Display substrate, display apparatus, and method of fabricating display substrate

1. A display substrate, comprising a plurality of light emitting elements respectively in a plurality of subpixels configured to emit light for image display;

wherein a respective one of the plurality of subpixels comprises:

a base substrate;

a first auxiliary cathode on the base substrate;

a passivation layer on a side of the first auxiliary cathode away from the base substrate;

a first insulating layer on a side of the passivation layer away from the base substrate;

a second auxiliary cathode on a side of the first insulating layer away from the base substrate;

a second insulating layer on a side of the second auxiliary cathode away from the base substrate; and

a pixel definition layer on a side of the second insulating layer away from the base substrate;

wherein the display substrate has a cathode aperture extending through the pixel definition layer and an auxiliary cathode aperture extending through the first insulating layer and the passivation layer;

a cathode of a respective one of the plurality of light emitting elements extends into the cathode aperture to electrically connect with the second auxiliary cathode; and

the second auxiliary cathode extends into the auxiliary cathode aperture to electrically connect with the first auxiliary cathode;

wherein the display substrate further comprises a plurality of low voltage signal lines respectively extending into the plurality of subpixels; and

wherein a respective one of the plurality of low voltage signal lines is electrically connected to the first auxiliary cathode.

2. The display substrate of claim 1 , wherein the cathode of a respective one of the plurality of light emitting elements is substantially outside the auxiliary cathode aperture; and

the second insulating layer is substantially inside the auxiliary cathode aperture.

3. The display substrate of claim 1 , wherein an orthographic projection of the second auxiliary cathode on the base substrate substantially covers an orthographic projection of the second insulating layer on the base substrate; and

the second auxiliary cathode and the second insulating layer together form a substantially flat surface.

4. The display substrate of claim 3 , wherein the cathode of the respective one of the plurality of light emitting elements is in direct contact with the second auxiliary cathode and is in direct contact with the second insulating layer; and

a portion of the cathode of the respective one of the plurality of light emitting elements is on the substantially flat surface.

5. The display substrate of claim 4 , wherein a direct contacting interface between the cathode of the respective one of the plurality of light emitting elements and the second auxiliary cathode substantially surrounds a direct contacting interface between the cathode of the respective one of the plurality of light emitting elements and the second insulating layer.

6. The display substrate of claim 3 , wherein the respective one of the plurality of subpixels further comprises a third auxiliary cathode on a side of the second auxiliary cathode and the second insulating layer away from the base substrate;

wherein the second insulating layer is sandwiched between the second auxiliary cathode and third auxiliary cathode;

the cathode of the respective one of the plurality of light emitting elements extends into the cathode aperture to electrically connect with the second auxiliary cathode through the third auxiliary cathode; and

the third auxiliary cathode is on the substantially flat surface.

7. The display substrate of claim 6 , wherein the cathode of the respective one of the plurality of light emitting elements is in direct contact with the third auxiliary cathode; and

the second auxiliary cathode and the second insulating layer are spaced apart from the cathode of the respective one of the plurality of light emitting elements by the third auxiliary cathode.

8. The display substrate of claim 6 , wherein the third auxiliary cathode is in direct contact with the second auxiliary cathode and is in direct contact with the second insulating layer.

9. The display substrate of claim 8 , wherein a direct contacting interface between the third auxiliary cathode and the second auxiliary cathode substantially surrounds a direct contacting interface between the third auxiliary cathode and the second insulating layer.

10. The display substrate of claim 6 , wherein the second auxiliary cathode, the third auxiliary cathode, and the cathode of the respective one of the plurality of light emitting elements are made of a substantially transparent conductive material; and

the first auxiliary cathode is made of a metallic conductive material.

11. The display substrate of claim 1 , wherein the second auxiliary cathode and the cathode of the respective one of the plurality of light emitting elements are made of a substantially transparent conductive material; and

the first auxiliary cathode is made of a metallic conductive material.

12. The display substrate of claim 1 , wherein the respective one of the plurality of subpixels further comprises a thin film transistor;

wherein the thin film transistor comprises a source electrode and a drain electrode;

the drain electrode of the thin film transistor is electrically connected to an anode of the respective one of the plurality of light emitting elements; and

the first auxiliary cathode is in a same layer and comprises a same material as the source electrode and the drain electrode of the thin film transistor.

