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Solar Energy Glossary of Terms

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Why?

We get asked lots of questions about what does this solar term or that solar term mean. So we decided to create this page and include it in our Solar University, which strives to educate the public on solar energy.

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Glossary:

A

A-Rack
Holds glass on both sides. A shape structure configuration.
Accum
Work in Progress (WIP) Buffer
Ag
The symbol for the element gold. Aluminum and gold are used in solar cell production to conduct electricity and reflect light.
Al
The symbol for the element aluminum. Aluminum and gold are used in solar cell production to conduct electricity and reflect light.
Amorphous Semiconductor
A semiconductor material which is not entirely crystalline, having only short-range order in its structure.
A non-crystalline semiconductor material, that is cheaper than crystalline, but less efficient and slowly degrades over time. Also known as thin film.
Amorphous Silicon (a-Si)
Non-crystalline allotropic form of silicon in which the atoms are disordered from optimum crystalline positions. To compensate for the resulting “dangling bonds,” hydrogen is alloyed with silicon.
A type of silicon deposited on a variety of surfaces (rigid and flexible) with thin homogenous layers. Amorphous silicon absorbs light more effectively than crystalline silicon, so the cells can be thinner. For this reason, amorphous silicon is also known as a "thin film" photovoltaic technology.
Autoclave
Pressurized device designed to heat aqueous solutions above their boiling point to achieve sterilization. Autoclaving is used to improve adhesiveness between the PVB and glass substrates by removing trapped air.

B

Back Glass
Ensures no gridlines or visible tabs are present on the front of the cells.
Creates a uniform appearance, unrestricted by reflectance.
Balance of System (BOS)
The balance of system or BOS encompasses all components of a photovoltaic system other than the photovoltaic panels. This includes wiring, switches, support racks, an inverter, and batteries in the case of off-grid systems. In the case of free-standing systems, land is sometimes included as part of the BOS.
Bunny Suit
Special clothing worn by people working in clean rooms that reduce the amount of particles that could damage a solar module.
Bus
Electricity. A bus bar.
Bus Wire Attachment tool automatically installs the tabbing wire and the bus wire.

C

Cd-Te
Cadmium Telluride: a type of thin-film solar cell design that uses a cadmium-tellurium compound as the semiconductor layer.
Chemical Vapor Deposition
A process for depositing thin films from a chemical reaction of a vapor or gas.
CIS (CIGS)
Copper Indium Diselenide: a type of thin film solar cell material that uses a compound of copper, indium, selenium. A fourth element, gallium, may also be added to the compound (CIGS) to achieve higher performance in PV cells.
Cell
A semiconductor device that converts the energy of sunlight into electric energy. Also called photovoltaic cell.
The solar cell is the basic electrical device in solar power. Multiple cells are wired together to form modules of the needed area.
Cleanroom
The portion of the fabrication facility where modules are manufactured that is maintained virtually free of contaminants, such as dust. These rooms are strictly monitored to ensure successful manufacturing of panels.
Conductor
A substance or medium that conducts electric charge.
Crystalline Silicon (c-Si)
A generic term for solar cell technology that uses a substrate of purified silicon in a crystalline structure.
Crystalline silicon, also called wafer silicon, is a material consisting of one or more small silicon crystals. It is different from amorphous silicon, used for thin films (thin-film silicon cell).
Gray color and metallic luster increase with crystal size.
Has properties similar to glass in that it is strong, brittle, and has a tendency to chip.
CVD
Plasma-Enhanced Chemical Vapor Deposition Tool (PECVD)
Substrates are exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit.
CVD Abatement
Tool used to abate toxic gases.
CVD Pump
Tool used to pump process lines.

D

Deposition
A process used to deposit a thin layer of insulating or conductive material onto the wafer.

E

Etch
A process for removing material in a specified area through a chemical reaction.

F

Fab
A fabrication facility for manufacturing solar panels.

G

GW
Gigawatt: One thousand (1000) MW or 1 billion watts (109).
GWp
Giga Watt peak (1,000 MWp); solar industry unit for normal power.

H

HS20
Cutting liquid (glycol based).
HSEM Hand Seam Inspection
Used to round the edges and corners of the glass to reduce damage and improve factory yields.

I

Inverter
An inverter allows DC power from solar panels to supply AC power that is normally supplied from a main power source or grid electricity.

J

JBX
Junction box attachment tool installs the J-Box, solder J-Box leads, and J-Box lid used to attach PV-Instant Seal Bond line.
Junction Box
Used to protect soldered electrical connections between the output and cables.
Provide an output wiring for the solar module.

K

KG
Unit of mass: Kilogram.
The base unit of mass in the International System, equal to 1,000 grams (2.2046 pounds).
KM
Unit of Length: Kilometer
A metric unit of length equal to 1000 meters (or 0.621371 miles).
KW
Unit of Power: Kilowatt: 1,000 watts of electrical output.
An International System unit of power equal to one thousand joules per second.
Kerf Loss
Kerf loss is associated with the amount of material loss during a cutting process. In crystalline wafer production, kerf loss refers to the amount of silicon consumed as part of the wafering process and plays a vital role in determining the overall dimension, edge quality, and surface finish of a wafer.

