Organic electroluminescent display substrate and manufacturing method, display panel and display device

An organic electroluminescent display substrate is provided, which includes a base substrate, and a light-emitting unit and a light-sensing unit arranged on the base substrate, wherein the light-sensing unit is arranged on a light-emitting side of the light-emitting unit, and configured for sensing an intensity of light emitted from the light-emitting unit; a first planarization layer is arranged between the light-sensing unit and the light-emitting unit; the light-sensing unit comprises a first thin film transistor and a photosensitive sensor arranged sequentially in that order in a direction away from the base substrate, and a second planarization layer is arranged between the photosensitive sensor and the first thin film transistor. A display panel, a display device and a method for manufacturing the organic electroluminescent display substrate are further provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the U.S. national phase of PCT Application No. PCT/CN2020/128582 filed on Nov. 13, 2020, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the technical field of manufacturing display products, and more particularly to an organic electroluminescent display substrate, a manufacturing method, a display panel and a display device.

BACKGROUND

Organic Light-Emitting Diode (OLED) display products have been developed over a long period of time, have been developed rapidly in the recent years, and have gradually emerged in terminal products. There are still some technical problems in OLED displays, such as brightness compensation. The common compensation method is in electrical compensation, but due to the limited effect of the electrical compensation method, an optical compensation method is proposed. By adding a photosensitive sensor in the pixel, the intensity of OLED light emission is sensed, and the signal detected by the photosensitive sensor is fed back to the OLED pixel driving circuit, so as to realize corresponding compensation. In the process of realizing such an optical compensation method, after the photosensitive sensor process is completed, since it is necessary to ensure the quality of the film and ensure that the film is thick, the deposition time thereof usually takes 10-30 minutes, and the deposition gas is mainly SiH4 and H2, i.e. being in an environment of H, and under an H atmosphere for 10-30 minutes, the metal oxide semiconductor is easily conducted, which may adversely affect the device. A metal oxide semiconductor Thin Film Transistor (TFT) is substantially in a large current state, and is difficult to return to its original state in a subsequent process.

SUMMARY

In order to solve the above-mentioned technical problem, the present disclosure provides an organic electroluminescent display substrate, a manufacturing method, a display panel and a display device, to solve a problem of generating a dark current when a photosensitive sensor is used to sense an intensity of light emitted from a light-emitting unit.

In order to achieve the above object, embodiments of the present disclosure adopt the following technical solutions. An organic electroluminescent display substrate is provided, which includes a base substrate, a light-emitting unit and a light-sensing unit, wherein the light-emitting unit and the light-sensing unit are arranged on the base substrate, the light-sensing unit is arranged on a light-emitting side of the light-emitting unit, and configured for sensing an intensity of light emitted from the light-emitting unit;a first planarization layer is arranged between the light-sensing unit and the light-emitting unit;the light-sensing unit includes a first thin film transistor and a photosensitive sensor arranged sequentially in that order in a direction away from the base substrate, and a second planarization layer is arranged between the photosensitive sensor and the first thin film transistor.

Optionally, the photosensitive sensor includes a first electrode, a light sensitive layer and a second electrode arranged sequentially in that order in the direction away from the base substrate, the first electrode is connected to a first terminal of the first thin film transistor through a via hole penetrating through the second planarization layer, and the second electrode is electrically connected to an external circuit through a wire.

Optionally, a first passivation layer is arranged between the second planarization layer and the first thin film transistor, a second passivation layer is arranged between the second planarization layer and the photosensitive sensor, and via holes through which the first electrode passes to connect to the first thin film transistor are arranged respectively in the first passivation layer and the second passivation layer.

Optionally, an orthographic projection of the second planarization layer onto the base substrate covers an entirety of a display area of the base substrate.

Optionally, an area of an orthographic projection of the second planarization layer onto the base substrate is greater than or equal to an area of an orthographic projection of the photosensitive sensor onto the base substrate.

Optionally, an orthographic projection of the light-sensing unit onto the base substrate partially overlaps with an orthographic projection of the light-emitting unit on the base substrate.

Optionally, a third passivation layer is arranged between the light-sensing unit and the first planarization layer.

Optionally, the light-emitting unit includes a third electrode, a fourth electrode and a light-emitting functional layer arranged between the third electrode and the fourth electrode, and a pixel circuit layer is further arranged on the base substrate, and the pixel circuit layer includes a second thin film transistor configured for providing a driving signal to the light-emitting unit.

