Photoelectric conversion element and solid-state imaging device
A photoelectric conversion element according to an embodiment of the present disclosure includes: a first electrode and a second electrode facing each other; and a photoelectric conversion layer provided between the first electrode and the second electrode, and including a first organic semiconductor material, a second organic semiconductor material, and a third organic semiconductor material that have mother skeletons different from one another. The first organic semiconductor material is one of fullerenes and fullerene derivatives. The second organic semiconductor material in a form of a single-layer film has a higher linear absorption coefficient of a maximal light absorption wavelength in a visible light region than a single-layer film of the first organic semiconductor material and a single-layer film of the third organic semiconductor material. The third organic semiconductor material has a value equal to or higher than a HOMO level of the second organic semiconductor material.
1. A photoelectric conversion element, comprising:
a first electrode and a second electrode facing each other; and
a photoelectric conversion layer provided between the first electrode and the second electrode, and including a first organic semiconductor material, a second organic semiconductor material, and a third organic semiconductor material that have mother skeletons different from one another,
wherein the first organic semiconductor material is fullerene,
wherein the second organic semiconductor material formed as a single-layer film has a linear absorption coefficient of a maximal light absorption wavelength in a visible light region higher than a linear absorption coefficient of a maximal light absorption wavelength in the visible light region of a single-layer film of the first organic semiconductor material and a linear absorption coefficient of a maximal light absorption wavelength in the visible light region of a single-layer film of the third organic semiconductor material,
wherein the third organic semiconductor material is a hole-transporting material, and
wherein the linear absorption coefficient of the maximal light absorption wavelength in the visible light region of the second organic semiconductor material is more than ten times a linear absorption coefficient of a wavelength with 450 nm of the second organic semiconductor material.
2. The photoelectric conversion element according to claim 1 , wherein the fullerene comprises C60 fullerene.
3. The photoelectric conversion element according to claim 1 , wherein the fullerene comprises C70 fullerene.
4. The photoelectric conversion element according to claim 1 , wherein the fullerene comprises C60 fullerene and C70 fullerene.
5. The photoelectric conversion element according to claim 1 , wherein the third organic semiconductor material when formed as a single-layer film has a higher hole mobility than a hole mobility of the single-layer film of the second organic semiconductor material.
6. The photoelectric conversion element according to claim 1 , wherein the third organic semiconductor material has a value equal to or higher than a highest occupied molecular orbital (HOMO) level of the second organic semiconductor material.
7. The photoelectric conversion element according to claim 1 , wherein in the photoelectric conversion layer, excitons generated through light absorption by the second organic semiconductor material are separated at an interface between two organic semiconductor materials selected from the first organic semiconductor material, the second organic semiconductor material, and the third organic semiconductor material.
8. The photoelectric conversion element according to claim 1 , wherein the photoelectric conversion layer has a maximal absorption wavelength in a range from 450 nm to 650 nm, both inclusive.
9. The photoelectric conversion element according to claim 1 , wherein the third organic semiconductor material includes a hetero element other than carbon (C) and hydrogen (H) in a molecule of the third organic semiconductor material.
10. The photoelectric conversion element according to claim 1 , wherein the photoelectric conversion layer includes the first organic semiconductor material in a range from 10 vol % to 35 vol %, both inclusive.
11. The photoelectric conversion element according to claim 1 , wherein the photoelectric conversion layer includes the second organic semiconductor material in a range from 30 vol % to 80 vol %, both inclusive.
12. The photoelectric conversion element according to claim 1 , wherein the photoelectric conversion layer includes the third organic semiconductor material in a range from 10 vol % to 60 vol %, both inclusive.
13. The photoelectric conversion element according to claim 1 , wherein one of the second organic semiconductor material and the third organic semiconductor material is a quinacridone derivative represented by the following formula (1):
where each of R1 and R2 is independently one of a hydrogen atom, an alkyl group, an aryl group, and a heterocyclic group, each of R3 and R4 is independently one of an alkyl chain, an alkenyl group, an alkynyl group, an aryl group, a cyano group, a nitro group, and a silyl group, and two or more of R3 or two or more of R4 optionally form a ring together, and each of n1 and n2 is independently 0 or an integer of 1 or more.
