Thermal pre-treatment process for soda lime glass substrate for thin film photovoltaic materials

Abstract

A method for fabricating a thin film solar cell includes providing a soda lime glass substrate comprising a surface region, treating the surface region with one or more cleaning process including an aqueous solution to remove one or more contaminants and/or particulates, and forming a lower electrode layer overlying the surface region. The method also includes performing a thermal treatment process to remove any residual water species to substantially less than a monolayer of water species from the lower electrode layer and soda lime glass substrate. The thermal treatment process changes a temperature of the soda lime glass substrate from a first temperature to a second temperature to pre-heat the soda lime glass substrate. Additionally, the method includes transferring the soda lime glass substrate, which has been preheated, to a deposition chamber and forming a layer of photovoltaic material overlying the lower electrode layer within the deposition chamber.

What is claimed is: 
     
         1 . A method for fabricating a thin film solar cell, the method comprising:
 treating a surface region of a substrate with an aqueous;   subsequently forming a lower electrode layer including a conductive metal over the surface region;   performing a thermal treatment process on the substrate and the lower electrode layer to remove residual water species; and   forming a layer of photovoltaic material overlying the lower electrode layer.   
     
     
         2 . The method of  claim 1  wherein performing the thermal treatment process comprises thermally desorbing residual water species. 
     
     
         3 . The method of  claim 1  wherein performing the thermal treatment process comprises subjecting a plurality of infrared heaters from a backside of the substrate. 
     
     
         4 . The method of  claim 3  wherein the thermal treatment process comprises heating the substrate with the infrared heaters for less than about 250 seconds. 
     
     
         5 . The method of  claim 3  wherein the thermal treatment process comprises heating the substrate with the infrared heaters for less than about 60 seconds. 
     
     
         6 . The method of  claim 3  wherein the thermal treatment process comprises rolling the soda lime glass substrate back and forth over the plurality of infrared heaters. 
     
     
         7 . The method of  claim 1  wherein the thermal treatment process heats the substrate from a first temperature to a second temperature less than or about 170 degrees Celsius. 
     
     
         8 . The method of  claim 1  wherein the layer of photovoltaic material comprises one or more precursor layers of an absorber material. 
     
     
         9 . The method of  claim 8  wherein the one or more precursor layers comprises at least a copper layer and/or an indium layer. 
     
     
         10 . The method of  claim 1  further comprising forming a barrier layer overlying the surface region before forming the lower electrode layer. 
     
     
         11 . The method of  claim 10  wherein the barrier layer comprises a silicon dioxide layer of about 500 Angstroms or less for keeping sodium species within the soda lime glass substrate during the thermal treatment process. 
     
     
         12 . A method for fabricating a thin film solar cell, the method comprising:
 treating a surface of a substrate with an acidic solution;   forming a layer of a conductive metal directly over the surface region;   performing a thermal treatment process on the substrate having the layer of conductive material, the thermal treatment process changing a temperature of the soda lime glass substrate from a first temperature to a second temperature;   transferring the preheated substrate to a deposition chamber; and   forming a layer of photovoltaic material overlying the lower electrode layer within the deposition chamber.   
     
     
         13 . The method of  claim 12  wherein performing the thermal treatment process comprises thermally desorbing residual water species. 
     
     
         14 . The method of  claim 12  wherein performing the thermal treatment process comprises subjecting a plurality of infrared heaters from a backside of the substrate. 
     
     
         15 . The method of  claim 14  wherein the thermal treatment process comprises rolling the soda lime glass substrate back and forth over the plurality of infrared heaters. 
     
     
         16 . The method of  claim 14  wherein the thermal treatment process comprises heating the substrate with the infrared heaters for less than about 250 seconds. 
     
     
         17 . The method of  claim 14  wherein the thermal treatment process comprises heating the substrate with the infrared heaters for less than about 60 seconds. 
     
     
         18 . The method of  claim 12  wherein the thermal treatment process heats the substrate from a first temperature to a second temperature less than or about 170 degrees Celsius. 
     
     
         19 . The method of  claim 12  wherein the layer of photovoltaic material comprises one or more precursor layers of an absorber material. 
     
     
         20 . The method of  claim 19  wherein the one or more precursor layers comprises at least a copper layer and/or an indium layer.