Optionally, the first thin film transistor and the second thin film transistor are arranged in a same layer.

Optionally, the organic electroluminescent display substrate further includes a color film layer arranged on the light-emitting side of the light-emitting unit.

Optionally, a light shielding layer is arranged between the base substrate and the pixel circuit layer.

Embodiments of the present disclosure further provide a display panel including the above-mentioned organic electroluminescent display substrate.

Embodiments of the present disclosure further provide a display device including the above-mentioned display substrate.

Embodiments of the present disclosure further provide a method for manufacturing the above-mentioned organic electroluminescent display substrate, including:forming the first thin film transistor on the base substrate;forming the second planarization layer on the first thin film transistor;forming the photosensitive sensor on the second planarization layer;forming the first planarization layer on the photosensitive sensor;forming the light-emitting unit on the first planarization layer.

Optionally, the method further includes: after forming the second planarization layer on the first thin film transistor,

forming a second passivation layer on the second planarization layer.

Advantageous effects of the present disclosure are as follows. A second planarization layer is arranged between the light-sensing unit and the first thin film transistor, to ensure that a bottom of the light-sensing unit is flat, which may facilitate to reduce the dark current of the light-sensing unit, ensure characteristics of the first thin film transistor, and suppress the occurrence of the case where the first thin film transistor generates a large current.

DETAILED DESCRIPTION

To further clarify the objects, technical solutions and advantages of the embodiments of the present disclosure, a more particular description of the technical solutions of the present disclosure will be rendered by reference to the drawings. Obviously, the embodiments described in the present disclosure are part, rather than all of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by a person of ordinary skill in the art are within the protection scope of the present disclosure.

In the description of the present disclosure, it should be understood that the orientation or positional relationship indicated by the terms “center”, “upper”, “lower”, “left”, “right”, “vertical”, “horizontal”, “inner”, “outer”, and the like is based on the orientation or positional relationship shown in the drawings, and is merely for convenience of describing the disclosure and simplifying the description, but not intended or implied that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present disclosure. In addition, the terms “first”, “second” and “third” are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Referring toFIGS.1and2, this embodiment provides an organic electroluminescent display substrate, comprising a base substrate10, and a light-emitting unit1and a light-sensing unit2arranged on the base substrate10, wherein the light-sensing unit2is arranged on a light-emitting side of the light-emitting unit1and configured for sensing an intensity of light emitted from the light-emitting unit1;a first planarization layer3is arranged between the light-sensing unit2and the light-emitting unit1;the light-sensing unit2comprises a first thin film transistor and a photosensitive sensor arranged sequentially in that order in a direction away from the base substrate10, and a second planarization layer4is arranged between the photosensitive sensor and the first thin film transistor.

A second planarization layer4is arranged between the photosensitive sensor and the first thin film transistor, and forms a double planarization layer structure with the first planarization layer3, so as to reduce the dark current of the light-sensing unit2, ensure the characteristics of the first thin film transistor, and suppress the occurrence of the case where the first thin film transistor generates a large current. By comparingFIG.3withFIG.5andFIG.6, the case where the first thin film transistor generates a large current is significantly suppressed after the second planarization layer is arranged in this embodiment.

In this embodiment, the second planarization layer4is a resin layer, but not limited thereto.

The resin layer contains at least one chemical organic substance, and achieves a hydrogen resistance effect through interaction or reaction between the organic substances, and the specific species of the substance can be selected according to actual needs as long as the second planarization layer reaches the conditions that the curing temperature is less than 260 degrees centigrade and the thermal decomposition temperature is greater than 450 degrees centigrade. For example, the organic substance can be a hydrogen resistance additive.

Illustratively in this embodiment, the photosensitive sensor comprises a first electrode21, a light sensitive layer22, and a second electrode23arranged sequentially in that order in a direction away from the base substrate10, the first electrode21is connected to a first terminal of the first thin film transistor through a via hole passing through the second planarization layer4, and the second electrode23is electrically connected to an external circuit through a wire.

Illustratively in this embodiment, the photosensitive sensor is a photodiode.

