Nanocrystal and photovoltaic device comprising the same

Abstract

A nanocrystal with high light absorption efficiency and a broad absorption spectrum, and a photovoltaic device comprising the nanocrystal are disclosed. The nanocrystal of the present invention comprises a core, a first shell grown and formed on the surface of the core, and a second shell grown and formed on the surface of the core or the surface of the first shell. Besides, the core, the first shell, and the second shell are a low energy gap material, a middle energy gap material, and a high energy gap material, respectively. Therefore, the nanocrystal has a great absorption in the ultraviolet range, the visible light range, and the infrared range; and the solar spectrum can be converted effectively to improve the light conversion efficiency thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a to 1c show a schematic diagram of a nanocrystal according to a preferred embodiment of the present invention;

FIGS. 2 a to 2c are transmission electron micrographs (TEM) of the nanocrystal according to a preferred embodiment of the present invention;

FIG. 3 is a schematic diagram of a photovoltaic device according to a preferred embodiment of the present invention;

FIG. 4 is a schematic diagram of a photovoltaic device according to another preferred embodiment of the present invention; and

FIG. 5 is a schematic diagram of a photovoltaic device according to yet another preferred embodiment of the present invention.

Claims

1. A nanocrystal, comprising: a core;a first shell grown from the surface of the core; anda second shell grown from the surface of the core or the surface of the first shell;wherein the core is a low energy gap material having an energy gap that ranges from 1.24 eV to 0.41 eV, the first shell is a middle energy gap material having an energy gap that ranges from 2.48 eV to 1.24 eV, and the second shell is a high energy gap material having an energy gap that ranges from 6.20 eV to 2.48 eV.

2. The nanocrystal as claimed in claim 1, wherein the low energy gap material is a group II-VI semiconductor, the middle energy gap material is a group III-V semiconductor, and the high energy gap material is a group IV semiconductor.

3. The nanocrystal as claimed in claim 1, wherein the high energy gap material is at least one compound selected from a group consisting of MgS, MgSe, MgTe, MnS, MnSe, MnTe, ZnS, ZnSe, GaN, SiC, TiO2, C derivatives, and an alloy thereof.

4. The nanocrystal as claimed in claim 1, wherein the middle energy gap material is at least one compound selected from a group consisting of ZnTe, CdS, CdSe, CdTe, HgS, HgI2, PbI2, InP, GaP, TlBr, C derivatives, and an alloy thereof.

5. The nanocrystal as claimed in claim 1, wherein the low energy gap material is at least one compound selected from a group consisting of PbS, PbSe, PbTe, HgSe, HgTe, InAs, InSb, GaSb, Si, Ge, and an alloy thereof.

6. The nanocrystal as claimed in claim 1, wherein the low energy gap material, the middle energy gap material, or the high energy gap material is an inorganic light absorption material.

7. The nanocrystal as claimed in claim 3, wherein the inorganic light absorption material is at least one compound selected from a group consisting of PbS, PbSe, and TiO2.

8. The nanocrystal as claimed in claim 1, wherein the shape of the nanocrystal is a rod, a tetrapod, a radial form, an arrow, a teardrop, an irregular form, or a combination thereof.

9. The nanocrystal as claimed in claim 8, wherein the shape of the nanocrystal is a rod, a tetrapod, a radial form, or a combination thereof.

10. The nanocrystal as claimed in claim 1, wherein the core is a quantum dot.

11. The nanocrystal as claimed in claim 10, wherein the core comprises ZnSe, ZnSe/ZnS, ZnSe/ZnSeS, ZnS, or ZnTe.

12. The nanocrystal as claimed in claim 1, wherein the core comprises ZnSe, ZnS, or ZnTe.

13. The nanocrystal as claimed in claim 1, wherein the first shell comprises CdSe.

14. The nanocrystal as claimed in claim 1, wherein the second shell comprises PbSe.

15. The nanocrystal as claimed in claim 1, wherein the core comprises ZnSe, or ZnTe, the first cell comprises CdSe, and the second shell comprises PbSe.

16. A photovoltaic device, comprising: a top substrate having a first electrode thereon;a bottom substrate having a second electrode thereon; anda photoactive layer disposed between the first electrode and the second electrode, and the photoactive layer comprises plural nanocrystals, and a conductive material;wherein the nanocrystal comprises a core, a first shell grown from the surface of the core, and a second shell grown from the surface of the core or the surface of the first shell; and wherein the core is a low energy gap material having an energy gap that ranges from 1.24 eV to 0.41 eV, the first shell is a middle energy gap material having an energy gap that ranges from 2.48 eV to 1.24 eV, and the second shell is a high energy gap material having an energy gap that ranges from 6.20 eV to 2.48 eV.

