TECHNOLOGY FOCUS - POLYMERS - Preferred compound: The random copolymer is represented with a formula (1).m+l+k=1;l+k= 0.53-0.63;andn=80-1000.Preferred Process: The neutral matrix is formed by coating the photo-curable random copolymer and irradiating the ultraviolet ray in the vacuum condition. The polymethyl methacrylate domain is removed from the block copolymer film by annealing at the temperature of 150-190 degrees C under vacuum. The polymethyl methacrylate domain included in the block copolymer film is removed by irradiating ultraviolet having wavelength of 200-400 nm on the top of the block copolymer film. The etching process is done using fluorine group or chlorine-based gas. Preferred Properties: The molar fraction of the monomer is 0.02-0.04. The average molecular weight of the random copolymer is 8000-100000. The intensity of the ultraviolet ray is 1.4-5.3mW / cm2 and the scanning time of the ultraviolet ray is 2~20 minutes. The thickness of the neutral matrix is 5-10nm. The thickness of the block copolymer film is 25-40nm. The molar ratio of the polymethyl metacrylate and the polystyrene comprised in the block copolymer film is 7:3. The average molecular weight of the block copolymer in the block copolymer film is 50000-90000. The nano pattern is cylindrical or lamellar in shape of the vertical direction in the solar cell light emitting surface. EXAMPLE - Methyl 2-(benzodithiol)-2-phenyl acetate (35.3 mg), methylmethacrylate (2.4 g), styrene (3.6 g), 4- vinylbenzene chloride (0.27 g) and reversible addition fragmentation chain transfer initiator are mixed to form a mixture. The gas was removed from the mixture and heated at a temperature of 70 degrees C in a vacuum condition. The obtained product was dissolved in dichloromethane and precipitated by adding methanol. A random copolymer was obtained. The obtained copolymer was mixed with toluene and reacted at 80 degrees C for 4 hours using methanol. The obtained white powder was dissolved in dimethylformamide with the sodium azide of 3 equivalents and agitated at room temperature. The resulting solution was filtered and thermal cross-linkable random copolymer with the molecular weight of 35000 was obtained at yield of 37%. The obtained copolymer of 0.4 weight% was melted in toluene and was coated on a substrate to obtain a random copolymer film of 12 nm thickness. The film was laminated on upper side of neutral matrix and was cross-linked. The surface of substrate was etched and a solar cell of 50 nm was manufactured with excellent quantum efficiency.