Illustratively in this embodiment, a first passivation layer7is arranged between the second planarization layer4and the first thin film transistor, a second passivation layer6is arranged between the second planarization layer4and the photosensitive sensor, and via holes through which the first electrode21passes to connect to the first thin film transistor are arranged respectively in the first passivation layer7and the second passivation layer6.

The first passivation layer7serves to isolate and protect the first thin film transistor, and the second passivation layer6is arranged so as to prevent the second planarization layer4from being etched due to over-etching in an etching process when the light-sensing unit2is formed.

In this embodiment, the second planarization layer4is arranged to reduce the dark current generated by the photosensitive sensor and to prevent the first thin film transistor from being adversely affected in an H environment during the manufacturing of the photosensitive sensor. Therefore, it is only necessary that the area of the second planarization layer4is not smaller than the area of the photosensitive sensor. Namely, the orthographic projection of the second planarization layer4onto the base substrate10is at least equal to the orthographic projection of the photosensitive sensor onto the base substrate10.

Illustratively in this embodiment, an orthographic projection of the second planarization layer4onto the base substrate10covers an entirety of the display area of the base substrate10, with reference toFIG.1. Illustratively in this embodiment, the second planarization layer is of an island structure arranged only below the photosensitive sensor, and the area of the orthographic projection of the second planarization layer4onto the base substrate10is greater than or equal to the area of the orthographic projection of the photosensitive sensor onto the base substrate10. When the area of the orthographic projection of the second planarization layer4onto the base substrate10is larger than the area of the orthographic projection of the photosensitive sensor onto the base substrate10, the difference between the area of the orthographic projection of the second planarization layer4onto the base substrate10and the area of the orthographic projection of the photosensitive sensor onto the base substrate10is less than a preset value (the preset value can be set according to practical requirements), with reference toFIGS.2and3.

It should be noted that both the arrangement of the second planarization layer shown inFIG.1and the arrangement of the second planarization layer shown inFIG.2can reduce the dark current of the light-sensing unit2, ensure the characteristics of the first thin film transistor, and prevent the first thin film transistor from generating a large current. However, it is preferable in this embodiment that the orthographic projection of the second planarization layer4onto the base substrate10covers the entirety of the display area of the base substrate10for the following reasons.

FIG.5is an IV schematic diagram of the first thin film transistor when the orthographic projection of the second planarization layer4onto the base substrate10covers the entirety of the display area of the base substrate10, andFIG.6is an IV schematic diagram of the first thin film transistor when the second planarization layer is of an island structure and is arranged only below the photosensitive sensor.FIG.7is an IV diagram showing a dark current generated by a light-sensing unit when an orthographic projection of the second planarization layer4onto the base substrate10covers an entirety of a display area of the base substrate10.

InFIGS.5and6, an ordinate indicates a current and an abscissa indicates a voltage, and for a thin film transistor in a normal state, a voltage is applied to the thin film transistor and the thin film transistor is turned on to generate a current, and as the voltage increases, the current gradually tends to be stabilized while no current is generated without applying the voltage. It can be seen fromFIGS.5and6that the orthographic projection of the second planarization layer4onto the base substrate10covers the entirety of the display area of the base substrate10, i.e. the second planarization layer integrally covers the entire base substrate, as shown inFIG.5(inFIG.5, the current curve corresponding to a negative voltage can be ignored since the current is very small). Therefore, the case where the first thin film transistor generates a large current is avoided. However, inFIG.6, although the case where the first thin film transistor generates a large current is suppressed as compared with the IV schematic diagram shown inFIG.4. However, since the first planarization layer is arranged only directly below the light-sensing unit, there is a portion of H entering the first thin film transistor below during the process of manufacturing the light-sensing unit, thereby adversely affects the characteristics of the first thin film transistor. Since the thin film transistor is caused to generate a current without applying a voltage, it is preferable in this embodiment that the orthographic projection of the second planarization layer4onto the base substrate10covers the entirety of the display area of the base substrate10.

It should be noted that the different curves inFIGS.4-6are different patterns obtained by testing at different locations on the base substrate.

