present application, the first buffer material is a metallic material, and the metallic material includes at least one of silver, gold, aluminum, copper, and chromium.

[0019] According to any of the foregoing embodiments of the first aspect of the present application, the material of the buffer layer is the first buffer material, and the buffer layer has a second thickness that is not less than 0.1 nanometer and not greater than 20 nanometers.

[0020] According to any of the foregoing embodiments of the first aspect of the present application, the buffer layer further includes a first host material doped with the first buffer material, the second hole transport layer includes a second host material, and the first host material and the second host material are the same.

[0021] According to any of the foregoing embodiments of the first aspect of the present application, the first host material includes at least one of 4,4'-cyclohexylene[N,N-bis(4-methylphenyl)aniline], tris(4-carbazol-9-ylphenyl)amine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, and 4,4',4''-tris[2-naphthylphenylamino]triphenylamine.

[0022] According to any of the foregoing embodiments of the first aspect of the present application, the buffer layer has a third thickness, the third thickness is not less than 0.1 nanometers and not more than 50 nanometers.

[0023] According to any of the foregoing embodiments of the first aspect of the present application, the first buffer material has a first amount of substance, the material of the buffer layer has a second amount of substance, and the ratio of the first amount of substance to the second amount of substance is not less than 0.01% and not more than 50%.

[0024] According to any of the foregoing embodiments of the first aspect of the present application, the buffer layer has a first hole carrier concentration, the second hole transport layer has a second hole carrier concentration, and the first hole carrier concentration is greater than the second hole carrier concentration.

[0025] According to any of the foregoing embodiments of the first aspect of the present application, the buffer layer is a single-layer structure, or the buffer layer includes two or more sub-layers.

[0026] According to any of the foregoing embodiments of the first aspect of the present application, the materials of the two or more sub-layers are the same or different.

[0027] According to any of the foregoing embodiments of the first aspect of the present application, the orthographic projection of the photo-electric conversion layer on the substrate is located within the orthographic projection of the buffer layer on the substrate;

[0028] Preferably, the orthographic projections of the first hole transport layer and the second hole transport layer on the substrate overlap with the orthographic projection of the buffer layer on the substrate.

[0029] According to any of the foregoing embodiments of the first aspect of the present application, the photo-electric conversion layer includes a donor material and an acceptor material.

[0030] According to any of the foregoing embodiments of the first aspect of the present application, the photo-electric conversion layer includes a mixed layer, and the mixed layer includes a donor material and an acceptor material.

[0031] According to any of the foregoing embodiments of the first aspect of the present application, the photo-electric conversion layer further includes a donor layer, the donor layer is located on the side of the mixed layer facing the substrate, and the donor layer includes a donor material; and / or, the photo-electric conversion layer further includes an acceptor layer, the acceptor layer is located on the side of the mixed layer facing away from the substrate, and the acceptor layer includes an acceptor material.

[0032] According to any of the foregoing embodiments of the first aspect of the present application, the light-emitting unit further includes a first hole injection layer, the first hole injection layer is disposed on the side of the first hole transport layer facing the substrate, and the photo-electric sensing unit further includes a second hole injection layer, the second hole injection layer is disposed on the side of the second hole transport layer facing the substrate.

[0033] According to any of the foregoing embodiments of the first aspect of the present application, the materials of the first hole injection layer and the second hole injection layer are the same.

[0034] According to any of the foregoing embodiments of the first aspect of the present application, the first hole injection layer and the second hole injection layer are of an integral structure.

[0035] According to any of the foregoing embodiments of the first aspect of the present application, the light-emitting unit further includes a first electron transport layer disposed on a side of the first hole transport layer away from the substrate, and the photoelectric sensing unit further includes a second electron transport layer disposed on a side of the photoelectric conversion layer away from the second hole transport layer.

[0036] According to any of the foregoing embodiments of the first aspect of the present application, the light-emitting unit further includes a first hole blocking layer disposed on a side of the first electron transport layer facing the substrate, and the photoelectric sensing unit further includes a second hole blocking layer located on a side of the second electron transport layer facing the photoelectric conversion layer.

[0037] An embodiment of the second aspect of the present application further provides a display device, including the display panel provided in any of the foregoing embodiments of the first aspect.

[0038] An embodiment of the third aspect of the present application further provides a method for manufacturing a display panel, including:

[0039] Preparing a first hole transport layer of the light-emitting unit and a second hole transport layer of the photoelectric sensing unit on a first side of the substrate, wherein the photoelectric sensing unit is configured to receive an optical signal and generate a corresponding electrical signal according to the optical signal, and the materials of the first hole transport layer and the second hole transport layer are the same;

[0040] Preparing a buffer layer on a side of the second hole transport layer away from the substrate, wherein the buffer layer has a first conductivity and the second hole transport layer has a second conductivity, and the first conductivity is greater than the second conductivity.

[0041] According to the embodiment of the third aspect of the present application, after the step of preparing the buffer layer on a side of the second hole transport layer away from the substrate, it further includes:

[0042] Preparing a photoelectric conversion layer on a side of the buffer layer away from the second hole transport layer; or,

[0043] Preparing a third hole transport layer on a side of the buffer layer away from the second hole transport layer and preparing a photoelectric conversion layer on a side of the third hole transport layer away from the buffer layer.

[0044] According to any of the foregoing embodiments of the third aspect of the present application, the first hole transport layer and the second hole transport layer are formed in the same process step.

[0045] According to any of the foregoing embodiments of the third aspect of the present application, the buffer layer and the photoelectric conversion layer are prepared using the same precision mask.

