SEMI International Standards
SEMI New Activity Report Form (SNARF)

Activity Number: 4921
SNARF for: New Standard: Guide for Specifying BRDF Metrics to Monitor the Surface Roughness and Texture of PV Materials

Originating Global Technical Committee: Photovoltaic
Originating Technical Committee Region: North America
Task Force in which work is to be carried out: PV Electrical & Optical Properties Measurements Task Force

1. Rationale: Many surfaces used in the photovoltaic industry are textured in order to optimize light absorption and maximize cell efficiency. The amount and nature of texture required differs with material and cell design; however, in general these surfaces are not optically smooth – that is they are not mirrors. In addition, the required texture is not well defined by a single roughness, gloss or haze specification because the relative amount of low and high frequency roughness on the surface can be important. Thus two or more parameters may have to be specified. Profile measurements may provide enough information, but these are slow, vibration sensitive and expensive. Light scatter measured over a range of angles (or several angles) provides a fast, economical means to monitor texture over a range of roughness frequencies. The proposed document provides a means to specify measured scatter in BRDF units, for both lab and production settings, so that surface texture can be kept within previously determined acceptable bounds.
Rate the Estimated Effect on the Industry
1: Major effect on entire industry or on multiple important industry sectors

Rate the Estimated Technical Difficulty of the Activity
II: Some Difficulty - Disagreements on known requirements exist but developing consensus is possible

2. Scope:
a: Define the areas to be covered or addressed by this activity or document:
The proposed standard will rely on SEMI ME1392-1109 - Guide for Angle Resolved Optical Scatter Measurements on Specular or Diffuse Surfaces, which defines the calculation and measurement of bidirectional reflectance distribution function (or BRDF). The proposed document will provide a means to specify BRDF max/min limitations as a function of angle or at prescribed angles.

b: Expected result of activity
New Standard

3. Projected Timetable for Completion:
a: General Milestones
a. Activity Start: 03/01/2010b. 1st Draft by: 04/01/2010
c. Preballot by: d. Technical Ballot by: 07/12/2010
e. Committee Approval By:01/01/2011

Safety Considerations:
The resulting document is expected NOT to be a Safety Guideline

Intellectual Property Considerations:
a. In complying with the standard or safety guideline to be developed, the use of patented technology or a copyrighted item(s) is NOT required
b. The body of the standard and any appendices or related information sections will NOT include copyrighted material

Comments, Special Circumstances: None.

Approval: Activity approved by Committee/GCS on March 31, 2010