# Presentation: 504267

## National CdTe Team Meeting 

- National CdTe Team Meeting
- May 5 and May 6 2005
- W. S. Sampath, R. Albert Enzenroth, and  Kurt L. Barth
- Materials Engineering Laboratory,
- Colorado State University, Fort Collins, Colorado

## Our Approach to PV Manufacturing  

**Our Approach to PV Manufacturing  **

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**Process Flow and Pilot System Schematic for Semiconductor Fabrication**
- (1) belt conveyor, (2) glass substrate, (3) air to vacuum to air (AVA) seal,
- (4) Vacuum chamber, (5) heating module, (6) CdS deposition, (7) CdTe deposition, (8) CdCl2 deposition and heat treatment, (9) CdCl2 annealing and stripping,
- (10) back contact formation, (11) contact annealing, (12) AVA seal,
- (13) cell ready for EB 003 and Electrodag 550 application (C and Ni in polymer binder)
**Two Systems**: (a) Pilot system for 3” X 3” substrates , and
-                          (b) Production prototype for 16” X 16” substrates

## Nine Hour Run with Same Source charge

- Voc and Jsc during 9 hour processing with the same source charge
- for CdS, CdTe and CdCl2.These devices had no back contact (no Cu doping)
- but had the back electrode (sprayed C and Ni films)

## Nine Hour Run with Same

- operation with same source charge CdS, CdTe and CdCl2 . The source
- charge materials suitable for industrial processing.

**Nine Hour Run with Same**
**Source charge**

## Nine Hour Run with Same Source charge

**Nine Hour Run with Same Source charge**

- Average Efficiency Vs. Accelerated Stress Time for Three Groups of Cells.
- Stress conditions are: 65 C, 1 sun, 5 hrs ON/ 3 hrs off.
**Demonstrates Reproducibility of Stability**

## Materials for Encapsulation

***All our stress studies, to date, performed in desiccated air***
***Most polymers saturate with moisture in time duration less than the desired life of 20+ years.***
***Can edge seal with desiccant keep moisture away from the devices for 20+ years? Modeled moisture transmission through Truseal solar edge tape.***

## Moisture Transmission through Truseal Edge Tape.

***Assume disc is at 65C, exposed to saturated humidity (187 torr vapor pressure for water), disc=100 sq. in., 0.050” thickness saturated. ***
***  ******Water transmission through 0.050” thickness= 0.084 g/day (data from Truseal)***
*** ******Time to saturate next 0.050”  thickness = 43 days (Truseal data)***
*** ******Time to saturate the next 0.050” thickness=86 days***
*** ******Summing this way (43+86+129+172+.....), time to saturate 1” thickness= 22.3 years, at 65C, one side exposed to 187 torr water.***
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## Interconnection Studies

*** ***
***For scribing the TO:F, the Nd:YAG laser has been found to be suitable. The CdS/CdTe films deposited on scribed surfaces provide shunt resistance***
*** ******2. Mechanical scribing of  CdS/CdTe layer has shown low contact resistance of less then 1 ohm for 1 cm. Nd:YAG laser (flash lamp) scribing from film side, have not resulted in a clean scribe of CdS/CdTe. More experiments on laser scribing underway.***
*** ******3. For the isolation of the back electrode, abrasive blasting through a mask will be utilized. ***

## 2 MW/Yr. System Development

*** ***

## 2 MW/Yr. System Development

***Funded by DOE-EERE and cost shared by NSC***
*** ******Loadlocks designed, constructed and partially tested***
*** ******Large area sources tested for 78 hours, thermal uniformity +/- 1.5 C at 400C***
*** ******NSC designing and constructing system for metallization***

## Future Work

*** ******1. Process (vapor flux, substrate temperature, residual gas almost fully defined) except for the back contact process. Pilot system being extended for  precise definition of back contact process.***
*** ******2. Transfer the process defined above to production prototype and demonstrate semiconductor processes at 2 MW/Yr. level by 12/06.***
*** ******3. Demonstrate interconnection and encapsulation and provide modules for beta testing.***
*** ******4. Independent evaluation by outside consultants of the cost (capital and manufacturing) for the DOE project.***