[0046] In the display panel provided by the embodiment of the present application, the display panel includes a substrate, a light-emitting unit, and a photoelectric sensing unit. The light-emitting unit is used to realize the light-emitting display of the display panel, and the photoelectric sensing unit is used to realize the photoelectric detection function of the display panel. The materials of the first hole transport layer of the light-emitting unit and the second hole transport layer of the photoelectric sensing unit are the same, so that the first hole transport layer and the second hole transport layer can be formed in the same process step, which can simplify the manufacturing process of the display panel. A buffer layer is provided between the photoelectric conversion layer and the second hole transport layer of the photoelectric sensing unit, and the conductivity of the buffer layer is greater than that of the second hole transport layer. The potential barrier between the buffer layer and the photoelectric conversion layer is small, which can reduce the potential barrier between the second hole transport layer and the photoelectric conversion layer, improve the extraction efficiency of photo-generated holes, and further improve the performance of the light sensing unit. Therefore, by adding a buffer layer between the photoelectric conversion layer and the second hole transport layer in the embodiment of the present application, the performance of the photodetector of the display panel can be improved. Description of the Drawings

[0047] By reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present application will become more apparent, wherein the same or similar reference numerals denote the same or similar features.

[0048] Figure 1 is a schematic structural diagram of a display panel provided by a related embodiment;

[0049] Figure 2 is a schematic layer structure diagram of a display panel provided by a related embodiment.

[0050] Figure 3 is a schematic energy level structure diagram of a display panel provided by a related embodiment;

[0051] Figure 4 is a schematic layer structure diagram of a display panel provided by an embodiment of the present application;

[0052] Figure 5 is a schematic energy level structure diagram of a display panel provided by an embodiment of the present application;

[0053] Figure 6 is a schematic layer structure diagram of a display panel provided by another embodiment of the present application;

[0054] Figure 7 is a schematic energy level structure diagram of a display panel provided by another embodiment of the present application;

[0055] Figure 8 is a schematic layer structure diagram of a display panel provided by still another embodiment of the present application;

[0056] Figure 9It is a schematic diagram of the layer structure of a display panel provided by another embodiment of the present application;

[0057] Figure 10 It is a test curve graph of a display panel provided by an embodiment of the present application;

[0058] Figure 11 It is a schematic diagram of the preparation process of a display panel provided by an embodiment of the present application.

[0059] Description of reference numerals:

[0060] 100, substrate; 110, first electrode; 120, second electrode;

[0061] 210, hole transport layer; 211, first sub-layer; 212, second sub-layer; 220, hole blocking layer; 230, hole injection layer; 240, electron transport layer;

[0062] 310, light-emitting structure; 320, photoinductive structure; 321, mixed layer; 322, donor layer; 323, acceptor layer;

[0063] 400, buffer layer. Detailed implementation manners

[0064] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In the following detailed description, many specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application. In the drawings and the following description, at least some of the well-known structures and technologies are not shown in order to avoid unnecessarily obscuring the present application; and, for clarity, the dimensions of some structures may be exaggerated. In addition, the features, structures, or characteristics described below may be combined in any suitable manner in one or more embodiments.

[0065] In the description of the present application, it should be noted that unless otherwise specified, the meaning of "a plurality" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0066] The orientation terms used in the following description are all the directions shown in the figures, and do not limit the specific structure of the embodiments of the present application. In the description of the present application, it should also be noted that unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0067] Biometric identification plays an important role in mobile terminals such as smart phones and tablets. In the prior art, the common methods include face recognition and fingerprint recognition. Among them, fingerprint recognition includes ultrasonic fingerprint, capacitive fingerprint, and optical fingerprint, etc. Optical fingerprint has become the mainstream technical means because of its advantages such as high resolution, high sensitivity, and the ability to perform life and health detection.

[0068] Figure 1 A display panel provided by a related technology Figure 1 The light transmission path is schematically shown by an arrow. It should be noted that integrating an organic light-emitting diode and a photoelectric sensor together in the panel can achieve a larger integration area and a thinner overall thickness of the machine. The organic photodetector (OPD) prepared based on organic photosensitive materials is compatible with the vacuum evaporation process of the organic light-emitting diode (Organic Light Emitting Diode, OLED), and is an important direction for integrating fingerprint recognition functions in the panel in the future.

[0069] As Figure 2 shown, an OPD generally includes a cathode, an anode, a photoinductive structure (Activelayer, or also called a photosensitive layer), and a carrier layer. It is an optoelectronic device that converts an incident optical signal into an electrical signal, while an organic light-emitting diode is a device that converts an electrical signal into an optical signal.

[0070] The optoelectronic induction structure in OPD usually includes two organic materials with staggered energy levels. One of the materials is a donor material, and typical donor materials include copper phthalocyanine oligomers (chemical symbol: CuPc), dibutyl phthalate (abbreviation: DBP), etc. The other material is an acceptor material, and typical acceptor materials include fullerenes (such as C60 and C70. Among them, C60 is a molecule composed of 60 carbon atoms, C60 is also called buckminsterfullerene, and C70 is a molecule composed of 70 carbon atoms). The working principle of OPD can include the following steps, namely: the material absorbs light to generate excitons, the excitons diffuse to the donor-acceptor interface, the excitons diffuse to the donor-acceptor interface and charge separation occurs, and then charge transport and collection. In order to improve the exciton dissociation efficiency, the donor and acceptor are usually mixed (co-evaporated) together as the optoelectronic induction structure.

[0071] To improve the carrier collection efficiency, a reverse bias voltage, such as -3V, is usually applied to the cathode and anode of the OPD. However, this reverse voltage will also increase the injection of dark current.

