Active area: The surface area of the photovoltaic module responsible for the conversion of light into electricity Adhesive: A material used to bond two surfaces together Amorphous silicon cell (a-Si): A classification of thin-film photovoltaic cells composed of noncrystalline silicon that lacks long-range order and uniform lattice structure; typical Eg = 1.7 eV Antireflective coating: Typically an inorganic coating formulated to decrease the reflection and increase the transmission of specific wavelengths of light

Backsheet: A material typically composed of a polymer used as a primary barrier to the backside of a photovoltaic module Balance of Systems (BOS): Components of the installation used to mount the array to the roof and electrically connect it to the home or business

Band gap (Eg): The energy difference between the valence and conduc­tion bands of a semiconductor material, more commonly referred to as the light energy required for a photovoltaic module to generate energy

Cadmium telluride (CdTe): A thin-film photovoltaic cell composed of a semiconductor constructed of the elements of cadmium and tellu­rium; typical Eg = 1.44 eV

Casting: Common processing technique used for elastomers and ther­mosets; an enclosure is used to give the polymer shape, and it is removed after the cure reaction is complete Cell degradation: Chemical and physical processes that decrease the photo­voltaic cell’s electrical performance over time Cell interconnects: Electrical connections between cells Cell string: A series of cells connected together in order to increase electri­cal output

Circular Fresnel lens: Visually appears similar to a planar Fresnel lens but focuses light onto a spot

Compression: A mode of mechanical deformation defined by pressing the specimen between two plates

Concentrated photovoltaics: The use of mirrors, lenses, or both to con­centrate light on a small area of photovoltaic cells and generate electricity

Copper indium diselenide (CIS): A thin-film photovoltaic cell made from a semiconductor composed of the elements copper, indium, and sele­nium; typical Eg = 1.04 eV

Copper indium gallium diselenide (CIGS): A thin-film photovoltaic cell made from a semiconductor composed of the elements of copper, indium, gallium, and selenium; typical Eg = 1.67 eV

Dielectric material: Electrical insulator that creates charge separation when an electric field is applied

Dielectric strength: The minimum electric field that causes polymeric breakdown

Directional hemispherical reflectance: The amount of reflected light from a surface when only irradiated with direct light

Elastic modulus: The slope of the stress versus strain curve in the elastic deformation region

Elastomer: A classification of polymers known for their rubbery mechani­cal behavior and chemical cross-links

Electrical insulator: A material used to separate and stabilize electrical charges

Electromagnetic spectrum: Categorization of the various wavelengths of electromagnetic radiation, also known as the light spectrum

Encapsulant: An intermittent polymer layer used to encase the photovoltaic cells in a photovoltaic module

Engineering strain: Change in length divided by the initial length

Engineering stress: Deformation force divided by the specimen’s initial area

Ethylene vinyl acetate copolymer (EVA): A copolymer composed of ethyl­ene and vinyl acetate monomers

Fill factor: The peak maximum power divided by the power that would be generated if the device could simultaneously produce at open circuit voltage and short circuit current

Fluorinated polyolefin: A thermoplastic polymer with at least one fluorine atom in its hydrocarbon chain

Free radical: A highly reactive chemical species with an unpaired electron in its atomic orbital

Grid lines: Electrical contacts on photovoltaic cells

Hydrolytic degradation: A chemical mechanism requiring the presence of water which changes the polymer’s chemical composition and phys­ical properties

Injection molding: A method of polymer processing used to convert poly­mer pellets into a new shape. It involves both heat and pressure created by a reciprocating screw and requires the molten poly­mer to be injected into a mold carved into the customer’s desired shape.

