SEMI International Standards
Standards New Activity Report Form (SNARF)
Date Prepared: 11/01/2024Revised (if Applicable):

Document Number: 7314
SNARF for: New Standard: Specification for Property Requirements of Finger Pastes for TOPCon Cell with Laser Assisted Firing Process

Originating Global Technical Committee: Photovoltaic
Originating TC Chapter: China
Task Force (TF) in which work is to be carried out: Crystalline Silicon Solar Cell Task Force
Note: If a new task force is needed, also submit a task force organization form (TFOF)

___________________________________________________________________________
1. Rationale:
a. Describe the need or problem addressed by this activity.
(Indicate the customer, what benefits they will receive, and if possible, quantify the impact on the return on investment [ROI] if the Document is implemented.)
TOPcon Cell with laser assisted firing process has been adopted by almost all PV Cell manufacturers. Unlike PERC Cell or even TOPcon cell without laser assisted firing process, Some specific pastes properties may lead to the TOPCon cell issues currently bothering the PV industry, such as higher CTM loss of module, more severe acetic acid degradation, darker edge (EL/PL defects) , and finger peeling off, etc.

An unstable contact phenomenon was found, when both laser assisted firing processed and Non laser processed TOPCon cells went through thermal and light annealing in Gonda Lab. Laser assisted firing processed TOPCon cells were made with various pastes of different glass compositions. Non laser processed cells , using traditional aluminum contented silver pastes as BSL ，has little FF loss after the annealing. Some laser assisted firing processed cells with 'good' glass chemistry also show little degradation. But some cells with 'bad' glass chemistry show significant efficiency degradation, some can be more than 80%, leading to a fully dark EL images. This annealing treatment was performed by a belt light Injection furnace with a regular settings by PV production facilities. If annealed cells go through laser assisted firing processes again, Eta, FF, and Rs will recover to regular level. We did cycles of laser assisted firing process and annealing on same wafers in numerical order. As show in the attached figure. 1,3,5 on the X-axis corre- sponds to the laser assisted firing steps, and 2, 4 corresponds to the annealing steps. There is a significant difference in term of the degradation of Eta, FF, Rs for Paste A, B, C, D, E, F, G. Paste G shows best stability while Paste B shows worst stability.

Two major thermal process steps for TOPcon cells to module are soldering and lamination. Normal tabbing and stringing process needs temperature from 180 to 350 degree Celsius with 1-1.5 seconds contact. Lamination processing temperature of various module polymer is from 80 to 170 degree Celsius, and time is from 8 to 50 minutes, depends on different encapsulation materials. this thermal history may impact the metal contact stability of TOPcon cells with laser assisted firing on the same way as the experiment discussed above.
It is rational to provide a similar heat history or even harsh conditions in preventative tests to screen out risky pastes for TOPCon cells in advance. We propose to anneal the laser assisted firing processed cell by belt light injection furnace with a regular settings of solar cell facilities, which is about 400-600 degree Celsius at peak temperature, total duration time above 300 degree Celsius is around 10-20 seconds. We believe such test can effectively differentiate the TOPCon paste performance stability. Efficiency loss after the treatment should be as low as possible.
We also propose to list acetic acid resistance test results in the data sheet of pastes, refer to latest version of semi acetic resistance test standard. SEMI PV79-0818, Test method for exposure durability of photovoltaic (PV) cells to acetic acid vapor.


b. Estimate effect on industry.
2: Major effect on an industry sector - identify the relevant sector
Sector or Company Information: Cell, Module

c. Estimate technical difficulty of the activity.
II: Some Difficulty - Disagreements on known requirements exist but developing consensus is possible