[0072] OPD is usually configured to achieve optoelectronic sensing functions. For example, OPD can be used for image recognition. Further, when OPD is configured to achieve fingerprint recognition, it is required that OPD has a high recognition accuracy. Therefore, it is required that OPD has a high signal-to-noise ratio (Signal to Interference plus Noise Ratio, SNR). It should be noted that in OPD, the size of the signal-to-noise ratio is related to the external quantum efficiency (External quantum efficiency; EQE). Specifically, EQE represents the ratio of the number of photo-generated electrons flowing through the device under illumination to the number of photons incident on the device, that is, the ability to convert light into electricity. EQE is the most basic parameter of OPD. Therefore, maximizing EQE is the direction for optimizing OPD devices and improving product performance.

[0073] In the integrated application of OPD and OLED, such as Figure 3As shown, considering the cost and process difficulty, OPD needs to share some carrier layers with OLED. Although this integration method is very economical, it also reduces the device performance of OPD. And both OPD and OLED will include a thicker hole transport layer (HTL). This thick hole transport layer can effectively block the anode electron injection during reverse bias and reduce the dark current. However, since the hole transport layer is very thick and has a large resistance, further, the HOMO (Highest Occupied Molecular Orbital) energy level of the hole transport layer does not match the HOMO energy level of the donor in the photoelectric sensing structure (that is, there is a certain potential barrier). Therefore, the extraction of photogenerated holes will be hindered. Therefore, the EQE of the OPD device with a thick hole transport layer will be very low.

[0074] In order to solve the above technical problems, in the embodiment of the present application, an interface modification film layer is introduced into the OPD device structure in the integrated application of OPD and OLED to solve the problem of hindered extraction of photogenerated holes and improve the EQE of the OPD device.

[0075] In order to better understand this application, Figures 4 to 10 The display panel and the display device according to the embodiments of the present application are described in detail.

[0076] Please also read Figure 4 and Figure 5 , Figure 4 is a schematic diagram of a layer structure of a display panel provided in an embodiment of the present application; Figure 5 It is a schematic diagram of an energy level structure of a display panel provided in an embodiment of the present application.

[0077] like Figure 4 and Figure 5 As shown, the display panel provided by the embodiment of the first aspect of the present application includes: a substrate 100, having a first side; a light-emitting unit, arranged on the first side, the light-emitting unit includes a first hole transport layer 211; a photoelectric sensing unit, arranged on the first side, the photoelectric sensing unit is configured to receive a light signal and generate a corresponding electrical signal according to the light signal, the photoelectric sensing unit includes a second hole transport layer 212, a photoelectric conversion layer 320 and a buffer layer 400, the buffer layer 400 is arranged on the side of the photoelectric conversion layer 320 facing the second hole transport layer 212; wherein the first hole transport layer 211 and the second hole transport layer 212 are made of the same material, the buffer layer 400 has a first electrical conductivity, the second hole transport layer 212 has a second electrical conductivity, and the first electrical conductivity is greater than the second electrical conductivity.

[0078] Optionally, the light-emitting unit includes a light-emitting layer 310 , and the light-emitting layer 310 is located on a side of the first hole transport layer 211 facing away from the substrate 100 .

[0079] In the display panel provided in the embodiment of the present application, the display panel includes a substrate 100, a light-emitting unit, and a photoelectric sensing unit. The light-emitting unit is used to realize the light-emitting display of the display panel, and the photoelectric sensing unit is used to realize the photoelectric detection function of the display panel. The materials of the first hole transport layer 211 of the light-emitting unit and the second hole transport layer 212 of the photoelectric sensing unit are the same, so that the first hole transport layer 211 and the second hole transport layer 212 can be formed in the same process step, which can simplify the manufacturing process of the display panel. A buffer layer 400 is provided between the photoelectric conversion layer 320 and the second hole transport layer 212 of the photoelectric sensing unit, and the conductivity of the buffer layer 400 is greater than that of the second hole transport layer 212. The potential barrier between the buffer layer 400 and the photoelectric conversion layer 320 is small, which can reduce the potential barrier between the second hole transport layer 212 and the photoelectric conversion layer 320, improve the extraction efficiency of photo-generated holes, and thus improve the performance of the light sensing unit. Therefore, by adding the buffer layer 400 between the photoelectric conversion layer 320 and the second hole transport layer 212 in the embodiment of the present application, the performance of the photodetector of the display panel can be improved.

[0080] Optionally, the first hole transport layer 211 and the second hole transport layer 212 are integrally provided as a hole transport layer 210. That is, the first hole transport layer 211 and the second hole transport layer 212 are two parts at different positions on the same film layer. The first hole transport layer 211 is the part of the hole transport layer 210 stacked with the light-emitting layer 310, and the second hole transport layer 212 is the part of the hole transport layer 210 stacked with the photoelectric conversion layer 320. Optionally, in some other embodiments, there may also be a gap between the first hole transport layer 211 and the second hole transport layer 212.

[0081] Optionally, the light-emitting unit is a structure for converting an electrical signal into an optical signal to realize the light-emitting display of the display panel. Optionally, the photoelectric sensing unit is a structure for converting an optical signal line into an electrical signal to realize the photoelectric detection function of the display panel. Optionally, the photoelectric sensing unit is the above-mentioned OPD device.

[0082] Optionally, the display panel further includes a first electrode 110 and a second electrode 120. The first electrode 110 and the second electrode 120 are respectively disposed on both sides of the light-emitting unit and the photoelectric sensing unit. The light-emitting unit can be driven to emit light through the first electrode 110 and the second electrode 120, and the signal of the photoelectric sensing unit can also be transmitted through the first electrode 110 and the second electrode 120. Optionally, the substrate 100 further includes a driving circuit for driving the light-emitting unit to emit light.

