Photoelectric conversion device, organic sensor and electronic device

1. A photoelectric conversion device, comprising

a first electrode;

a second electrode on the first electrode;

a photoelectric conversion layer between the first electrode and the second electrode, the photoelectric conversion layer being configured to absorb light in at least one portion of a wavelength spectrum and to convert the absorbed light into an electric signal; and

a buffer layer between the second electrode and the photoelectric conversion layer, the buffer layer including a mixture of at least two materials,

the mixture including a first material and a second material,

the first material having an energy bandgap of greater than or equal to about 3.2 eV and a HOMO energy level of greater than or equal to about 6.0 eV, and

the second material having an energy bandgap of less than or equal to about 2.8 eV and a HOMO energy level of greater than or equal to about 6.0 eV.

2. The photoelectric conversion device of claim 1 , wherein a LUMO energy level of the buffer layer is deeper or shallower within about 30% of a LUMO energy level of the photoelectric conversion layer.

3. The photoelectric conversion device of claim 2 , wherein the LUMO energy level of the buffer layer is about 3.0 eV to about 4.5 eV.

4. The photoelectric conversion device of claim 1 , wherein a HOMO energy level of the buffer layer is deeper than a HOMO energy level of the photoelectric conversion layer by greater than or equal to about 0.5 eV.

5. The photoelectric conversion device of claim 4 , wherein the HOMO energy level of the buffer layer is about 6.0 eV to about 7.0 eV.

6. The photoelectric conversion device of claim 1 , wherein an energy bandgap of the buffer layer is between the energy bandgap of the first material and the energy bandgap of the second material.

7. The photoelectric conversion device of claim 1 , wherein a surface roughness of the buffer layer measured by an atomic force microscope is smaller than a surface roughness of a thin film consisting of the first material and a surface roughness of a thin film consisting of the second material, respectively.

8. The photoelectric conversion device of claim 7 , wherein the surface roughness of the buffer layer is less than or equal to about 1.2 nm.

9. The photoelectric conversion device of claim 1 , wherein the buffer layer has an amorphous structure.

10. The photoelectric conversion device of claim 1 , wherein the first material is an organic material comprising an aromatic ring, a heteroaromatic ring, or a combination thereof, and

the second material is a fullerene or a fullerene derivative.

11. The photoelectric conversion device of claim 10 , wherein the first material is represented by Chemical Formula 1:

wherein, in Chemical Formula 1,

R I to R VIII are independently hydrogen, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C3 to C30 heterocyclic group, a substituted or unsubstituted C1 to C6 alkoxy group, a halogen, or a cyano group, and

R I to R VIII are independently present or an adjacent two thereof are combined to form a ring.

12. The photoelectric conversion device of claim 1 , wherein a mixing volume ratio of the first material and the second material is about 5:5 to about 9:1.

13. The photoelectric conversion device of claim 1 , wherein the photoelectric conversion layer comprises an organic absorbing material configured to selectively absorb one of a blue wavelength spectrum, a green wavelength spectrum, a red wavelength spectrum, and a near infrared wavelength spectrum.

14. The photoelectric conversion device of claim 1 , wherein the first electrode is an anode and the second electrode is a cathode.

15. The photoelectric conversion device of claim 1 , wherein the second electrode is a light-receiving electrode.

16. The photoelectric conversion device of claim 1 , wherein the first material is represented by Chemical Formula 1:

wherein, in Chemical Formula 1,

R I to R VIII are independently hydrogen, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C3 to C30 heterocyclic group, a substituted or unsubstituted C1 to C6 alkoxy group, a halogen, or a cyano group, and

R I to R VIII are independently present or an adjacent two thereof are combined to form a ring.

17. The photoelectric conversion device of claim 1 , wherein the second material is a fullerene or a fullerene derivative.

18. The photoelectric conversion device of claim 1 , wherein

the photoelectric conversion layer includes a p-type semiconductor and an n-type semiconductor,

the energy band gap of the first material is about 3.2 eV to about 4.0 eV,

the HOMO energy level of the first material is about 6.0 eV to about 7.0 eV,

the energy band gap of the second material is about 1.8 eV to about 2.8 eV, and

the HOMO energy level of the second material is about 6.0 eV to about 7.0 eV.

19. The photoelectric conversion device of claim 18 , wherein the p-type semiconductor is represented by Chemical Formula A:

EDM1-LM1-EAM1  [Chemical Formula A]

wherein, in Chemical Formula A,

EDM1 is an electron donating moiety,

EAM1 is an electron accepting moiety, and

LM1 is a π-conjugated linking moiety that links the electron donating moiety and the electron accepting moiety.

20. The photoelectric conversion device of claim 18 , wherein

the n-type semiconductor includes thiophene, a thiophene derivative, fullerene, or a fullerene derivative.

21. An organic sensor comprising:

the photoelectric conversion device of claim 1 .

22. The organic sensor of claim 21 , further comprising:

a semiconductor substrate stacked with the photoelectric conversion device.

23. The organic sensor of claim 22 , further comprising:

a photodiode integrated in the semiconductor substrate.

24. An electronic device comprising:

the organic sensor of claim 21 .

25. An electronic device comprising:

the organic sensor of claim 1 .