___________________________________________________________________________
2. Scope:
a: Describe the technical areas to be covered or addressed by this Document development activity. For Subordinate Standards, list common concepts or criteria that the Subordinate Standard inherits from the Primary Standard, as well as differences from the Primary Standard:
This file is to propose two additional paste related performance information including post annealing degradation and acetic acid resistance on suppliers COA or data sheets for TOPCon cell with laser assisted firing process.
Post annealing Test:
Annealing Equipment is belt light Injection furnace.
400-600 degree Celsius at peak setting temperature, total duration time above 300 degree Celsius is around 10-20 seconds.
Test IV curve and EL for as-annealed solar cells.
Standard: Eta degardation <2%

b: Expected result of activity
New Standard or Safety Guideline (including replacement of an existing Standard or Safety Guideline)

For a new Subordinate Standard, identify the Primary Standard here:




For Standards, identify the Standard Subtype below:
Specification

Miscellaneous (describe below):

___________________________________________________________________________
3. Projected Timetable for Completion:

a: General Milestones
a. Activity Start: 11/01/2024b. 1st Draft by: 11/01/2025
c. (Optional) Informational Ballot by: d. Letter Ballot by: 12/01/2025
e. TC Chapter Approval By:04/01/2026

_____________________________________________________________________________
4. Liaisons with other Global Technical Committees/TC Chapters/Subcommittees/TFs:
a. List SEMI global technical committees, TC Chapters, subcommittees, or task forces in your or other Regions/Locales that should be kept informed regarding the progress of this activity. (Refer to SEMI Standards organization charts and global technical committee charters and scopes as needed.)


b. List any planned Type I Liaisons with external nonprofit organizations (e.g., SDO) that should receive Draft Documents from Standards staff for feedback during this activity and be notified when the Letter Ballot is issued (refer to Procedure Manual § 7):


c. Intercommittee Ballots:
will be issued – identify the recipient global technical committee(s):

Identify the recipient global technical committee(s):
Photovoltaic (PV) - Materials
___________________________________________________________________________
5. Safety Considerations:
The resulting document is expected:
NOT to be a Safety Guideline

NOTE FOR "to be a Safety Guideline": When all safety-related information is removed from the Document, the Document is NOT technically sound and complete - Refer to Section 15.1 of the Regulations for special procedures to be followed.

NOTE FOR "NOT to be a Safety Guideline": When all safety-related information is removed from the Document, the Document is still technically sound and complete.

___________________________________________________________________________
6. Intellectual Property Considerations:
Note: Both a: and b: below should be checked for Revision of existing Standard(s) and Safety Guideline(s).

a. For a new Standard or Safety Guideline and for any part to be modified or added in a Revision of published Standards and Safety Guidelines:
the use of patented technology is NOT required.

If "patented technology is intended to be included in the proposed Standard(s) or Safety Guideline(s) " is selected above, then also check one:


b. For Revision, Reapproval, Reinstatement, or Withdrawal of existing Standard(s) and Safety Guideline(s):


c. The body of the Document and any Appendices, Complementary Files, Related Information sections, or Various Materials that may or may not be a part of the Document by reference:
the incorporation of Copyrighted Item will NOT be required



NOTE FOR ‘the use of patented technology or the incorporation of Copyrighted Item(s) is NOT required’: If in the course of developing the Document, it is determined that the use of patented technology or Copyrighted Item(s) is necessary for the Document, the provisions of Regulations § 16 must be followed.

NOTE FOR ’will incorporate Copyrighted Item’: A copyright release letter must be obtained from the copyright owner prior to publication.

___________________________________________________________________________
7. Comments, Special Circumstances:
None.

__________________________________________________________________________
8. TC Member Review:
took place between (put dates below ) before approval at the TC Chapter Meeting, or, took place between (put dates below) before approval by the GCS, or

Member Review Start Date; 10/29/2024
Member Review End Date: 11/11/2024

NOTE FOR ‘TC Member Review’ is required by the Regulations for a period of at least two weeks
before approval of a new, or a major revision of an existing, Standard or Safety Guideline. (Refer to Regulations ¶ 8.2.1)
__________________________________________________________________________

9. SNARF Approval Dates:
TC Chapter or GCS11/20/2024
Recorded in TC Minutes

__________________________________________________________________________

10. SNARF Extension Dates:
TC Chapter Extension Granted on
Extension Expires on