the photovoltaic cells 13 are integrated with the secondary battery as shown in the lower figure of fig1 2 the operational voltage of the secondary battery layer is controlled to enable the charging operation in the range of 0 4 to 1 3 v and 3 the secondary battery layer can be implemented on a flexible substrate as well as a rigid substrate to expand the application and improve the durability while showing about the same cycle characteristics as the existing secondary batteries moreover in order to store the output voltage generated from the photovoltaic cells in the secondary battery layer without loss the present invention provides a secondary battery which employs a metal oxide or a metal phosphate as cathode and anode materials of the second battery layer the metal oxide and the metal phosphate which can be used in the is present invention may include a x m y o 2 a li na or k m metal cation 0 lt x lt 1 0 5 lt y lt 2 a x m 2 o 4 a li na or k m metal cation 0 lt x lt 2 limpo 4 m metal cation as the anode material any one selected from the group consisting of lim y fe 1 y po.