NOVELTY - The method involves forming a metal droplet on a substrate by droplet epitaxy by controlling height or aspect ratio of the formed metal droplet by adjusting growth temperature of the metal droplet. A non-metal is deposited on the formed metal droplet. A nano-compound crystal (40) is formed by a self-assembly of the deposited non-metal and the metal droplet, where the metal droplet is provided in a liquid state, and temperature of the substrate, injection time and injection amount of the non-metal are adjusted to control shape of the nano compound crystal.    USE - Method for manufacturing a film-shaped anti-reflection coating using a self-assembly nano- structure for a photoelectric device e.g. solar cell or LED.    ADVANTAGE - The method enables forming the nano compound crystal by self- assembly of the deposited non-metal and the metal droplet and manufacturing or foaming an anti-reflection coating using a self-assembly nano structure at an upper portion of a photoelectric device by droplet epitaxy regardless of substrate materials such that an optical absorption factor or an optical emission factor can be maximized by reducing optical absorption of the anti-reflection coating and transferring greater amount of light to an active layer or to outside when etching process eliminates defect caused by etching, thus improving efficiency and quality of the photoelectric device.    DETAILED DESCRIPTION - The shape of the nano compound crystal is selected from a group consisting of a large nano dome, a nano tip, a nano rod or a nano cone. The metal droplet is selected from a group consisting of gallium, phosphorus and aluminum. The non-metal is selected from a group consisting of arsenic, antimony, phosphorus and nitrogen. An INDEPENDENT CLAIM is also included for an anti-reflection coating using a self-assembly nano structure.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a substrate.    N-type gallium arsenic layer (1)    Gallium arsenic buffer layer (2)    Aluminum gallium arsenic layer (3)    Nano-compound crystal (40)