[0083] Optionally, one of the first electrode 110 and the second electrode 120 is an anode, and the other is a cathode. In the embodiments of the present application, the first electrode 110 is taken as an example of the anode, and the second electrode 120 is taken as an example of the cathode. The material of the first electrode 110 may include indium tin oxide, and the material of the second electrode 120 may include magnesium (chemical symbol: Mg), silver (chemical symbol: Ag), ytterbium (chemical symbol: Yb), etc.

[0084] There are various ways to arrange the position of the buffer layer 400. For example, the buffer layer 400 may be directly located between the second hole transport layer 212 and the photoelectric conversion layer 320, that is, the buffer layer 400 and the photoelectric conversion layer 320 are arranged in contact. The shortest distance d between the buffer layer 400 and the photoelectric conversion layer 320 is 0. In this embodiment, since the conductivity of the buffer layer 400 is greater than that of the second hole transport layer 212, the conductivity of the buffer layer 400 is greater than that of the hole transport layer 210. Therefore, the problem that the extraction of photo-generated holes is hindered due to the large resistance of the too thick hole transport layer 210 is solved.

[0085] In addition, since the conductivity of the buffer layer 400 is greater than that of the second hole transport layer 212, the potential barrier between the buffer layer 400 and the photoelectric conversion layer 320 is smaller, and the problem that the extraction of photo-generated holes is hindered due to a certain potential barrier between the hole transport layer 210 and the photoelectric conversion layer 320 can be better improved.

[0086] Or, in some other embodiments, as Figure 6 and Figure 7 shown, the hole transport layer 210 includes a third hole transport layer 213, that is, the photoelectric sensing unit further includes a third hole transport layer 213. The third hole transport layer 213 is disposed on a side of the buffer layer 400 away from the second hole transport layer 212, and the photoelectric conversion layer 320 is disposed on a side of the third hole transport layer 213 away from the buffer layer 400.

[0087] In these embodiments, the second hole transport layer 212 and the third hole transport layer 213 are respectively disposed on both sides of the buffer layer 400. That is, since the third hole transport layer 213 is provided between the optoelectronic conversion layer 320 and the buffer layer 400, the shortest distance d between the buffer layer 400 and the optoelectronic conversion layer 320 is not 0. By adding the buffer layer 400 between the second hole transport layer 212 and the third hole transport layer 213, the conductivity of the overall second hole transport layer 212 and third hole transport layer 213 can be improved. This can not only solve the problem that the extraction of photo-generated holes is hindered due to the large resistance of the overly thick hole transport layer 210, but also reduce the potential barrier between the hole transport layer 210 and the optoelectronic conversion layer 320, and improve the problem that the extraction of photo-generated holes is hindered due to a certain potential barrier between the hole transport layer 210 and the optoelectronic conversion layer 320.

[0088] In any of the above embodiments, when the optoelectronic sensing unit includes the third hole transport layer 213, the third hole transport layer 213 has a first thickness, where the first thickness is not greater than 50 nanometers. It should be noted that the first thickness is not greater than 50 nanometers, that is, the shortest distance d between the buffer layer 400 and the optoelectronic conversion layer 320 is less than or equal to 50 nanometers. Such a thickness setting can ensure that the third hole transport layer 213 has an appropriate thickness, and further ensure an appropriate distance between the buffer layer 400 and the optoelectronic conversion layer 320, thereby effectively improving the potential barrier existing between the hole transport layer 210 and the optoelectronic conversion layer 320.

[0089] Optionally, when the optoelectronic sensing unit includes the third hole transport layer 213, the third hole transport layer 213 has a first thickness, where the first thickness is not greater than 50 nanometers and not less than 3 nanometers. It should be noted that when the first thickness is within the above range, it can not only improve the problem that the blocking effect on electrons is too small due to the too small first thickness, but also improve the problem that the hole extraction is blocked and the EQE is reduced due to the too large first thickness.

[0090] In some alternative embodiments, the display panel further includes a hole injection layer 230, and the hole injection layer 230 is disposed on the side of the hole transport layer 210 facing the substrate 100. The hole injection layer 230 includes a first hole injection layer 231 and a second hole injection layer 232. For example, the light-emitting unit includes the first hole injection layer 231, and the optoelectronic sensing unit includes the second hole injection layer 232. The first hole injection layer 231 is disposed on the side of the first hole transport layer 211 facing the substrate 100, and the second hole injection layer 232 is disposed on the side of the second hole transport layer 212 facing the substrate 100.

[0091] Optionally, the buffer layer 400 and the hole injection layer 230 are spaced apart. For example, the buffer layer 400 and the second hole injection layer 232 are spaced apart.

[0092] In these embodiments, the second hole injection layer 232 and the buffer layer 400 are spaced apart, and a hole transport layer 210 (e.g., the second hole transport layer 212) may be provided between the second hole injection layer 232 and the buffer layer 400 to improve the hole transport efficiency.

[0093] Optionally, the materials of the first hole injection layer 231 and the second hole injection layer 232 may be the same. That is, the first hole injection layer 231 and the second hole injection layer 232 can be formed in the same process step, which can simplify the manufacturing process of the display panel.

[0094] Optionally, the first hole injection layer 231 and the second hole injection layer 232 are of an integral structure. For example, the first hole injection layer 231 and the second hole injection layer 232 are different regions on the same hole injection layer 230. Optionally, in some other embodiments, there may also be a gap between the first hole injection layer 231 and the second hole injection layer 232.

[0095] Optionally, the display panel may further include a hole blocking layer 220 and an electron transport layer 240.

