Transparent substrate comprising an antireflection coating

Abstract

The subject of the invention is a transparent substrate ( 6 ) having at least one antireflection coating, made from a film (A) comprising multiple thin layers of alternately high and low refractive indexes. The multilayer film comprises, in succession: a high-index first layer ( 1 ), having a refractive index n 1 , of between 1.8 and 2.3 and a geometrical thickness e 1 of between 5 and 50 nm; a low-index second layer ( 2 ), having a refractive index n 2 of between 1.30 and 1.70 and a geometrical thickness e 2 of between 5 and 50 nm; a high-index third layer ( 3 ), having a refractive index n 3 of between 1.8 and 2.3 and a geometrical thickness e 3 of at least 100 nm; a low-index fourth layer ( 4 ), having a refractive index n 4 of between 1.30 and 1.70 and a geometrical thickness e 4 of at least 80 nm. This antireflection coating can be used in solar modules.

1 . Transparent substrate ( 6 ), especially made of glass, having on at least one of its faces an antireflection coating, in particular at least in the visible and in the near infrared, made from a film (A) comprising multiple thin layers of a dielectric having alternately high and low refractive indexes, characterized in that the multilayer film comprises, in succession: 
 a high-index first layer ( 1 ), having a refractive index n 1  of between 1.8 and 2.3 and a geometrical thickness e 1  of between 5 and 50 nm;    a low-index second layer ( 2 ), having a refractive index n 2  of between 1.30 and 1.70 and a geometrical thickness e 2  of between 5 and 50 nm;    a high-index third layer ( 3 ), having a refractive index n 3  of between 1.8 and 2.3 and a geometrical thickness e 3  of at least 100 nm or at least 120 nm;    a low-index fourth layer ( 4 ), having a refractive index n 4  of between 1.30 and 1.70 and a geometrical thickness e 4  of at least 80 nm or at least 90 nm.    
     
     
         2 . Substrate ( 6 ) according to  claim 1 , characterized in that the high-index first layer ( 1 ) and the low-index second layer ( 2 ) are replaced with a single layer ( 5 ) of intermediate index e 5  of between 1.60 and 1.90, especially between 1.70 and 1.80.  
     
     
         3 . Substrate ( 6 ) according to  claim 2 , characterized in that the single layer ( 5 ) of intermediate index has a geometrical thickness e 5  of between 40 and 120 nm, especially between 60 and 100 nm or between 65 and 85 nm.  
     
     
         4 . Substrate ( 6 ) according to one of the preceding claims, characterized in that n 1 , and/or n 3  are between 1.85 and 1.15, especially between 1.90 and 2.10 or between 2.0 and 2.1.  
     
     
         5 . Substrate ( 6 ) according to one of the preceding claims, characterized in that n 2  and/or n 4  are between 1.35 and 1.55 or between 1.40 and 1.50.  
     
     
         6 . Substrate ( 6 ) according to one of the preceding claims, characterized in that e 1  is between 10 and 30 nm, especially between 15 and 25 nm.  
     
     
         7 . Substrate ( 6 ) according to one of the preceding claims, characterized in that e 2  is between 15 and 45 nm, especially between 20 and 40 nm, preferably less than or equal to 35 nm.  
     
     
         8 . Substrate ( 6 ) according to one of the preceding claims, characterized in that e 3  is between 100 and 180 nm and is especially between 140 and 160 nm.  
     
     
         9 . Substrate ( 6 ) according to one of the preceding claims, characterized in that e 4  is greater than or equal to 90 nm and is especially between 95 and 120 nm.  
     
     
         10 . Substrate ( 6 ) according to  claim 2  or  claim 3 , characterized in that the layer ( 5 ) of intermediate index is based on a mixture between, on the one hand, silicon oxide and, on the other hand, at least one metal oxide, chosen from tin oxide, zinc oxide and titanium oxide, or is based on a silicon oxynitride or oxycarbide and/or on aluminium oxynitride.  
     
     
         11 . Substrate ( 6 ) according to one of the preceding claims, characterized in that the high-index first layer ( 1 ) and/or the high-index third layer ( 3 ) are based on one or more metal oxides chosen from zinc oxide, tin oxide, zirconium oxide or the zinc-tin mixed oxide, or based on one or more nitrides chosen from silicon nitride and/or aluminium nitride.  
     
     
         12 . Substrate ( 6 ) according to one of the preceding claims, characterized in that the high-index first layer ( 1 ) and/or the high-index third layer ( 3 ) consist of a superposition of several high-index layers, especially of a superposition of two layers such as SnO 2 /Si 3 N 4  or Si 3 N 4 /SnO 2 .  
     
     
         13 . Substrate ( 6 ) according to one of the preceding claims, characterized in that the low-index second layer ( 2 ) and/or the low-index fourth layer ( 4 ) are based on silicon oxide, silicon oxynitride and/or oxycarbide or on a mixed silicon-aluminium oxide.  
     
     
         14 . Substrate ( 6 ) according to one of the preceding claims, characterized in that the said substrate is made of clear or extra-clear glass, and is preferably toughened.  
     
     
         15 . Substrate ( 6 ) according to one of the preceding claims, characterized in that the multilayer antireflection film (A) uses, at least for its high-index third layer, silicon nitride or aluminium nitride so that it is capable of undergoing a heat treatment of the toughening or annealing type.  
     
     
         16 . Substrate ( 6 ) according to one of the preceding claims, characterized in that the multilayer film (A) comprises the following sequence of layers: 
 SnO 2  or Si 3 N 4 /SiO 2 /SnO 2  or Si 3 N 4 /SiO 2  or SiAlO.    
     
     
         17 . Substrate ( 6 ) according to one of  claims 1  to  15 , characterized in that the multilayer film (A) comprises the following sequence of layers: 
 SiON/Si 3 N 4  or SnO 2 /SiO 2  or SiAlO.  
 
     
     
         18 . Substrate ( 6 ) according to one of the preceding claims, characterized in that it has a transmission integrated over a wavelength range between 400 and 1100 nm of at least 90%.  
     
     
         19 . Use of the substrate ( 6 ) according to one of the preceding claims as the external transparent substrate of solar modules ( 10 ) comprising a plurality of solar cells ( 9 ) of the Si or CIS type.  
     
     
         20 . Solar module ( 10 ) comprising a plurality of solar cells ( 9 ) of the Si, CIS, CdTe, a-Si, GaAs or GalnP type, characterized in that it has the substrate ( 6 ) according to one of  claims 1  to  18  as the external substrate.  
     
     
         21 . Solar module ( 10 ) according to  claim 20 , characterized in that its efficiency, expressed in terms of integrated current density, is increased by at least 1, 1.5 or 2% over a module using an external substrate not having the multilayer antireflection film (A).  
     
     
         22 . Solar module ( 10 ) according to either of claims  20  and  21 , characterized in that it comprises two glass substrates ( 6 ,  8 ), the solar cells ( 9 ) being placed in the inter-glass space into which a curable polymer ( 7 ) is poured.  
     
     
         23 . Process for obtaining the substrate ( 6 ) according to one of  claims 1  to  18 , characterized in that the multilayer antireflection film (A) is deposited by sputtering.