L

LCD
Liquid Crystal Display:  A low-power flat-panel display used in many laptop computers, calculators and digital watches, made up of a liquid crystal that is sandwiched between layers of glass or plastic and becomes opaque when electric current passes through it. The contrast between the opaque and transparent areas forms visible characters.
LED
Light Emitting Diode:  A rectifying semiconductor device which converts electrical energy into electromagnetic radiation. The wavelength of the emitted radiation ranges from the near-ultraviolet to the near-infrared, that is, from about 400 to over 1500 nanometers.
Laser Scribe
Multiple lasers per system with indexing optics direct laser towards the glass at appropriate scribe separation. First Laser – removes selected semiconductor and metal electrode layers (TCO) from the substrate. Second Laser – etches a groove for the contact area for both the metal and transparent electrode (a-Si) layers. Third Laser – produces a contact area groove for both the metal and a-Si layers.

M

mm
Millimeter:  The millimeter is a unit of length in the metric system, equal to one thousandth of a meter.
mm2
One Square Millimeter: Is a unit of area in the metric system.
MW
Megawatt: A unit of power: One million watts, or 1,000 KW.
A typical large electrical generating plant can produce a thousand megawatts of electricity.
MWp
Megawatt Peak (1MWp=1,000 kilowatt peak); a measuring unit for normal power output of solar cells in the solar industry.
Micron
One-millionth of a meter, or 1,000 nanometers.
Microcrystalline
Is a crystallized substance or rock which contains small crystals that are visible through microscopic examination. i.e. Microcrystalline Silicon (µc-Si).
Microcrystalline Silicon (µc-Si)
A form of thin film silicon with very small (0.5-2 micron) grain structure intermixed with amorphous silicon. It is usually deposited in a thin layer (typically 1-3 microns) for tandem (stacked) thin film solar cells.
Module
The solar module is a packaged interconnected assembly of photovoltaic cells, also known as solar cells.
Monocrystalline Silicon
Crystalline silicon in which the wafer is cut from a single silicon crystal with a perfect crystalline lattice structure. Also used for Integrated Circuits.
Multi-Crystalline Silicon
Crystalline Silicon in which the wafer is made from silicon that has been melted and cast into blocks, creating a structure of many large silicon crystal grains.

N

O

P

PECVD
Plasma enhanced chemical vapor deposition: a glow discharge based deposition technology used to form many kinds of coatings, including both a-Si (amorphous silicon) and SiN (silicon nitride) layers for solar cells.
Percent Efficiency
% Efficiency = Electrical Energy / Sunlight Energy
Photovoltaic (PV)
PV devices convert sunlight directly to electrical current.
Relating to, or utilizing the generation of a voltage when radiant energy falls on the boundary between dissimilar substances (as two different semiconductors).
Polyvinyl Butyral (PVB)
Shock-absorbing safety interlayer in safety glazing.
Safety glazing to provide features such as solar energy control, weight reduction by eliminating one glass layer (called a bi-layer structure), head-up displays in automobiles and liquid crystal and electro-chromic devices for privacy applications.
PV
See Photovoltaic.
PVD
Physical Vapor Deposition or "sputtering" is a process by which a thin film of material is deposited on a substrate according to the following sequence of steps:
  1. Deposited material is converted into vapor by physical means.
  2. Vapor is transported across a region of low pressure from its source to the substrate.
  3. Vapor undergoes condensation on the substrate to form the thin film.
  4. A type of deposition method in which atoms are detached from a target of a certain material and then deposited on a substrate.

Q

R

S

Si
The symbol for the element Silicon. A nonmetallic element occurring extensively in the earth's crust in silica and silicates, having both an amorphous and a crystalline allotrope, and used doped or in combination with other materials in glass, semiconducting devices, concrete, brick, refractories, pottery, and silicones. 
SRU
Slurry recovery unit.
Single-Crystal Silicon
See monocrystalline silicon.
Single Junction
Single layer p-n junction diode (monocrystalline silicone c-Si).
Solar Farm
Solar power plants that generate electricity by converting solar energy to heat, to drive a thermal power plant.
System Cost
Module Cost + Balance of System.

T

Tons (t)
A unit of weight equal to 2,000 pounds (0.907 metric ton or 907.18 kilograms). Also called net ton, short ton.
Tandem Junction
Amorphous silicon and crystalline combined in thin layers, creating a layered cell.
Tandem solar cells designs use multiple light absorbing semiconducting materials to increase conversion efficiency.
TCO
See Transparent Conducting Oxide
Thin Film
Are thin material layers ranging from fractions of a nanometer to several micrometers thick.
Transparent Conducting Oxide (TCO)
Transparent Conducting Oxide: this is typically the top active layer in a solar cell and is often made of zinc oxide or tin oxide. It needs to be transparent to allow light transmission, but be electrically conducive.
In general, TCO thin films are transparent electrodes either polycrystalline or amorphous, except for single crystals which are grown epitaxially and exhibit a resistivity in an order of 10-3 Ω cm or less with an average transmittance above 80% in the visible range.

U

µm
An abbreviated form of micrometer. A unit of length equal to one millionth of a meter.

V

W

W
Unit of power: Watt: An International System unit of power equal to one joule per second.
Wire Saw
Slices mono and polycrystalline bricks into wafers.

X

Y

Z

ZnO:Al
Zinc oxide and aluminum are used to prevent alloy formation between silicon and metal layers.