Feedback for buffer layer deposition

Abstract

Improved methods and apparatus for forming thin film layers of chalcogenide on a substrate web. According to the present teachings, a feedback control system may be employed to measure one or more properties of the web and/or the chalcogenide layer, and to adjust one or more parameters of the system or buffer layer deposition method in response to the measurement.

1 . A system for depositing a chalcogenide buffer layer onto a flexible substrate, comprising:
 a transport mechanism configured to transport a web of thin film photovoltaic substrate material through a deposition region in a longitudinal direction;   a dispensing mechanism configured to dispense a metal-containing solution and a chalcogen-containing solution onto the web in the deposition region; and   a feedback mechanism including first and second sensors configured to measure at least one property of a chalcogenide buffer layer formed on the web through chemical combination of the dispensed solutions;   wherein the feedback mechanism is configured to adjust at least one parameter of the system in response to the at least one measured property.   
   
   
       2 . The system of  claim 1 , wherein the at least one property is selected from the group consisting of: thickness; uniformity across a transverse dimension of the web; color; a ratio of red light intensity to green+blue light intensity; photon absorption; and intensity of reflected light. 
   
   
       3 . The system of  claim 1 , wherein the first sensor is a first camera for digitally capturing images of the web prior to formation of the chalcogenide buffer layer, the second sensor is a second camera for digitally capturing images of the web after formation of the chalcogenide buffer layer, and evaluating the at least one property of the chalcogenide buffer layer includes comparing an image captured by the second camera with an image captured by the first camera. 
   
   
       4 . The system of  claim 1 , wherein the at least one parameter is selected from the group consisting of: speed of the web through the deposition region; concentration of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web; average temperature of the web in the deposition region; height of at least one edge portion of the web; temperature of the metal-containing solution; a dispensing rate of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web; and longitudinal slope of the web. 
   
   
       5 . The system of  claim 1 , wherein the at least one property is a ratio of a color of light captured by the first sensor to a color of light captured by the second sensor. 
   
   
       6 . A system for depositing a chalcogenide buffer layer onto a flexible substrate, comprising:
 a transport mechanism configured to deposit a web of thin film photovoltaic substrate material through a deposition region in a longitudinal direction;   a dispensing mechanism configured to dispense a metal-containing solution and a chalcogen-containing solution onto the web in the deposition region;   a measuring instrument configured to collect data relating to at least one property of a chalcogenide buffer layer formed on the web through chemical combination of the dispensed solutions; and   a digital processor configured to automatically determine a value of the at least one property from the data collected by the measuring instrument, and to automatically adjust at least one parameter of the system in response to the value of the at least one property.   
   
   
       7 . The system of  claim 6 , wherein the at least one property is selected from the group consisting of: thickness; uniformity across a transverse dimension of the web; color; a ratio of red light intensity to green+blue light intensity; photon absorption; and intensity of reflected light. 
   
   
       8 . The system of  claim 6 , wherein the at least one parameter is selected from the group consisting of: speed of the web through the deposition region; concentration of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web; average temperature of the web in the deposition region; height of at least one edge portion of the web; temperature of the metal-containing solution; a dispensing rate of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web; and longitudinal slope of the web. 
   
   
       9 . A system for depositing a chalcogenide buffer layer onto a flexible substrate, comprising:
 a transport mechanism including a plurality of rollers disposed within a deposition region and configured to transport a web of thin film photovoltaic substrate material through the deposition region in a longitudinal direction;   a dispensing mechanism configured to dispense a metal-containing solution and a chalcogen-containing solution onto the web in the deposition region; and   a feedback mechanism configured to measure at least one property of a chalcogenide buffer layer formed on the web through chemical combination of the dispensed solutions, and to adjust at least one parameter of the system in response to the at least one measured property.   
   
   
       10 . The system of  claim 9 , wherein the at least one property is selected from the group consisting of: thickness; uniformity across a transverse dimension of the web; color; a ratio of red light intensity to green+blue light intensity; photon absorption; and intensity of reflected light. 
   
   
       11 . The system of  claim 9 , wherein the at least one parameter is selected from the group consisting of: speed of the web through the deposition region; concentration of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web; average temperature of the web in the deposition region; height of at least one edge portion of the web; temperature of the metal-containing solution; a dispensing rate of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web; and longitudinal slope of the web. 
   
   
       12 . A method of depositing a chalcogenide buffer layer onto a flexible substrate, comprising:
 transporting a web of thin film photovoltaic substrate material through a deposition region in a longitudinal direction;   dispensing a metal-containing solution and a chalcogen-containing solution onto the web in the deposition region;   measuring a value of at least one property of a chalcogenide buffer layer formed on the web through chemical combination of the dispensed solutions; and   adjusting at least one parameter in response to the value of the at least one measured property;   wherein the at least one property is selected from the group consisting of: thickness; uniformity across a transverse dimension of the web; photon absorption; and intensity of reflected light.   
   
   
       13 . The method of  claim 12 , wherein measuring the value includes obtaining a first image of the web prior to dispensing the solutions onto the web, obtaining a second image of the web after formation of the chalcogenide buffer layer, and determining the value from the first and second images using a digital processor. 
   
   
       14 . The method of  claim 12 , wherein the at least one parameter is speed of the web through the deposition region. 
   
   
       15 . The method of  claim 12 , wherein the at least one parameter is concentration of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web. 
   
   
       16 . The method of  claim 12 , wherein the at least one parameter is average temperature of the web in the deposition region. 
   
   
       17 . The method of  claim 12 , wherein the at least one parameter is height of at least one edge portion of the web. 
   
   
       18 . The method of  claim 12 , wherein the at least one parameter is temperature of the metal-containing solution. 
   
   
       19 . The method of  claim 12 , wherein the at least one parameter is a dispensing rate of at least one of the group consisting of the metal-containing solution, the chalcogen-containing solution, and a chemical complexant dispensed onto the web. 
   
   
       20 . The method of  claim 12 , wherein the at least one parameter is longitudinal slope of the web. 
   
   
       21 . The method of  claim 12 , wherein the feedback mechanism includes first and second cameras for digitally capturing images of the web, and the at least one property is a ratio of a first color intensity to a second color intensity. 
   
   
       22 . The method of  claim 12 , wherein the feedback mechanism includes first and second cameras for digitally capturing images of the web, and the property is intensity of reflected light.