Patent ID: 8778233

Claim:
A positive hole injection transport layer-forming ink for producing a transition metal-containing nanoparticle containing at least a protecting agent, a transition metal and a transition metal compound including a transition metal oxide, or at least a protecting agent and a transition metal compound including a transition metal oxide, the ink comprising an organic solvent and a transition metal-containing nanoparticle containing a protecting agent and a transition metal and/or transition metal compound, wherein a surface of the nanoparticles is attached to the protecting agent which protects the surface of the nanoparticles; the protecting agent contains an organic group and one linking group at the end of the organic group in one molecule; the linking group functions to connect to the transition metal and/or the transition metal compound; the organic group is one or more selected from the group consisting of a linear or branched saturated or unsaturated alkyl group having 4 to 30 carbon atoms, and benzene, triphenylamine, fluorene, biphenyl, pyrene, anthracene, carbazole, phenylpyridine, trithiophene, phenyloxadiazole, phenyltrizaole, benzimidazole, phenyltriazine, benzodiathiazine, phenylquinoxaline, phenylenevinylene, phenylsilole and combinations thereof, each of which may have a substituent selected from the group consisting of a linear or branched alkyl group having 1 to 20 carbon atoms, a halogen atom, an alkoxy group having 1 to 20 carbon atoms, a cyano group and a nitro group; and the linking group is one or more kinds selected from the group consisting of a hydroxyl group, a sulfonic acid group, a sulfonamide group and functional groups represented by the following general formulae (1-a) to (1-l): wherein each of Z 1 , Z 2 and Z 3 independently represents a halogen atom or an alkoxy group.