14. The photoelectric conversion element according to claim 1 , wherein one of the second organic semiconductor material and the third organic semiconductor material is one of a triallylamine derivative represented by the following formula (2) and a benzothienobenzothiophene derivative represented by the following formula (3):
where each of R20 to R23 is independently a substituent represented by a formula (2)′, each of R24 to R28 is independently one of a hydrogen atom, a halogen atom, an aryl group, an aromatic hydrocarbon ring group, an aromatic hydrocarbon ring group having an alkyl chain or a substituent, an aromatic heterocyclic group, and an aromatic heterocyclic group having an alkyl chain or a substituent, adjacent ones of R24 to R28 are optionally saturated or unsaturated divalent groups that are bound to one another to form a ring, and
where each of R5 and R6 is independently one of a hydrogen atom and a substituent represented by a formula (3)′, and R7 is one of an aromatic ring group and an aromatic ring group having a substituent.
15. The photoelectric conversion element according to claim 1 , wherein one of the second organic semiconductor material and the third organic semiconductor material is a subphthalocyanine derivative represented by the following formula (4):
where each of R8 to R19 is independently selected from a group consisting of a hydrogen atom, a halogen atom, a straight-chain, branched, or cyclic alkyl group, a thioalkyl group, a thioaryl group, an arylsulfonyl group, an alkylsulfonyl group, an amino group, an alkylamino group, an arylamino group, a hydroxy group, an alkoxy group, an acylamino group, an acyloxy group, a phenyl group, a carboxy group, a carboxyamide group, a carboalkoxy group, an acyl group, a sulfonyl group, a cyano group, and a nitro group, any adjacent ones of R8 to R19 are optionally part of a condensed aliphatic ring or a condensed aromatic ring, the condensed aliphatic ring or the condensed aromatic ring optionally includes one or more atoms other than carbon, M is one of boron and a divalent or trivalent metal, and X is an anionic group.
16. The photoelectric conversion element according to claim 1 , wherein the second organic semiconductor material is a subphthalocyanine derivative, and the third organic semiconductor material is a quinacridone derivative.
17. The photoelectric conversion element according to claim 1 , wherein the second organic semiconductor material is a subphthalocyanine derivative and the third organic semiconductor material is a triallylamine derivative or a benzothienobenzothiophene derivative.
18. The photoelectric conversion element according to claim 1 , wherein the fullerene is represented by one of the following formulas (5) and (6):
where each R is a hydrogen atom.
19. The photoelectric conversion element according to claim 1 , wherein the photoelectric conversion layer includes a fourth organic semiconductor material having a same mother skeleton as a mother skeleton of one of the first organic semiconductor material, the second organic semiconductor material, and the third organic semiconductor material, and having a different substituent.
20. The photoelectric conversion element according to claim 1 , wherein the visible light region is in a range from 450 nm to 800 nm, both inclusive.
21. A light detecting device provided with pixels, each including one or more organic photoelectric converters, each of the organic photoelectric converters comprising:
a first electrode and a second electrode facing each other; and
a photoelectric conversion layer provided between the first electrode and the second electrode, and including a first organic semiconductor material, a second organic semiconductor material, and a third organic semiconductor material that have mother skeletons different from one another,
wherein the first organic semiconductor material is fullerene,
wherein the second organic semiconductor material in a form of a single-layer film has a linear absorption coefficient of a maximal light absorption wavelength in a visible light region higher than a linear absorption coefficient of a maximal light absorption wavelength in the visible light region of a single-layer film of the first organic semiconductor material and a linear absorption coefficient of a maximal light absorption wavelength in the visible light region of a single-layer film of the third organic semiconductor material,
wherein the third organic semiconductor material is a hole-transporting material; and
wherein the linear absorption coefficient of the maximal light absorption wavelength in the visible light region of the second organic semiconductor material is more than ten times a linear absorption coefficient of a wavelength with 450 nm of the second organic semiconductor material.
22. The light detecting device according to claim 21 , wherein the one or more organic photoelectric converters, and one or more inorganic photoelectric converters that perform photoelectric conversion in a wavelength region different from a wavelength region of the organic photoelectric converters, are stacked in each of the pixels.
23. The light detecting device according to claim 22 , wherein the one or more inorganic photoelectric converters are formed to be embedded in a semiconductor substrate, and wherein the one or more organic photoelectric converters are formed on a first surface side of the semiconductor substrate.
24. The light detecting device according to claim 23 , wherein the one or more organic photoelectric converters perform photoelectric conversion on green light, and wherein an inorganic photoelectric converter that performs photoelectric conversion on blue light and an inorganic photoelectric converter that performs photoelectric conversion on red light are stacked in the semiconductor substrate.