NOVELTY - Modifying counter electrode (300) surface involves disposing an electrically conductive material on a substrate (310); and modifying the surface of the conductive layer (320) with a polyethylene glycol derivative having a pendant group at one end.    USE - For modifying surface of counter electrode for photovoltaic device, e.g. solid dye-sensitized photovoltaic device.    ADVANTAGE - The method promotes the transfer of electrons at the interface between the counter electrode and a polymer electrolyte of photovoltaic device, leading to a reduction in the interface resistance of the photovoltaic device. The reduced interface resistance increases the current density of the photovoltaic device and, as a result, the redox reaction rate of the photovoltaic device is increased, thus achieving an improved energy conversion efficiency of the photovoltaic device. The surface-modified counter electrode has a high value as an electrode for photovoltaic devices.    DETAILED DESCRIPTION - Modifying counter electrode surface involves disposing an electrically conductive material on a substrate to form a conductive layer; and modifying the surface of the conductive layer with a compound of formula H-X1-((CH2)2-X2)n-R (1).    R = H or OH;    X1 = S (preferred), Se or Te;    X2 = O (preferred), S, Se or Te;    n = 1-40.    INDEPENDENT CLAIMS are included for:    (1) surface-modified counter electrode comprising a substrate; a conductive layer; and a surface-modification coating layer (330); and    (2) photovoltaic device comprising a transparent semiconductor electrode (100) comprising a substrate and a conductive material coated on the substrate; a light-absorbing layer formed on the transparent electrode having a dye (150) adsorbed on it; a counter electrode disposed opposite to the semiconductor electrode; and a redox electrolyte layer (200) formed between the transparent semiconductor electrode and the counter electrode, where the counter electrode comprises a surface-modification coating layer formed from compound (1).    DESCRIPTION OF DRAWING(S) - The figure is a schematic view of a state in which the surface of a counter electrode is modified.    Semiconductor electrode (100)    Dye (150)    Electrolyte layer (200)    Counter electrode (300)    Substrate (310)    Conductive layer (320)    Surface-modification coating layer (330)