[0096] Optionally, the light-emitting unit further includes a first electron transport layer 241, which is disposed on the side of the first hole transport layer 211 away from the substrate 100. The photoelectric sensing unit further includes a second electron transport layer 242, which is disposed on the side of the photoelectric conversion layer 320 away from the second hole transport layer 212. Optionally, the electron transport layer 240 includes the above-mentioned first electron transport layer 241 and the above-mentioned second electron transport layer 242. That is, the first electron transport layer 241 and the second electron transport layer 242 may be integrally provided, or the first electron transport layer 241 and the second electron transport layer 242 may have a gap.

[0097] Optionally, the hole blocking layer 220 includes a first hole blocking layer 221 and a second hole blocking layer 222. The first hole blocking layer 221 and the first hole transport layer 211 are stacked, and the second hole blocking layer 222 and the second hole transport layer 212 are stacked. Optionally, the light-emitting unit further includes the above-mentioned first hole blocking layer 221, and the first hole blocking layer 221 is disposed on the side of the first electron transport layer 241 facing the substrate 100. The photoelectric sensing unit further includes the above-mentioned second hole blocking layer 222, and the second hole blocking layer 222 is located on the side of the second electron transport layer 242 facing the substrate 100. Optionally, the first hole blocking layer 221 and the second hole blocking layer 222 may be an integral structure, or the first hole blocking layer 221 and the second hole blocking layer 222 may have a gap.

[0098] There are various ways to set the material of the buffer layer 400, and the material of the buffer layer 400 and the material of the second hole injection layer 252 may be the same.

[0099] In some alternative embodiments, the material of the buffer layer 400 includes a first buffer material, and the first buffer material is an organic P-type dopant, and / or the first buffer material is an inorganic P-type dopant; and / or the first buffer material is a metal material. By making the buffer layer 400 include an organic P-type dopant, an inorganic P-type dopant or a metal material, the conductivity of the buffer layer 400 can be increased, so that the conductivity of the buffer layer 400 is greater than the conductivity of the second hole transport layer 212, thereby solving the problem that the extraction of photo-generated holes is hindered due to the large resistance of the too-thick hole transport layer 210. At the same time, the problem of a certain potential barrier between the second hole transport layer 212 and the photoelectric conversion layer 320 is also improved.

[0100] Optionally, when the first buffer material is an organic P-type dopant, the LUMO (Lowest Unoccupied Molecular Orbital) energy level of the buffer layer 400 is not greater than -4.0 electron volts.

[0101] When the first buffer material is an organic P-type dopant, the first buffer material may include at least one of NDP-9, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane (abbreviation: F4-TCNQ).

[0102] When the first buffer material is an inorganic P-type dopant, the inorganic P-type dopant includes at least one of molybdenum trioxide (chemical symbol: MoO3), vanadium pentoxide (chemical symbol: V2O5), and tungsten trioxide (chemical symbol: WO3).

[0103] Optionally, when the first buffer material is an inorganic P-type dopant, the conduction energy level of the buffer layer 400 is not greater than -4.5 electron volts.

[0104] Optionally, the material of the buffer layer 400 can be formed by mixing other materials and the first buffer material. Alternatively, the material of the buffer layer 400 is the first buffer material, that is, the buffer layer 400 does not include other materials. When the material of the buffer layer 400 is the first buffer material, for example, when the material of the buffer layer 400 is the above-mentioned organic P-type dopant or the above-mentioned inorganic P-type dopant, the buffer layer 400 has a second thickness, the second thickness is not less than 0.1 nanometer and not greater than 20 nanometers. This can avoid the problem that the conductivity of the buffer layer 400 is insufficient due to being too thin, which hinders the extraction of photo-generated holes, and at the same time, it can also avoid the problem of lateral crosstalk caused by lateral leakage generated by the buffer layer 400 being too thick.

[0105] In some other alternative embodiments, the first buffer material can be a metal material, and the work function of the first buffer material is higher than 4.0 electron volts. The first buffer material is a high work function material, which can improve the conductivity of the first buffer material, and then improve the conductivity of the entire buffer layer 400, so as to solve the problem that the extraction of photo-generated holes is hindered due to the large resistance of the too thick hole transport layer 210. At the same time, it can also better improve the problem that the extraction of photo-generated holes is hindered due to a certain potential barrier between the hole transport layer 210 and the photoelectric conversion layer 320.

[0106] When the first buffer material is a metal material, the first buffer material can include at least one of silver (chemical symbol: Ag), gold (chemical symbol: Au), aluminum (chemical symbol: Al), copper (chemical symbol: Cu), and chromium (chemical symbol: Cr), so that the first buffer material has good conductivity.

[0107] As above, the material of the buffer layer 400 can be the first buffer material, that is, the material of the buffer layer 400 is a single-layer organic P-type dopant and / or a single-layer inorganic P-type dopant and / or a single-layer metal material. For example, the buffer layer 400 is a silver metal layer, etc.

[0108] In some other alternative embodiments, the material of the buffer layer 400 further includes a first host material, and the buffer layer 400 is obtained by doping the first buffer material in the first host material.

[0109] In these alternative embodiments, the material of the buffer layer 400 includes the first host material doped with the first buffer material. The first host material and the first buffer material are mixed, and the conductivity of the buffer layer 400 can be adjusted to a suitable range.

[0110] Optionally, the hole transport layer 210 includes a second host material, and the first host material and the second host material may be the same, so as to simplify the manufacturing process of the display panel.

