he present invention is directed to capacitive energy storage devices based on polyimide-metal phthalocyanine (PI-MPC) nanocomposites containing both high breakdown strength and high dielectric constant (κ) moieties. The present devices exhibit linear charge displacement-electric field (D-E) characteristics with small remnant polarization and small hysteresis, and can be utilized for high breakdown strength, high energy density and low energy loss energy storage applications. More exactly, the present invention is directed to basic capacitive energy storage elements and high energy density storage capacitor arrays which comprise films of PI-MPC prepared by solution processing techniques. The present invention also relates to using polyimide and metal phthalocyanine as the active dielectric materials, in the form of, but not limited to, physical blends, covalent-bonded molecular composites and nanocomposites for energy storage applications. The present invention also relates to utilizing polyimides including, but not limited to, aromatic polyimide derivatives, as the high breakdown strength component in the active dielectric materials. The present invention also relates to utilizing metal phthalocyanine including, but not limited to, copper phthalocyanine (CuPC), zinc phthalocyanine (ZnPC), aluminum phthalocyanine (AlPC), cobalt phthalocyanine (CoPC), nickel phthalocyanine (NiPC), tin phthalocyanine (SnPC), iron phthalocyanine (FePC), palladium phthalocyanine (PdPC) and platinum phthalocyanine (PtPC) as the high dielectric constant (κ) component in the active dielectric materials.