Light detecting element
This light detecting element has a simple configuration, and is highly sensitive to a prescribed wavelength region. The light detecting element comprises a positive electrode, a negative electrode, and an active layer that is provided between the positive electrode and the negative electrode, and that includes a p-type semiconductor material and n-type semiconductor material. The thickness of the active layer is at least 800 nm. The weight ratio between the p-type semiconductor material and the n-type semiconductor material included in the active layer (p/n ratio) is at most 99/1. The work function of the negative electrode side surface in contact with the active layer is lower than the absolute value of the LUMO energy level of the n-type semiconductor material.
1. A light detecting element comprising:
a positive electrode;
a negative electrode; and
an active layer provided between the positive electrode and the negative electrode and containing a p-type semiconductor material and an n-type semiconductor material,
wherein a thickness of the active layer is at least 800 nm,
a weight ratio (p/n ratio) of the p-type semiconductor material to the n-type semiconductor material contained in the active layer is at most 99/1, and
a work function of a surface in contact with the active layer on the negative electrode side is lower than an absolute value of a LUMO energy level of the n-type semiconductor material.
2. The light detecting element according to claim 1 , wherein external quantum efficiency has a narrow peak in a near infrared wavelength region.
3. The light detecting element according to claim 2 , wherein a full width at half maximum of the narrow peak is at most less than 300 nm.
4. The light detecting element according to claim 1 , wherein the surface is a surface of an electron transport layer provided between the negative electrode and the active layer.
5. The light detecting element according to claim 1 , wherein the n-type semiconductor material is a fullerene derivative.
6. The light detecting element according to claim 5 , wherein the fullerene derivative is C70PCBM.
7. The light detecting element according to claim 2 , wherein in a visible light wavelength region, the external quantum efficiency at the maximum absorption wavelength of the active layer is at most 20% of the maximum value of the external quantum efficiency of the narrow peak.
8. An image sensor including the light detecting element according to claim 1 .
9. The light detecting element according to claim 2 , wherein the surface is a surface of an electron transport layer provided between the negative electrode and the active layer.
10. The light detecting element according to claim 3 , wherein the surface is a surface of an electron transport layer provided between the negative electrode and the active layer.
11. The light detecting element according to claim 2 , wherein the n-type semiconductor material is a fullerene derivative.
12. The light detecting element according to claim 3 , wherein the n-type semiconductor material is a fullerene derivative.
13. The light detecting element according to claim 4 , wherein the n-type semiconductor material is a fullerene derivative.
14. The light detecting element according to claim 3 , wherein in a visible light wavelength region, the external quantum efficiency at the maximum absorption wavelength of the active layer is at most 20% of the maximum value of the external quantum efficiency of the narrow peak.
15. The light detecting element according to claim 4 , wherein in a visible light wavelength region, the external quantum efficiency at the maximum absorption wavelength of the active layer is at most 20% of the maximum value of the external quantum efficiency of the narrow peak.
16. The light detecting element according to claim 5 , wherein in a visible light wavelength region, the external quantum efficiency at the maximum absorption wavelength of the active layer is at most 20% of the maximum value of the external quantum efficiency of the narrow peak.
17. The light detecting element according to claim 6 , wherein in a visible light wavelength region, the external quantum efficiency at the maximum absorption wavelength of the active layer is at most 20% of the maximum value of the external quantum efficiency of the narrow peak.
18. An image sensor including the light detecting element according to claim 2 .
19. An image sensor including the light detecting element according to claim 3 .
20. An image sensor including the light detecting element according to claim 4 .