The present disclosure discloses metal oxide nanoparticle ink, a method of preparing the same, a metal oxide nanoparticle thin film manufactured using the same, and a photoelectric device using the same. The method of preparing metal oxide nanoparticle ink according to an embodiment of the present disclosure includes a step of, using a ligand solution including a metal oxide and an organic ligand, synthesizing a first nanoparticle that is a metal oxide nanoparticle surrounded with the organic ligand; a step of preparing a dispersion solution by dispersing the first nanoparticle in a solvent; a step of preparing a second nanoparticle by mixing the dispersion solution and a pH-adjusted alcohol solvent and then performing ultrasonication treatment to remove the organic ligand surrounding the first nanoparticle; and a step of preparing metal oxide nanoparticle ink by dispersing the second nanoparticle in a dispersion solvent.

A solid-state imaging element including: a photoelectric conversion layer, a first electrode and a second electrode opposed to each other with the photoelectric conversion layer interposed therebetween, a semiconductor layer provided between the first electrode and the photoelectric conversion layer, an accumulation electrode opposed to the photoelectric conversion layer with the semiconductor layer interposed therebetween, an insulating film provided between the accumulation electrode and the semiconductor layer, and a barrier layer provided between the semiconductor layer and the photoelectric conversion layer.

A polymer comprising an electron-donating repeat unit of formula (I) and an electron-accepting repeat unit: -(A).sub.n- (I) wherein A in each occurrence is independently a group of formula (II): Y in each occurrence is independently O or S. Z is O, S or NR.sup.3 wherein R.sup.3 is H or a substituent. R.sup.1 in each occurrence is independently H or a substituent. R.sup.2 in each occurrence is independently a substituent, n is at least 2. The polymer may be used as an electron-donating polymer in combination with an electron-accepting material in a bulk heterojunction layer of an organic photodetector.

##STR00001##

A polymer comprising an electron-donating repeat unit of formula (I) and an electron-accepting repeat unit: -(A).sub.n- (I) wherein A in each occurrence is independently a group of formula (II): Y in each occurrence is independently O or S. Z is O, S or NR.sup.3 wherein R.sup.3 is H or a substituent. R.sup.1 in each occurrence is independently H or a substituent. R.sup.2 in each occurrence is independently a substituent, n is at least 2. The polymer may be used as an electron-donating polymer in combination with an electron-accepting material in a bulk heterojunction layer of an organic photodetector.

##STR00001##

An imaging device includes: a first electrode; a charge storage electrode disposed at a distance from the first electrode; a photoelectric conversion layer in contact with the first electrode and above the charge storage electrode, with an insulating layer between the charge storage electrode and the photoelectric conversion layer; and a second electrode on the photoelectric conversion layer. The portion of the insulating layer between the charge storage electrode and the photoelectric conversion layer includes a first region and a second region, the first region is formed with a first insulating layer, the second region is formed with a second insulating layer, and the absolute value of the fixed charge of the material forming the second insulating layer is smaller than the absolute value of the fixed charge of the material forming the first insulating layer.

The present invention is to provide a photoelectric conversion element with an excellent sensitivity, an imaging element, an optical sensor, and a compound. The photoelectric conversion element according to the embodiment of the present invention includes, in the following order, a conductive film, a photoelectric conversion film, and a transparent conductive film, in which the photoelectric conversion film contains a compound represented by Formula (1) and a coloring agent.

A-D-A  (1)

An infrared absorption composition includes a p-type semiconductor compound including a first structural unit represented by Chemical Formula 1 and a second structural unit including an electron donating moiety; and an n-type semiconductor compound represented by Chemical Formula 2:

##STR00001## wherein, in Chemical Formula 1, Ar.sup.1, X, R.sup.1a, and R.sup.2a are the same as defined in the detailed description. In Chemical Formula 2, A.sup.1, A.sup.2, D.sup.1, D.sup.2, and D.sup.3 are the same as defined in the detailed description.

An infrared absorption composition includes a p-type semiconductor compound including a first structural unit represented by Chemical Formula 1 and a second structural unit including an electron donating moiety; and an n-type semiconductor compound represented by Chemical Formula 2:

##STR00001## wherein, in Chemical Formula 1, Ar.sup.1, X, R.sup.1a, and R.sup.2a are the same as defined in the detailed description. In Chemical Formula 2, A.sup.1, A.sup.2, D.sup.1, D.sup.2, and D.sup.3 are the same as defined in the detailed description.

An photoelectric conversion element in the disclosure is characterized by including: a first conductive layer; a porous hole-blocking layer disposed on the first conductive layer; a porous insulator layer disposed on the porous hole-blocking layer; photoabsorption layers disposed in a pore of the porous hole-blocking layer and in a pore of the porous insulator layer and containing an organic-based photoelectric conversion material; an electron-blocking layer disposed on the porous insulator layer; and a second conductive layer disposed on the electron-blocking layer.

The present disclosure provides a photoelectric conversion element including a first electrode 3, a second electrode 7, a photoelectric conversion layer 5 between the first electrode 3 and the second electrode 7, and a reflection layer 6 between one of the first electrode 3 and the second electrode 7 and the photoelectric conversion layer 5. The wavelength at which the reflectance of the reflection layer 6 is maximum in the visible region is within the range of wavelengths in which the optical absorption coefficient of the photoelectric conversion layer 5 is ⅕ or more of the maximum optical absorption coefficient in the visible region.