Shaped nanocrystal particles and methods for working the same

1. A nanocrystal particle made by a process comprising:

(a) providing a core having a first crystal structure in a solution; and

(b) forming an arm extending from the core having a second crystal structure in the solution.

2. A photovoltaic device comprising the nanocrystal particle of claim 1 .

3. A nanocrystal particle made by a process comprising:

introducing semiconductor nanocrystal particle precursors into a heated mixture of surfactants capable of promoting the growth of tetrapod shaped semiconductor nanocrystal particles; and

forming the tetrapod shaped semiconductor nanocrystal particle.

4. A nanocrystal particle comprising:

a core having a first crystal structure; and

at least an arm extending from the core having a second crystal structure.

5. The nanocrystal particle of claim 4 wherein the arm is a first arm, and wherein the nanocrystal particle further comprises:

at least a second arm extending from the core, the second arm having the second crystal structure.

6. The nanocrystal particle of claim 4 wherein the arm is a first arm, and wherein the nanocrystal particle further comprises:

at least a second arm extending from the core, the second arm having the second crystal structure; and

at least a third arm extending from the core, the third arm having the second crystal structure.

7. The nanocrystal particle of claim 4 wherein the arm is a first arm, and wherein the nanocrystal particle further comprises:

at least a second arm extending from the core, the second arm having the second crystal structure;

at least a third arm extending from the core, the third arm having the second crystal structure; and

at least a fourth arm extending from the core, the fourth arm having the second crystal structure.

8. The nanocrystal particle of claim 4 further comprising amphiphilic molecules bound to the surfaces of the arm.

9. The nanocrystal particle of claim 4 further comprising second, third, and fourth arms extending from the core, wherein the nanocrystal particle is a tetrapod shaped nanocrystal particle.

10. The nanocrystal particle of claim 4 wherein the core and the arm comprise a compound semiconductor.

11. The nanocrystal particle of claim 4 wherein the core is a first core, and wherein the arm is a first arm that has a proximate end proximate the first core and a distal end distal to the first core, and wherein the particle further comprises:

a second core at the distal end of the first arm and additional arms extending from the second core.

12. The nanocrystal particle of claim 4 wherein the first crystal structure is a zinc-blende crystal structure, and the second crystal structure is a wurtzite crystal structure.

13. The nanocrystal particle of claim 4 wherein the core has a diameter from about 3 to about 4 nanometers and the arm has a length of from about 4 to about. 100 nanometers.

14. The nanocrystal particle of claim 4 wherein the core and the arm comprise CdTe.

15. A photovoltaic device comprising the nanocrystal particle of claim 4 .

16. A branched nanocrystal particle comprising:

a core;

at least a first arm extending from the core; and

at least a second arm extending from the core, wherein the second arm forms a branch with respect to the first arm, and

wherein the core, the first arm, and the second arm comprise a Group II-VI or a Group III-V semiconductor.

17. The branched nanocrystal particle of claim 16 further comprising:

a third arm extending from the core, and a fourth arm extending from the core, wherein the first, second, third, and fourth arms, and the core form a tetrapod.

18. The branched nanocrystal particle of claim 16 wherein the core is a first core, and wherein the first arm includes a proximate end proximate to the first core and a distal end distal to the first core, and wherein the branched nanocrystal particle further comprises:

a second core at the distal end of the first nanocrystal particle; and

additional arms extending from the second core.

19. The branched nanocrystal particle of claim 16 further comprising a surfactant molecule attached to the core, the first arm, or the second arm.

20. The branched nanocrystal particle of claim 16 wherein the core has a diameter of about 3 nm to about 4 nm, and wherein each of the first and second arms have a length from about 4 nm to about 100 nm.

21. The branched nanocrystal particle of claim 16 wherein the Group II-VI or Group III-V semiconductor comprises CdSe or CdTe.

22. The branched nanocrystal particle of claim 16 wherein the core has a first crystal structure and wherein the first and second arms have a second crystal structure.

23. The branched nanocrystal particle of claim 16 wherein the core has a zinc blende crystal structure and wherein the first and second arms have a wurtzite crystal structure.

24. A tetrapod shaped nanocrystal particle comprising:

a core having a first crystal structure;

a first arm extending from the core;

a second arm extending from the core;

a third arm extending from the core; and

a fourth arm extending from the core, wherein the first, second, third, and fourth arms have a second crystal structure,

wherein the first crystal structure is different than the second crystal structure.

25. The tetrapod shaped nanocrystal particle of claim 24 wherein the tetrapod shaped nanocrystal comprises a compound semiconductor.

26. The tetrapod shaped nanocrystal particle of claim 24 wherein the tetrapod shaped nanocrystal comprises a compound semiconductor selected from the group consisting of CdTe and CdSe.

27. The tetrapod shaped nanocrystal particle of claim 24 wherein the core has a diameter from about 3 to about 4 nanometers and wherein the first, second, third, and fourth arms each have a length of from about 4 to about 100 nanometers.

28. The tetrapod shaped nanocrystal particle of claim 24 wherein first crystal structure is a cubic crystal structure and the second crystal structure is a hexagonal crystal structure.

29. The tetrapod shaped nanocrystal particle of claim 24 .wherein first crystal structure is a zinc blende crystal structure and the second crystal structure is a wurtzite crystal structure.

30. The tetrapod shaped nanocrystal particle of claim 24 wherein first crystal structure is a zinc blende crystal structure and the second crystal structure is a wurtzite crystal structure.

31. The tetrapod shaped nanocrystal particle of claim 24 comprising a metal.

32. The tetrapod shaped nanocrystal particle of claim 24 further comprising a surfactant molecule bound to at least one of the first, second, third, or fourth arms.

33. The tetrapod shaped nanocrystal particle of claim 24 wherein each of the first, second, third, and fourth arms has an aspect ratio greater than about 1.0.

34. The tetrapod shaped nanocrystal particle of claim 24 wherein the first, second, third, and fourth arms each have substantially the same length.

35. A photovoltaic device comprising:

the tetrapod shaped nanocrystal particle of claim 24 .

36. A nanocrystal particle in the form a teardrop or an arrow.

37. The nanocrystal particle of claim 36 wherein the nanocrystal particle comprises CdTe or CdSe.

38. The nanocrystal particle of claim 36 wherein the nanocrystal particle comprises a Group III-V or a Group II-VI semiconductor.