Organic light receiving element and light receiving device
An organic light-receiving element includes an organic light-receiving layer containing a plurality of organic semiconductor molecules. Each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from a lowest excited triplet state to a lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules due to irradiation with light.
1 . A light-receiving device, comprising:
an organic light-receiving element; and
a controller electrically connected to the organic light-receiving element,
wherein the organic light-receiving element including:
a first electrode;
a second electrode; and
an organic light-receiving layer disposed between the first electrode and the second electrode and containing a plurality of organic semiconductor molecules,
wherein each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from a lowest excited triplet state to a lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules due to irradiation with light, and
the controller is configured to adjust a potential difference between the first electrode and the second electrode in a light-receiving period so that an electric field in a direction of causing charge separation occurs in the organic light-receiving layer, and detect a current generated by the charge separation.
2 . The light-receiving device according to claim 1 ,
wherein in each of the plurality of organic semiconductor molecules, a difference between energy of the lowest excited singlet state and energy of the lowest excited triplet state at an absolute temperature of 77 K is less than 0.3 eV.
3 . The light-receiving device according to claim 1 ,
wherein in each of the plurality of organic semiconductor molecules, an intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is greater than a radiative decay rate constant from the lowest excited singlet state to the ground state.
4 . The light-receiving device according to claim 1 ,
wherein in each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is greater than a reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state.
5 . The light-receiving device according to claim 4 ,
wherein in each of the plurality of organic semiconductor molecules, the intersystem crossing rate constant from the lowest excited singlet state to the lowest excited triplet state is two or more times the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state.
6 . The light-receiving device according to claim 4 ,
wherein in each of the plurality of organic semiconductor molecules, the reverse intersystem crossing rate constant from the lowest excited triplet state to the lowest excited singlet state is 1×10 7 (sec −1 ) or less.
7 . The light-receiving device according to claim 1 ,
wherein a dipole moment of each of the plurality of organic semiconductor molecules is greater than 0 D.
8 . The light-receiving device according to claim 1 ,
wherein the light-receiving layer further contains a plurality of host molecules, and
energy of the lowest excited triplet state at an absolute temperature of 77 K in each of the plurality of host molecules is higher than energy of the lowest excited triplet state at an absolute temperature of 77 K in each of the plurality of organic semiconductor molecules.
9 . The light-receiving device according to claim 1 ,
wherein at least one of the first electrode and the second electrode has a light-transmitting property with respect to light emitted to the light-receiving layer.
10 . The light-receiving device according to claim 1 , further comprising:
a charge block layer disposed at any one of a first position between the light-receiving layer and the first electrode, and a second position between the light-receiving layer and the second electrode.
11 . The light-receiving device according to claim 10 , further comprising:
a charge transport layer disposed at the other of the first position and the second position.
12 . The light-receiving device according to claim 10 ,
wherein the controller applies a voltage between the first electrode and the second electrode in an application period after passage of a holding period from the light-receiving period so that an electric field in a direction opposite to the direction of causing the charge separation occurs in the organic light-receiving layer.