[0111] Optionally, the first host material may include at least one of 4,4'-cyclohexylene[N,N-bis(4-methylphenyl)aniline] (abbreviated as: TAPC), tris(4-carbazol-9-ylphenyl)amine (abbreviated as: TCTA), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (abbreviated as: NPB), 4,4',4''-tris[2-naphthylphenylamino]triphenylamine (abbreviated as: 2-TNATA). By selecting a suitable first host material and a suitable mixing ratio, the conductivity of the buffer layer 400 can be adjusted to a suitable range.

[0112] Optionally, when the material of the buffer layer 400 includes a first host material and a first buffer material, the buffer layer 400 has a third thickness, the third thickness is not less than 0.1 nanometer and not more than 50 nanometers, so as to avoid the problem that the extraction of photo-generated holes is hindered due to insufficient conductivity of the too thin buffer layer 400. At the same time, it can also avoid the problem of lateral crosstalk caused by lateral leakage of the too thick buffer layer 400.

[0113] Optionally, the first buffer material has a first amount of substance, the material of the buffer layer has a second amount of substance, and the ratio of the first amount of substance to the second amount of substance is not less than 0.01% and not more than 50%. This makes the mixture of the first buffer material and the first host material more uniform, with a larger contact area, and can better improve the conductivity of the buffer layer 400.

[0114] In some alternative embodiments, the buffer layer 400 has a first hole carrier concentration, the second hole transport layer 212 has a second hole carrier concentration, and the first hole carrier concentration is greater than the second hole carrier concentration. During the use of the display panel, the hole carrier concentration in the buffer layer 400 is greater than the hole carrier concentration in the second hole transport layer 212, making the potential barrier between the buffer layer 400 and the photoelectric conversion layer 320 smaller.

[0115] The buffer layer 400 may be a single-layer structure, that is, the buffer layer 400 is formed by using the same material in the same process step.

[0116] Alternatively, the buffer layer 400 includes more than two sublayers, and the more than two sublayers of the buffer layer 400 can be prepared and formed in different process steps. The materials of the more than two sublayers can be the same or different. By adjusting the materials of different sublayers, the potential barrier between the buffer layer 400 and the hole transport layer 210 can be reduced, and the potential barrier between the buffer layer 400 and the photoelectric conversion layer 320 can be reduced.

[0117] Optionally, the orthographic projection of the photoelectric conversion layer 320 on the substrate 100 is located within the orthographic projection of the buffer layer 400 on the substrate 100, so that the buffer layer 400 can be correspondingly arranged at different positions of the photoelectric conversion layer 320, thereby better improving the problem of a large potential barrier between the photoelectric conversion layer 320 and the hole transport layer 210.

[0118] Optionally, the photoelectric conversion layer 320 and the buffer layer 400 can be arranged in one-to-one correspondence, that is, the orthographic projection of each photoelectric conversion layer 320 on the substrate 100 is located within the orthographic projection of each buffer layer 400 on the substrate 100, so as to improve the problem of large potential barriers between each photoelectric conversion layer 320 and the hole transport layer 210.

[0119] Or, if Figure 8 and Figure 9 As shown, in some embodiments, the buffer layer 400 may be a common layer, specifically, the orthographic projections of the first hole transport layer 211 and the second hole transport layer 212 on the substrate 100 overlap with the orthographic projections of the buffer layer 400 on the substrate 100. For example, the first hole transport layer 211 and the second hole transport layer 212 are integrated into the hole transport layer 210, and the buffer layer 400 may be prepared and formed using the same mask plate as the hole transport layer 210 to simplify the preparation process of the display panel.

[0120] In some optional embodiments, the photoelectric conversion layer 320 includes a donor material and an acceptor material, and the donor material and the acceptor material interact with each other to realize a photoelectric sensing function.

[0121] Optionally, the photoelectric conversion layer 320 includes a mixed layer 321 , and the material of the mixed layer 321 includes a donor material and an acceptor material to reduce the potential barrier between the photoelectric conversion layer 320 and other layer structures.

[0122] Optionally, the photoelectric conversion layer 320 further includes a donor layer 322, which is located on the side of the mixed layer 321 facing the substrate 100, and the material of the donor layer 322 includes a donor material; and / or, the photoelectric conversion layer 320 further includes an acceptor layer 323, which is located on the side of the mixed layer 321 facing away from the substrate 100, and the material of the acceptor layer 323 includes an acceptor material.

[0123] To further illustrate the beneficial effects of this application, please refer to Figure 10, the inventor conducted comparative experiments. The comparative examples include: Comparative Example 1 and Example 1. Both Comparative Example 1 and Example 1 provide a display panel including a light-emitting unit and a photoelectric sensing unit.

[0124] The difference between Example 1 and Comparative Example 1 is that a buffer layer 400 is introduced between the photoelectric conversion layer 320 and the second hole transport layer 212 in the photoelectric sensing unit. The thickness of the third hole transport layer 213 between the buffer layer 400 and the photoelectric sensing unit is 20 nanometers, the thickness of the buffer layer 400 is 5 nanometers, and the material of the buffer layer 400 is the same as that of the hole injection layer 230.

[0125] By testing the above Comparative Example 1 and Example 1 when the wavelength of the incident light is 590 nanometers, the Figure 10 shown curve graph is obtained. Figure 10 Among them, the abscissa is the reverse voltage applied to the OPD. It can be Figure 10 clearly seen that when the buffer layer 400 is not provided, the EQE of Comparative Example 1 is very low. After introducing the buffer layer 400, the EQE of the display panel is significantly increased by 25%. It shows that the setting of the buffer layer 400 can not only solve the problem that the extraction of photo-generated holes is hindered due to the large resistance of the too thick hole transport layer 210, but also significantly reduce the interface barrier between the hole transport layer 210 and the photoelectric conversion layer 320.

