To provide a solar cell which has a triplet-triplet annihilation (TTA) based up-conversion mechanism adopted in it.

A solar cell 10 holds an electrolyte 40, which contains a chemical species constituting a redox couple, between a light permeable photoelectrode 20 having an n-type semiconductor and a counter electrode 30 disposed so as to oppose the n-type semiconductor, with emitters and sensitizers coexisting between the photoelectrode 20 and the counter electrode 30. The sensitizers are made to transition to an excited singlet state by light in longer wavelength than the wavelength of the excited light of the emitters, and are thereafter placed into an excited triplet state by intersystem crossing. Next, as the sensitizers in the excited triplet state deliver their energy to the emitters by energy transfer, so the emitters transition to the excited triplet state. Thereafter, triplet-triplet annihilation between the emitters generates emitters in an excited singlet state, and electrons move to the n-type semiconductor via the emitters in the excited singlet state.