NOVELTY - Electrical device comprises a first electrode comprising least one dendritic metal structure; a second electrode; and an electrically active structure disposed between the dendritic metal structure and the second electrode; or electrical device comprises an insulator; and an electrode comprising least one dendritic metal structure disposed on the insulator.    USE - The electrical device is useful for producing solar cell, photodetector, and touch screen (all claimed).    ADVANTAGE - The invention provides electrode designs that can provide efficient electrical properties (e.g. current collection and field maintenance) while not blocking too much of the electrically active structure from light.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a method for making electrical structure comprising: disposing the electrically active structure on the second electrode; disposing a solid electrolyte on the electrically active structure; disposing an anode comprising a metal, and a cathode in electrical contact with the solid electrolyte; and applying a bias voltage across the cathode and the anode sufficient to grow the dendritic metal structure extending from the cathode, the dendritic metal structure being formed from the metal of the anode; or a method for making an electrical structure comprising an electrode, comprising a dendritic metal structure, comprising applying a bias voltage across an anode and a cathode in electrical contact with a solid electrolyte, the solid electrolyte having metal dissolved to it, the bias voltage being sufficient to grow the dendritic metal structure extending from the cathode, the dendritic metal structure being formed from the metal; or a method for making an electrical device comprising disposing a solid electrolyte on the insulator; disposing an anode comprising a metal, and a cathode in electrical contact with the solid electrolyte; and applying a bias voltage across the cathode and the anode sufficient to grow the dendritic metal structure extending from the cathode, the dendritic metal structure being formed from the metal of the anode;    (2) a solar cell comprising the electrical device or electrical device made by the method above;    (3) a photodetector comprising the electrical device or electrical device made by the method above; and    (4) a touch screen comprising the electrical device or electrical device made by the method above.