[0126] An embodiment of the second aspect of the present application further provides a display device, including the display panel of any of the above first aspect embodiments. Since the display device provided by the embodiment of the second aspect of the present application includes the display panel of any of the above first aspect embodiments, the display device provided by the embodiment of the second aspect of the present application has the beneficial effects of the display panel of any of the above first aspect embodiments, which will not be elaborated here.

[0127] The display device in the embodiments of the present application includes, but is not limited to, devices with display functions such as mobile phones, personal digital assistants (Personal Digital Assistant, abbreviated as: PDA), tablet computers, e-books, televisions, access control systems, smart landline telephones, consoles, etc.

[0128] An embodiment of the third aspect of the present application further provides a method for manufacturing a display panel. The display panel can be the display panel provided by any of the above first aspect embodiments. Please refer to Figures 1 to 11 together, the method for manufacturing a display panel may include:

[0129] Step S01: Prepare a first hole transport layer 211 of a light-emitting unit and a second hole transport layer 212 of a photoelectric sensing unit on a first side of a substrate 100. The photoelectric sensing unit is configured to receive an optical signal and generate a corresponding electrical signal according to the optical signal. The first hole transport layer 211 and the second hole transport layer 212 are made of the same material.

[0130] Step S02: Prepare a buffer layer 400 on a side of the second hole transport layer 212 facing away from the substrate. The buffer layer 400 has a first conductivity, and the second hole transport layer 212 has a second conductivity, and the first conductivity is greater than the second conductivity.

[0131] Optionally, the method may further include:

[0132] Step S03: Prepare a light-emitting layer 310 on one side of the first hole transport layer 211. A plurality of light-emitting layers 310 are arranged in an array on the first hole transport layer 211.

[0133] Step S04: Prepare a photoelectric conversion layer 320 on a side of the buffer layer 400 facing away from the second hole transport layer 212. The photoelectric conversion layer 320 and the light-emitting layer 310 are arranged at intervals, or prepare a third hole transport layer 213 on a side of the buffer layer 400 facing away from the second hole transport layer 212, and prepare a photoelectric conversion layer 320 on a side of the third hole transport layer 213 facing away from the buffer layer 400.

[0134] Step S05: Prepare a first hole blocking layer 221 and a second hole blocking layer 222 on sides of the light-emitting layer 310 and the photoelectric conversion layer 320 facing away from the substrate 100 to form a display panel.

[0135] Optionally, the order of step S02 and step S03 may be that step S02 is performed before or after step S03. Optionally, when step S03 is performed after step S02, step S03 and step S04 may be formed in the same process step to simplify the preparation process of the display panel.

[0136] In the display panel prepared by using the method provided in the embodiments of the present application, the display panel includes a substrate 100, a light-emitting unit, and a photoelectric sensing unit. The light-emitting unit is used to realize the light-emitting display of the display panel, and the photoelectric sensing unit is used to realize the photoelectric detection function of the display panel. The materials of the first hole transport layer 211 of the light-emitting unit and the second hole transport layer 212 of the photoelectric sensing unit are the same, so that the first hole transport layer 211 and the second hole transport layer 212 can be formed in the same process step, which can simplify the manufacturing process of the display panel. A buffer layer 400 is disposed between the photoelectric conversion layer 320 and the second hole transport layer 212 of the photoelectric sensing unit, and the conductivity of the buffer layer 400 is greater than that of the second hole transport layer 212. The potential barrier between the buffer layer 400 and the photoelectric conversion layer 320 is small. This can not only solve the problem that the extraction of photo-generated holes is hindered due to the large resistance of the overly thick hole transport layer 210, but also reduce the potential barrier between the second hole transport layer 212 and the photoelectric conversion layer 320, further improving the extraction efficiency of photo-generated holes, and thus improving the performance of the photoelectric sensing unit. Therefore, by adding the buffer layer 400 between the photoelectric conversion layer 320 and the second hole transport layer 212, the embodiments of the present application can improve the photoelectric detection performance of the display panel.

[0137] Optionally, the buffer layer 400 and the photoelectric conversion layer are adjacent to each other, and the orthographic projection of the photoelectric conversion layer 320 on the substrate 100 overlaps with the orthographic projection of the buffer layer 400 on the substrate 100. In steps S02 and S04, the buffer layer 400 and the photoelectric conversion layer 320 can be prepared by using the same precision mask plate to simplify the manufacturing process of the display panel.

[0138] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the present application, and components therein can be replaced with equivalents. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A display panel, characterized in that, Comprising: A substrate having a first side; A light-emitting unit disposed on the first side, the light-emitting unit including a first hole transport layer; A photoelectric sensing unit disposed on the first side, the photoelectric sensing unit being configured to receive an optical signal and generate a corresponding electrical signal according to the optical signal, the photoelectric sensing unit including a second hole transport layer, a photoelectric conversion layer, and a buffer layer, the buffer layer being disposed on a side of the photoelectric conversion layer facing the second hole transport layer; Wherein, the materials of the first hole transport layer and the second hole transport layer are the same, the buffer layer has a first conductivity, the second hole transport layer has a second conductivity, and the first conductivity is greater than the second conductivity.

2. The display panel according to claim 1, wherein The buffer layer and the photoelectric conversion layer are adjacent to each other; or, The photoelectric sensing unit further includes a third hole transport layer, the third hole transport layer being disposed on a side of the buffer layer facing away from the second hole transport layer, and the photoelectric conversion layer being disposed on a side of the third hole transport layer facing away from the buffer layer; Preferably, the photoelectric sensing unit includes the third hole transport layer, the third hole transport layer having a first thickness, and the first thickness is not greater than 50 nanometers; Preferably, the first thickness is not greater than 50 nanometers and the first thickness is not less than 3 nanometers; Preferably, the first hole transport layer and the second hole transport layer are of an integral structure.