13. The display substrate of claim 1 , wherein the first insulating layer and the second insulating layer are made of organic insulating materials.

14. A display substrate, comprising a plurality of light emitting elements respectively in a plurality of subpixels configured to emit light for image display;

wherein a respective one of the plurality of subpixels comprises:

a base substrate;

a first auxiliary cathode on the base substrate;

a passivation layer on a side of the first auxiliary cathode away from the base substrate;

a first insulating layer on a side of the passivation layer away from the base substrate;

a second auxiliary cathode on a side of the first insulating layer away from the base substrate;

a second insulating layer on a side of the second auxiliary cathode away from the base substrate; and

a pixel definition layer on a side of the second insulating layer away from the base substrate;

wherein the display substrate has a cathode aperture extending through the pixel definition layer and an auxiliary cathode aperture extending through the first insulating layer and the passivation layer;

a cathode of a respective one of the plurality of light emitting elements extends into the cathode aperture to electrically connect with the second auxiliary cathode; and

the second auxiliary cathode extends into the auxiliary cathode aperture to electrically connect with the first auxiliary cathode;

wherein the first insulating layer is made of a positive photoresist material the second insulating layer is made of a negative photoresist material; or

the first insulating layer is made of a negative photoresist material, and the second insulating layer is made of a positive photoresist material.

15. A display apparatus, comprising the display substrate of claim 1 , and one or more integrated circuits connected to the display substrate.

16. A method of fabricating a display substrate comprising a plurality of light emitting elements respectively in a plurality of subpixels configured to emit light for image display;

wherein forming a respective one of the plurality of subpixels comprises:

forming a first auxiliary cathode on a base substrate;

forming a passivation layer on a side of the first auxiliary cathode away from the base substrate;

forming a first insulating layer on a side of the passivation layer away from the base substrate;

forming a second auxiliary cathode on a side of the first insulating layer away from the base substrate;

forming a second insulating layer on a side of the second auxiliary cathode away from the base substrate; and

forming a pixel definition layer on a side of the second insulating layer away from the base substrate;

wherein the display substrate has a cathode aperture extending through the pixel definition layer and an auxiliary cathode aperture extending through the first insulating layer and the passivation layer;

a cathode of a respective one of the plurality of light emitting elements extends into the cathode aperture to electrically connect with the second auxiliary cathode; and

the second auxiliary cathode extends into the auxiliary cathode aperture to electrically connect with the first auxiliary cathode;

wherein forming the first insulating layer comprises:

forming a first photoresist layer on a side of the passivation layer away from the base substrate; and

exposing the first photoresist layer using a first mask plate and developing the first photoresist layer to form the auxiliary cathode aperture, thereby forming the first insulating layer, the auxiliary cathode aperture extending through the first insulating layer and the passivation layer and exposing a surface of the first auxiliary cathode;

wherein forming the second insulating layer comprises:

forming a second photoresist layer on a side of the first insulating layer and the second auxiliary cathode away from the base substrate; and

exposing the second photoresist layer using a second mask plate and developing the second photoresist layer to form the second insulating layer, wherein the second insulating layer is substantially inside the auxiliary cathode aperture;

wherein the second mask plate is the same as the first mask plate;

wherein the first photoresist layer is made of a positive photoresist material the second photoresist layer is made of a negative photoresist material, or the first photoresist layer is made of a negative photoresist material the second photoresist layer is made of a positive photoresist material.

17. The method of claim 16 , subsequent to forming the second insulating layer, further comprising forming the cathode of the respective one of the plurality of light emitting elements;

wherein the cathode of the respective one of the plurality of light emitting elements is in direct contact with the second auxiliary cathode and is in direct contact with the second insulating layer.

18. The method of claim 17 , subsequent to forming the second insulating layer and prior to forming the cathode of the respective one of the plurality of light emitting elements, further comprising forming a third auxiliary cathode on a side of the second auxiliary cathode and the second insulating layer away from the base substrate;

wherein the second insulating layer is sandwiched between the second auxiliary cathode and third auxiliary cathode; and

the cathode of the respective one of the plurality of light emitting elements extends into the cathode aperture to electrically connect with the second auxiliary cathode through the third auxiliary cathode.