FIG.7is a schematic diagram of a dark current generated by a photosensitive sensor when an orthographic projection of the second planarization layer4onto the base substrate10covers an entirety of a display area of the base substrate10. In general, when a voltage of −4v is provided, the dark current generated by the photosensitive sensor may be required to be less than 1.00E-9. It can be obtained fromFIG.7that when a voltage of −4v is supplied, as long as the dark current generated by the photosensitive sensor is less than 1.00E-13, 1.00E-14 can be achieved, the dark current generated by the photosensitive sensor can be reduced. A plurality of display panels are arranged on one glass substrate; the different curves inFIG.7are graphs obtained by testing the dark current of each of the photosensitive sensors on the plurality of display panels; and it can be obtained fromFIG.7that the arrangement of the second planarization layer improves the uniformity of the display panels.

Illustratively in this embodiment, the orthographic projection of the light-sensing unit2onto the base substrate10partially coincides with the orthographic projection of the light-emitting unit1onto the base substrate10.

The light-sensing unit2is located at the light-emitting side of the light-emitting unit1, and the light-sensing unit2partially overlaps the light-emitting unit1, that is, the orthographic projection of the light-sensing unit2onto the base substrate10partially coincides with the orthographic projection of the light-emitting unit1onto the base substrate10, so that part of the light emitted from the light-emitting unit1can be sensed by the light-sensing unit2.

Illustratively in this embodiment, a third passivation layer5is arranged between the light-sensing unit2and the first planarization layer3.

The third passivation layer5is formed on the photosensitive sensor to isolate and protect the photosensitive sensor.

Illustratively in this embodiment, the light-emitting unit1comprises a third electrode, a fourth electrode, and a light-emitting functional layer arranged between the third electrode and the fourth electrode, and a pixel circuit layer is further arranged on the base substrate10, and the pixel circuit layer comprises a second thin film transistor for providing a driving signal to the light-emitting unit1.

Illustratively in this embodiment, the first thin film transistor and the second thin film transistor are arranged in the same layer.

Illustratively in this embodiment, the organic electroluminescent display substrate further comprises a color filter9arranged on the light-emitting side of the light-emitting unit1.

The color filter9comprises a plurality of color resistance layers, and each of the light-emitting units1corresponds to a respective one of color resistance layers having a respective color, and R, namely, a red color resistance layer is represented inFIGS.1and2, and a green color resistance layer (G) or a blue color resistance layer (B) can alternatively be represented. After passing through the color filter9, the light emitted from the light-emitting unit achieves color display.

Illustratively in this embodiment, a light shielding layer20is arranged between the base substrate10and the pixel circuit layer.

The organic electroluminescent display substrate in this embodiment is a bottom-emitting display device, and the light-shielding layer20is arranged on the base substrate10to prevent ambient light from adversely affecting the second thin film transistor.

Illustratively in this embodiment, the light shielding layer20is a metal layer, the second thin film transistor comprises a second active layer103, a second gate insulation layer102and a second gate electrode101, a buffer layer8is arranged between the light shielding layer20and the second active layer103, and the light shielding layer20is connected to the second gate electrode101of the second thin film transistor to constitute a double-gate structure. The top-gate structure is susceptible to substrate glass impurities, but the double-gate TFT can ensure that the characteristics of the gate electrode in the second thin film transistor are not adversely affected, thereby ensuring the stability of the TFT.

Embodiments of the present disclosure further provide a display device comprising the organic electroluminescent display substrate described above.

Embodiments of the present disclosure provide a method for manufacturing the organic electroluminescent display substrate described above, comprising the following steps:forming a first thin film transistor on the base substrate10, and forming an active layer (first active layer203), a gate insulation layer (first gate insulation layer202), a gate electrode (first gate electrode201) and a source-drain pattern (source electrode205and drain electrode204) on the base substrate10sequentially in that order;forming a second planarization layer4on the first thin film transistor;forming a photosensitive sensor on the second planarization layer4, and forming a first electrode21, a light sensitive layer22and a second electrode23on the second planarization layer4sequentially in that order;forming a first planarization layer3on the photosensitive sensor; andforming a light-emitting unit1on the first planarization layer3.

Illustratively in this embodiment, the method further comprises: after forming the second planarization layer4on the first thin film transistor,

forming a second passivation layer6on the second planarization layer4.

It should be appreciated that the above-described embodiments are merely illustrative embodiments that have been employed to illustrate the principles of the present disclosure, and that the present disclosure is not limited thereto. A person of ordinary skill in the art understands that various modifications and improvements can be made without departing from the spirit and scope of the present disclosure.