3. The display panel according to claim 1, wherein The material of the buffer layer includes a first buffer material, wherein: The first buffer material is an organic P-type dopant; and / or, The first buffer material is an inorganic P-type dopant; and / or, The first buffer material is a metal material; Preferably, the first buffer material is the organic P-type dopant, and the LUMO energy level of the buffer layer is not greater than -4.0 electron volts; Preferably, the organic P-type dopant includes at least one of NDP-9, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane; Preferably, the first buffer material is the inorganic P-type dopant, and the conductive energy level of the buffer layer is not greater than -4.5 electron volts; Preferably, the inorganic P-type dopant includes at least one of molybdenum trioxide, vanadium pentoxide, and tungsten trioxide; Preferably, the first buffer material is the metal material, and the work function of the buffer layer is higher than 4.0 electron volts; Preferably, the first buffer material is the metal material, and the metal material includes at least one of silver, gold, aluminum, copper, and chromium.

4. The display panel according to claim 3, wherein The material of the buffer layer is the first buffer material, the buffer layer having a second thickness, and the second thickness is not less than 0.1 nanometers and not greater than 20 nanometers.

5. The display panel according to claim 3, characterized in that The buffer layer further includes a first host material doped with the first buffer material, the second hole transport layer includes a second host material, and the first host material and the second host material are the same; Preferably, the first host material includes at least one of 4,4'-cyclohexene [N,N-bis(4-methylphenyl)aniline], tri(4-carbazole-9-phenyl)amine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, and 4,4',4"-tris[2-naphthylphenylamino]triphenylamine; Preferably, the buffer layer has a third thickness, the third thickness is not less than 0.1 nanometers, and the third thickness is not greater than 50 nanometers; Preferably, the first buffer material has an amount of a first substance, the material of the buffer layer has an amount of a second substance, the ratio of the amount of the first substance to the amount of the second substance is not less than 0.01%, and the ratio of the amount of the first substance to the amount of the second substance is not greater than 50%.

6. The display panel according to claim 1, wherein, The buffer layer has a first hole carrier concentration, the second hole transport layer has a second hole carrier concentration, and the first hole carrier concentration is greater than the second hole carrier concentration.

7. The display panel according to claim 1, wherein The buffer layer is a single-layer structure, or the buffer layer includes more than two sub-layers; Preferably, the materials of the two or more sub-layers are the same or different.

8. The display panel according to claim 1, wherein The orthographic projection of the photoelectric conversion layer on the substrate is located within the orthographic projection of the buffer layer on the substrate; Preferably, the orthographic projections of the first hole transport layer and the second hole transport layer on the substrate overlap with the orthographic projection of the buffer layer on the substrate.

9. The display panel according to claim 1, wherein The photoelectric conversion layer includes a donor material and an acceptor material; Preferably, the photoelectric conversion layer comprises a mixed layer, and the mixed layer comprises the donor material and the acceptor material; Preferably, the photoelectric conversion layer further includes a donor layer, which is located on the side of the mixed layer facing the substrate, and the donor layer includes the donor material; and / or, the photoelectric conversion layer further includes an acceptor layer, which is located on the side of the mixed layer facing away from the substrate, and the acceptor layer includes the acceptor material.

10. The display panel according to claim 1, wherein The light-emitting unit further includes a first hole injection layer, which is disposed on a side of the first hole transport layer facing the substrate, and the photoelectric sensing unit further includes a second hole injection layer, which is disposed on a side of the second hole transport layer facing the substrate; Preferably, the first hole injection layer and the second hole injection layer are made of the same material; Preferably, the first hole injection layer and the second hole injection layer are an integrated structure; Preferably, the light-emitting unit further includes a first electron transport layer, which is disposed on a side of the first hole transport layer away from the substrate, and the photoelectric sensor unit further includes a second electron transport layer, which is disposed on a side of the photoelectric conversion layer away from the second hole transport layer; Preferably, the light-emitting unit further includes a first hole blocking layer, which is arranged on a side of the first electron transport layer facing the substrate, and the photoelectric sensing unit further includes a second hole blocking layer, which is located on a side of the second electron transport layer facing the photoelectric conversion layer.

11. A display device, characterized in that, Comprising a display panel according to any one of claims 1-10.

12. A method for preparing a display panel, characterized in that, Comprising: Preparing a first hole transport layer of a light-emitting unit and a second hole transport layer of a photoelectric sensing unit on a first side of a substrate, wherein the photoelectric sensing unit is configured to receive an optical signal and generate a corresponding electrical signal according to the optical signal, and the materials of the first hole transport layer and the second hole transport layer are the same; Preparing a buffer layer on a side of the second hole transport layer facing away from the substrate, wherein the buffer layer has a first conductivity, the second hole transport layer has a second conductivity, and the first conductivity is greater than the second conductivity.

13. The preparation method according to claim 12, characterized in that, After the step of preparing the buffer layer on the side of the second hole transport layer facing away from the substrate, further comprising: Preparing a photoelectric conversion layer on a side of the buffer layer facing away from the second hole transport layer; or, Preparing a third hole transport layer on a side of the buffer layer facing away from the second hole transport layer and preparing a photoelectric conversion layer on a side of the third hole transport layer facing away from the buffer layer; Preferably, the first hole transport layer and the second hole transport layer are formed in the same process step; Preferably, the buffer layer and the photoelectric conversion layer are prepared using the same precision mask.

Images