Apparatus For Reduction of Solar Cell LID

Abstract

Reduction of solar wafer LID by exposure to continuous or intermittent High-Intensity full-spectrum Light Radiation, HILR, by an Enhanced Light Source, ELS, producing 3-10 Sols, optionally in the presence of forming gas or/and heating to within the range of from 100° C.-300° C. HILR is provided by ELS modules for stand-alone bulk/continuous processing, or integrated in wafer processing lines in a High-Intensity Light Zone, HILZ, downstream of a wafer firing furnace. A finger drive wafer transport provides continuous shadowless processing speeds of 200-400 inches/minute in the integrated furnace/HILZ. Wafer dwell time in the peak-firing zone is 1-2 seconds. Wafers are immediately cooled from peak firing temperature of 850° C.-1050° C. in a quench zone ahead of the HILZ-ELS modules. Dwell in the HILZ is from about 10 sec to 5 minutes, preferably 10-180 seconds. Intermittent HILR exposure is produced by electronic control, a mask, rotating slotted plate or moving belt.

1 . Apparatus for treating Si wafers for solar cells to reduce Light Induced Degradation (LID) resulting from in-use operation of said solar cell during exposure to sunlight, comprising in operative combination:
 a. means for retaining a plurality of Si wafers in a treatment zone in a generally horizontal plane, each of said Si wafers having a top and a bottom surface oriented with said top surface facing upwardly while being retained in said horizontal plane of said treatment zone;   b. means for transporting said plurality of Si wafers continuously and sequentially in a linear direction through said treatment zone in a generally horizontal path;   c. at least one Light Emitting Plasma (LEP) lamp outputting high-intensity full-spectrum light radiation disposed in said treatment zone above said top surface of said Si wafers to expose said Si wafer top surfaces to an amount of said radiation of from 3 Sols to 10 Sols for a time period of from 10 seconds to 5 minutes sufficient to reduce LID that would otherwise be exhibited by said wafer; and   d. Infrared Radiation (IR) lamps disposed above said Si wafer top surfaces to heat said Si wafers during exposure to said full-spectrum light radiation, said IR lamps including means for controlling said heating separately from said LEP lamps to maintain a temperature of said wafers in a range of 100° C.-300° C.   
     
     
         2 . An apparatus as in  claim 1  wherein said means for retaining said plurality of Si wafers in a generally horizontal plane comprises a conveyor system for controlled continuous transport of said plurality of Si wafers sequentially through said zone of treatment of said wafers for exposure by said LEP and IR lamps for said time period. 
     
     
         3 . (canceled) 
     
     
         4 . An apparatus as in  claim 2  wherein a plurality of said LEP lamps are arrayed in a linear sequence to define said treatment zone for continuous processing. 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . An apparatus as in  claim 1  which includes means for intermittently exposing said wafer to radiation from said LEP lamps. 
     
     
         8 . An apparatus as in  claim 4  which includes means for intermittently exposing said wafer to radiation from said LEP lamps. 
     
     
         9 . An apparatus as in  claim 8  wherein said means for intermittently exposing said wafers to radiation from said LEP lamps comprises a slotted mask interposed between said LEP lamp and said wafers so that as said wafers traverse below said slotted mask during transport through said treatment zone, alternating bands of LEP light radiation and shadow traverse the top surface of said wafers. 
     
     
         10 . Apparatus as in  claim 9  which includes a wafer firing furnace, selected from a diffusion furnace and a metallization furnace, disposed upstream of, and connected to said HILR treatment zone, said wafer firing furnace includes a wafer conveyor system, and said wafer firing furnace conveyor system is extended into and functions as said HILR treatment zone conveyor. 
     
     
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