Pyridinium compounds and their use in a photoelectrochemical cell

An electrolyte containing a 6-membered nitrogen-containing aromatic ring compound having a specific structure represented by formula (I') and a photo-electrochemical cell having the electrolyte. The electrolyte hardly volatilizes and performs an excellent charge transport function to provide a photo-electro-chemical cell having excellent photoelectric characteristics and durability. wherein Z' represents an atomic group necessary to form a 6-membered aromatic ring cation together with the nitrogen atom; R1' represents an alkyl group or an alkenyl group; and a' represents 1 or 3.