Insolation: Electromagnetic radiation on an area in a specified geographic location, time of day, and angle of orientation to the sun

Inverter: Electrical components required to covert the panel’s direct current (DC) to the alternating current (AC) output required by the home or business outlets

Ionomer: A classification of polymers that have a pendant ionic group along the backbone of the polymer chain

Irradiance: The power of the radiant electromagnetic light incident on an area per wavelength of light

Junction box: A container used to house electrical wires and connections Lamination: A processing technique used in photovoltaic packaging requir­ing heat and pressure to melt and encapsulate the photovoltaic cells Lap shear test: An adhesive test that requires pulling two substrates simul­taneously in opposite directions

Mechanical strength: The peak stress a specimen experiences before it breaks

Mechanical toughness: A material’s resistance to fracture when under stress

Mole: A unit of measure equivalent to Avogadro’s number (6.022137 x 1023) Multijunction cell: A single solar cell composed of multiple thin-film semi­conductor chemistries

Open circuit voltage: The voltage at zero current

Organic cell: A photovoltaic cell composed of polymers responsible for con­verting light into electricity, also known as a polymeric photovoltaic cell

Oxidative degradation: A chemical mechanism requiring the presence of oxygen that alters both the polymer’s chemical composition and its physical properties

Packaging factor: The effect of the packaging on the maximum power pro­duced by the photovoltaic cells

Peak maximum power: The maximum power produced on a voltage-cur­rent curve of a photovoltaic cell or module Peel test: An adhesive test that requires pulling one substrate while holding the second stationary. The direction of force is either 90o or 180o rela­tive to the stationary substrate.

Perfectly competitive market: A market described by no barriers to entry or exit, a high quantity of suppliers, and each supplier sells a homog­enous product with no ability to set market prices Photoelectric effect: The phenomenon of converting light into electricity; specifically, the active material emits electrons due to incident light rays

Photovoltaic array: A group of electrically connected photovoltaic modules Photovoltaic cell: Smallest division of a photovoltaic array capable of gen­erating power, typically composed of a semiconductor material that converts light into electricity

Photovoltaic module: A series of connected and encapsulated photovoltaic cells representing the smallest unit of energy generation available for consumer purchase, also known as a photovoltaic panel Photovoltaic thermal energy: Harnessing light energy to generate ther­mal energy; high-temperature collectors use parabolic mirrors to

concentrate light on a tube of heat transfer fluid used to power a turbine and generate electricity, also known as solar thermal Planar Fresnel lens: A type of Fresnel lens that focuses light into a beam Polar molecule: A molecule with a separation of partial charges into a slightly positive region and slightly negative region of the molecule Polyacetal: A classification of thermoplastic polymers with an acetal group in the chain and synthesized from monomers with an aldehyde or ketone functional group

Polyacrylates: A classification of thermoplastic polymers known for their optical transparency and mechanical strength and synthesized from monomers with an acryl group, also called acrylics, and polymethyl­methacrylate is one example

Polycarbonate: A thermoplastic polymer with carbonate groups in the polymer backbone and composed of the monomers bisphenol A and phosgene

Polycrystalline silicon photovoltaic cell: A type of crystalline silicon pho­tovoltaic cell composed of multiple silicon crystals characterized by multiple grain boundaries

Polyene: A polymer with multiple carbon double bonds in its backbone Polyester: A classification of thermoplastic polymers with an ester group in the chain; polyethylene terephthalate is one example Polyethylene naphthalate: A type of polyester known for its barrier proper­ties synthesized from the monomers ethylene glycol and naphtha­lene dicarboxylic acids

Polyethylene terephthalate (PET): A type of thermoplastic polymer with an ester linkage in its backbone and composed from ethylene glycol and terephthalic acid monomers

Polylactic acid: A type of biodegradable polyester derived from corn starch Polymer: A large, long molecular chain

Polymer fines: Thin slivers of polymeric pellets known to have static attrac­tion to the parts of an injection molding machine resulting in sliver decomposition and part discoloration

Polymer grade: A specific proprietary formulation provided by a manufac­turer. It includes the polymer chains and additives.