17. The photovoltaic device as claimed in claim 16, wherein the conductive material comprises an organic conductive material, an inorganic conductive material, or a combination thereof.

18. The photovoltaic device as claimed in claim 16 wherein the conductive material is at least one compound selected from a group consisting of N,N′-di(naphthalen)-N,N′-diphenyl-benzidine(NPB), N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine(α-NPB), N,N′-di(naphthalene-1-yl)N,N′-diphenyl-9,9,-dimethyl-fluorene(DMFL-NPB), N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-spiro(Spiro-NPB), N,N′-Bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine (TPD), N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-spiro (Spiro-TPD), N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-9,9-diphenyl-fluorene(DMFL-TPD), 1,3-bis(carbazol-9-yl)-benzene(MCP), 1,3,5-tris(carbazol-9-yl)-benzene(TCP), N,N,N′,N′-tetrakis(naphth-1-yl)-benzidine(TNB), poly(N-vinyl carbazole) (PVK), poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene)(MEH-PPV), poly[2-Methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene-co-4,4′-bisphenylenevinylene](MEH-BP-PPV), poly[(9,9-dioctylfluoren-2,7-diyl)-co-(1,4-diphenylene-vinylene-2-methoxy-5-{2-ethylhexyloxy}benzene)](PF-BV-ME), poly[(9,9-dioctylfluoren-2,7-diyl)-co-(2,5-dimethoxy benzen-1,4-diyl)](PF-DMOP), poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)](PFH), poly[(9,9-dihexylfluoren-2,7-diyl)-co-(9-ethylcarbazol-2,7-diyl)](PFH-EC), poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy}phenylen-1,4-diyl)](PFH-MEH), poly[(9,9-dioctylfluoren-2,7-diyl)(PFO), poly[(9,9-di-n-octylfluoren-2,7-diyl)-co-(1,4-vinylenephenylene)](PF-PPV), poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)](PF-PH), poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(9,9′-spirobifluoren-2,7-diyl)](PF-SP), poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine(poly-TPD) poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl) benzidine(poly-TPD-POSS), poly[(9,9-dihexylfluoren-2,7-diyl)-co-(N,N′-di(4-butylphenyl)-N,N′-diphenyl-4,4′-diyl-1,4-diamino benzene)](TAB-PFH), N,N′-pis(phenanthren-9-yl)-N,N′-diphenylbenzidine(PPB), tris-(8-hydroxy quinoline)-aluminum(Alq3), bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)-aluminium(BAlq3), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline(BCP), 4,4′-bis(carbazol-9-yl) biphenyl(CBP), 3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole(TAZ), MEH-PPV, MEH-BP-PPV, PF, PF-BV-MEH, PF-DMOP, PFH, PFH-EC, PFH-MEH, PFO, PFOB, PF-PPV, PF-PH, PF-SP, poly-TPD, poly-TPD-POSS, TAB-PFH, and PPB.

19. The photovoltaic device as claimed in claim 16, wherein the photoactive layer is electrically connected to the first electrode and the second electrode.

20. The photovoltaic device as claimed in claim 16, wherein the top substrate or the bottom substrate further comprises a carrier transfer layer.

21. The photovoltaic device as claimed in claim 16, wherein the nanocrystals are randomly dispersed in the conductive material.

22. The photovoltaic device as claimed in claim 16, wherein the nanocrystals are uniformly dispersed in the conductive material.

23. The photovoltaic device as claimed in claim 16, wherein the nanocrystals are dispersed in the conductive material in the manner of concentration gradient.

24. The photovoltaic device as claimed in claim 16, wherein the photoactive layer comprises the nanocrystals in an amount of 70% to 90% by weight, and the conductive material in an amount of 10% to 30% by weight.

25. The photovoltaic device as claimed in claim 16, wherein the core, the first shell, or the second shell is an inorganic light-absorption material composed of PbS, PbSe, TiO2, or a combination thereof.

26. The photovoltaic device as claimed in claim 16, wherein the low energy gap material is a group II-VI semiconductor, the middle energy gap material is a group III-V semiconductor, and the high energy gap material is a group IV semiconductor.

27. The photovoltaic device as claimed in claim 16, wherein the shape of nanocrystal is a tetrapod.

28. The photovoltaic device as claimed in claim 16, wherein the core is a quantum dot.

29. The photovoltaic device as claimed in claim 16, wherein the core comprises ZnSe, or ZnTe, the first cell comprises CdSe, and the second shell comprises PbSe.

30. The photovoltaic device as claimed in claim 16, wherein at least one of the top substrate and the bottom substrate is a flexible substrate.