Synthesis of nanostructured photoactive films with controlled morphology by a flame aerosol reactor

Abstract

An improved process for the preparation of nanostructured metal species-based films in a flame aerosol reactor is provided. The process comprises combusting vaporized metal precursor, vaporized fuel and vaporized oxidizer streams to form metal species-based nanoparticles in a flame that are deposited onto a temperature controlled support surface and sintered to form the metal species-based nanostructured film. Improved nanostructured photo-watersplitting cells having a sunlight to hydrogen conversion efficiency of from about 10% to about 15%, dye sensitized solar cells having a sunlight to electricity conversion efficiency of from about 10% to about 20%, and nanostructured p/n junction solar cells having a sunlight to electricity conversion of from about 10% to about 20% are provided. Each cell type comprises a nanostructured metal oxide film having continuous individual columnar structures having an average width (w) and grain size criterion (X 3 ) wherein w/10 is greater than X 3 .

1 . A nanostructured photo-watersplitting cell for the production of hydrogen, the cell comprising:
 a photoanode comprising a support and a nanostructured metal oxide film disposed on at least one surface of the support, wherein the film predominantly comprises a columnar morphology characterized as having continuous individual columnar structures oriented approximately normal to the support wherein the columnar structures have an average width, w, and a grain size criterion, X s , and wherein w/10 is greater than X s , and   a cathode comprising a counter electrode   wherein the nanostructured photo-water splitting cell has a sunlight to hydrogen conversion efficiency of from about 10% to about 15%.   
     
     
         2 . (canceled) 
     
     
         3 . The nanostructured photo-water splitting cell of  claim 1  wherein the nanostructured metal oxide comprises metal oxide particles having an average particle size of less than about 100 nanometers. 
     
     
         4 - 6 . (canceled) 
     
     
         7 . The nanostructured photo-water splitting cell of  claim 3  wherein the average particle size is less than about 20 nanometers and the nanostructure has a short range crystalline order of about 1 to about 50 nanometers. 
     
     
         8 . A nanostructured dye-sensitized solar cell comprising:
 an electron conducting layer comprising a support and a nanostructured metal oxide film disposed on at least one surface of the support, wherein the film predominantly comprises a columnar morphology characterized as having continuous individual columnar structures oriented approximately normal to the support wherein the columnar structures have an average width, w, and a grain size criterion, X s , and wherein w/10 is greater than X s ,   a light absorbing layer, and   a hole-conducting layer,   wherein the nanostructured dye-sensitized solar cell has a sunlight to electricity conversion efficiency of from about 10% to about 20%.   
     
     
         9 . (canceled) 
     
     
         10 . The nanostructured dye-sensitized solar cell of  claim 8  wherein the nanostructured metal oxide comprises metal oxide particles having an average particle size of less than about 100 nanometers. 
     
     
         11 - 13 . (canceled) 
     
     
         14 . The nanostructured dye-sensitized solar cell of  claim 10  wherein the average particle size is less than about 20 nanometers and the nanostructure has a short range crystalline order of about 1 to about 50 nanometers. 
     
     
         15 . A nanostructured p/n junction solar cell comprising:
 an n-type oxide semiconductor layer comprising a support and a nanostructured metal oxide film disposed on at least one surface of the support, wherein the film predominantly comprises a columnar morphology characterized as having continuous individual columnar structures oriented approximately normal to the support wherein the columnar structures have an average width, w, and a grain size criterion, X s , and wherein w/10 is greater than X s ,   an p-type oxide semiconductor layer comprising a support and a nanostructured metal oxide film disposed on at least one surface of the support, wherein the film predominantly comprises a columnar morphology characterized as having continuous individual columnar structures oriented approximately normal to the support wherein the columnar structures have an average width, w, and a grain size criterion, X s , and wherein w/10 is greater than X s ,   wherein the nanostructured p/n junction solar cell has a sunlight to electricity conversion of from about 10% to about 20%.   
     
     
         16 - 17 . (canceled) 
     
     
         18 . The nanostructured p/n junction solar cell of  claim 15  wherein the nanostructured metal oxide comprises metal oxide particles having an average particle size of less than about 100 nanometers. 
     
     
         19 - 21 . (canceled) 
     
     
         22 . The nanostructured p/n junction solar cell of  claim 18  wherein the average particle size is less than about 20 nanometers and the nanostructure has a short range crystalline order of about 1 to about 50 nanometers. 
     
     
         23 . A process for the preparation of a metal species-based nanostructured film in a flame aerosol reactor, the method comprising:
 introducing a vaporized metal precursor stream;   introducing a vaporized fuel stream;   introducing a vaporized oxidizer stream;   combusting the metal precursor stream, the fuel stream and the oxidizer stream in a flame to form metal species-based nanoparticles in the flame region;   depositing the metal species-based nanoparticles onto a support surface wherein the temperature of the surface is controlled; and   sintering the metal species-based nanoparticles to form the metal species-based nanostructured film.   
     
     
         24 - 25 . (canceled) 
     
     
         26 . The process of  claim 23  wherein the flame temperature is from about 1500° C. to about 3500° C. 
     
     
         27 - 32 . (canceled) 
     
     
         33 . The process of  claim 23  wherein the metal species-based nanoparticle comprises a zero valent metal. 
     
     
         34 . The process of  claim 23  wherein the nanostructure is of predominantly of columnar morphology or predominantly of granular morphology. 
     
     
         35 . The process of  claim 23  wherein the metal species-based nanoparticles have an average particle size of less than about 100 nanometers. 
     
     
         36 - 38 . (canceled) 
     
     
         39 . The process of  claim 35  wherein the average particle size is less than about 20 nanometers and the nanostructure morphology is predominantly columnar having a short range crystalline order of about 1 to about 50 nanometers. 
     
     
         40 - 46 . (canceled) 
     
     
         47 . A process for the preparation of a metal species-based nanostructured film in a flame aerosol reactor, the method comprising:
 introducing a vaporized metal precursor stream;   introducing a vaporized fuel stream;   combusting the metal precursor stream and the fuel stream in a flame to form in the flame region metal species-based nanoparticles comprising zero valent metal; and   depositing the metal species-based nanoparticles onto a support surface wherein the temperature of the surface is controlled; and   sintering the metal species-based nanoparticles to form the metal species-based nanostructured film.   
     
     
         48 - 49 . (canceled) 
     
     
         50 . The process of  claim 47  wherein the nanostructure is of predominantly of columnar morphology or predominantly of granular morphology. 
     
     
         51 . The process of  claim 47  wherein the metal species-based nanoparticles have an average particle size of less than about 100 nanometers. 
     
     
         52 - 54 . (canceled) 
     
     
         55 . The process of clam  47  wherein the nanostructure morphology is predominantly columnar having a short range crystalline order of about 1 to about 50 nanometers. 
     
     
         56 - 58 . (canceled)