Polymer laminate: A combination of polymeric layers, metallic layers, or both adhered together to form a single material structure Polymer processing: The study and methodology of converting a polymer from one shape into another

Polyolefin: A thermoplastic composed of olefin monomers (CnH2n)

Potting: A processing technique used with elastomers and thermosets—an enclosure is used to give the polymer shape, and it is left in place after the cure reaction is complete

Quantum efficiency curve: A curve that depicts the ratio of the total amount of electrons generated from the photovoltaic cell divided by the num­ber of incident photons for each incident wavelength of light

Rheology: The study of material flow

Secant modulus: The slope, typically reported in pascal, of a line connect­ing the origin and a point on the stress-strain curve Semiconductor: A chemistry that can conduct electrons under certain cir­cumstances; the chemistry is typically doped with impurities to form electron acceptors (p-type) and electron donors (n-type)

Short circuit current: The current produced when there is zero voltage Silicone: An elastomeric polymer composed of silicon and oxygen atoms in the backbone of the chain

Single crystalline silicon photovoltaic cell: The most common type of crys­talline silicon photovoltaic cell composed of a single silicon crystal characterized by one long-range, uniform lattice structure with no grain boundaries; typical Eg = 1.1 eV

Single junction cell: A single cell composed of one semiconductor chemistry

Solar reflectance: The percentage of sunlight reflected from a surface, also known as albedo and measured in a scale from 0 to 1, with 1 indicating a 100% reflectance

Strain to break: The strain when the specimen macroscopically breaks Superstrate: A material, typically glass, that is the top surface of the photovol­taic module

Tensile: A mode of deformation commonly used in bulk polymer mechani­cal testing described as pulling the same substrate simultaneously in opposite directions

Thermoplastic: A classification of polymers known for their high modulus and irreversible yield during deformation, also known as plastics Thermoplastic elastomer: A classification of polymers which combines the rubbery properties of an elastomer and the thermoplastic’s ability to flow at elevated temperature

Thin-film cells: A classification of photovoltaic cells denoted by the thin deposition (between a few nanometers and a few microns) of semi­conductor material required to generate electricity from sunlight Ultraviolet (UV) degradation: A chemical mechanism stimulated by ultra­violet (UV) radiation that causes a change in the polymer’s chemical composition and physical properties

Ultraviolet-Visible (UV-Vis) spectrum: The transmission or absorbance of electromagnetic radiation by a substrate over the visible and ultra­violet wavelengths of the electromagnetic spectrum Viscosity: The measure of a polymer’s resistance to flow at a specified tem­perature and pressure while under shear or tensile stress

[1] Ackart, W. B.; Camp, R. L.; Wheelwright, W. L.; Byck, J. S. 2004. Antimicrobial Polymers. Journal of Biomedical Materials Research 9: 55-68.


[3] Ezrin, Myer. 1996. Plastics Failure Guide: Cause and Prevention. New York: Nahser.

[4] DuPont. 2010. DuPont Rynite® PET Technical Data Sheet. http://plastics. dupont. com/

[5] BP Solar. 2010. History. www. bp. com

[6] Wohlgemuth, J. H. 2003. Long Term Photovoltaic Module Reliability. NCPV and Solar Program Review Meeting NREL/CD-520-33586 179-182.

[7] Gilman, J. W.; Schlitzer, D. S.; Lichtenhan, J. D. 1996. Low Earth Orbit Resistant Siloxane Copolymers Journal of Applied Polymer Science 60: 591.

[8] Chopra, K.; Das, S. 1983 Thin Film Solar Cells. New York: Plenum Press.

[9] Smith, A. L. 1991. The Analytical Chemistry of Silicones. New York: John Wiley & Sons.

[10] Kimber, A.; Mitchell, L.; Nogradi, S.; Wenger, H. 2006. The Effect of Soiling on Large Grid-Connected Photovoltaic Systems in California and the Southwest Region of the United States. Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, 2: 2391-2395.


[12] Sawyer, R. F.; Pitz, W. J. September 28, 1982. Assessment of the Impact of Light Duty Diesel Vehicles on Soiling in California. Agreement A2-064-32. www. arb.

ca. gov

Updated: August 23, 2015 — 11:33 am