Quantum dot light emitting devices

1. A quantum dot light emitting diode comprising i) an emitting layer of at least one semiconductor nanoparticle made from semiconductor materials selected from the group consisting of Group II-VI compounds, Group II-V compounds, Group III-VI compounds, Group III-V compounds, Group IV-VI compounds, Group I-III-VI compounds, Group II-IV-VI compounds, Group II-IV-V compounds, or any combination thereof; and ii) a polymer for hole injection or hole transport layer, comprising one or more triaryl aminium radical cations having the structure (S1)

and additionally comprising one or more triaryl amine structures (S2)

wherein each of R 11 , R 12 , R 13 , R 14 , R 15 , R 21 , R 22 , R 23 , R 24 , R 25 , R 31 , R 32 , R 33 , R 34 , and R 35 is independently selected from the group consisting of hydrogen, deuterium, halogens, amine groups, hydroxyl groups, sulfonate groups, nitro groups, and organic groups, wherein two or more of R 11 , R 12 , R 13 , R 14 , R 15 , R 21 , R 22 , R 23 , R 24 , R 25 , R 31 , R 32 , R 33 , R 34 , and R 35 are optionally connected to each other to form a ring structure;

wherein one or more of R 11 , R 12 , R 13 , R 14 , R 15 , R 21 , R 22 , R 23 , R 24 , R 25 , R 31 , R 32 , R 33 , R 34 , and R 35 is covalently bound to the polymer, and

wherein A − is an anion;

and wherein the diode comprises a gradient layer that is located between the anode layer and the emitting layer and that comprises S1 groups and S2 groups, wherein the mole ratio of S2 groups to S1 groups is not uniform throughout the gradient layer.

2. The diode of claim 1 , wherein the diode comprises a dual-functional layer that functions as a hole injection layer and a hole transport layer, and wherein the diode does not comprise any additional hole injection layer or hole transport layer, and wherein the dual-functional layer comprises polymer that comprises one or more triaryl aminium radical cations having the structure (S1).

3. The diode of claim 2 , wherein the diode additionally comprises one or more electron blocking layers.

4. The diode of claim 1 , wherein the polymer is a vinyl polymer or a conjugated polymer.

5. The diode of claim 1 , wherein the mole ratio of structures S2 to structures S1 is from 999:1 to 0.001:1.

6. The diode of claim 1 , wherein the mole ratio of S2 groups to S1 groups in the portion of the gradient layer nearest the anode layer is defined as MRA:1, wherein the mole ratio of S2 groups to S1 groups in the portion of the gradient layer nearest the emitting layer is defined as MRE:1, and wherein MRA is less than MRE.

7. The diode of claim 6 , wherein the ratio of MRA to MRE is 0.9:1 or less.

8. The diode of claim 1 , wherein the composition additionally comprises one or more polymers that have no structure S1.

9. The diode of claim 1 , wherein the polymer has number average molecular weight of 2,500 to 300,000 Da.

10. The diode of claim 1 , wherein A − is selected from the group consisting of BF 4 − , PF 6 − , SbF 6 − , AsF 6 − , ClO 4 − , anions of structure SA, anions of structure MA, and mixtures thereof, wherein the structure SA is

wherein Q is B, Al, or Ga, and wherein each of y1, y2, y3, and y4 is independently 0 to 5, and wherein each R 61 group, each R 62 group, each R 63 group, and each R 641 group is selected independently from the group consisting of deuterium, a halogen, an alkyl, and a halogen-substituted alkyl, and wherein any two groups selected from the R 61 groups, the R 62 groups, the R 63 groups, and the R 641 groups are optionally bonded together to form a ring structure, and wherein the structure MA is

wherein M is B, Al, or Ga, and wherein each of R 62 , R 63 , R 64 , and R 65 is independently alkyl, aryl, fluoroaryl, or fluoroalkyl.