Glossary

Amorphous solar cells

Amorphous Si-solar cells are manufactured through sputtering or vacuum deposition. The efficiency is less than for crystalline solar cells.

Vacuum deposition

Vacuum deposition or thermal deposition is a PVD process coating technology under vacuum. This is a process in which the entire basic raw material is heated by electric heating (resistive or inductive) to temperatures close to the boiling point, the material vapor is channeled towards a substrate and condenses to a layer.

Buffer layer

Isolation and barrier layers as buffer layers are of vital importance in the thin-film technology. They are used for electric separation of charge or diffusion barrier, for example.

CdTe (Cadmium telluride)

Semiconductor used instead of silicon for the production of thin-film cells. It is used as a layer structure with cadmium-sulfide to form a pn-junction, e.g. for a solar cell.

CIGS cells

Thin-film cells for which the coating material copper-indium-gallium-(di)selenide (CIGS) is applied to a substrate (e.g. glass or stainless steel foil).

Degradation

Degradation or deterioration indicates the reduction in efficiency of a solar cell in the course of its lifetime.

Efficiency

Specifies the efficiency (ratio of emitted to generated energy) of individual energy-generating components or entire systems. Material system laboratory efficiency levels

Silicon (amorphous) 5-10 %

Silicon (poly-crystalline) 17-19 %

Silicon (mono-crystalline) 19-21 %

PERC 21.3 %

PERT 22.2 %

Heterojunction 25.6 %

CIGS 22.3 %

Cadmium telluride 5-12 %

Perowskit (prototypes) 20.1 %

Heterojunction solar cells

For heterojunction solar cells, for the manufacturing of the electric structures on an n-conductive silicon wafer, on both sides thin layers of doped and intrinsic, amorphous silicon as well as transparent oxide layers (TCO) are applied for the absorption of the generated power. Due to the high level of light yield and the excellent passivation characteristics of the amorphous silicon, it is possible to achieve efficiency levels for the modules of more than 22 %.

Ingot

Describes a block made of semiconductor material, e.g. silicon. Can be built on mono-crystalline or poly-crystalline structures. For the manufacturing of solar cells, ingots are cut into wafers.

Crystalline solar cells

Consist of high-purity, crystalline silicon. Depending on crystal structure one distinguishes between mono-crystalline solar cells and poly-crystalline solar cells. Generally, crystalline solar modules have a higher level of efficiency than thin-film solar modules and achieve more gain on smaller surfaces.

kWp

The size of a photovoltaic system is specified by its output in kWpeak (kWp) (peak output). This value describes the optimum output of solar modules under standardized test conditions (1000 W/m² irradiation, 25 °C module temperature, 1.5 air mass).

Mono-crystalline solar cells

Mono-crystalline solar cells are manufactured from round mono-crystals (ingots) with 30 cm diameter and several meters length e.g. according to the Czochralski process. The results are mono-crystals, from which wafers are produced.

MW/a

Production capacity of a solar cell production facility or output of a single production plant specified by the peak output in megawatts per year.

Wet-chemical processes

Process steps for the solar cells manufacturing such as e.g. cleaning, texturing, etching and coating through chemical bath deposition of solar wafers and solar cells.

Organic solar cells

An organic solar cell is a solar cell consisting of elements of organic chemistry, i.e. of hydrocarbon compounds (plastics).

Peak output

Peak output of a solar module. Specified through a small “p” after the energy output watt: Wp. The peak output specifies the output achieved by a solar module under full irradiation. Often also called "nominal value" or "nominal output" and based on measurement under optimum conditions.

PECVD

Plasma-enhanced, chemical vapor deposition. A coating process for the application of thin passivation and antireflection layers mostly applied under vacuum.

PERC / PERT solar cells

PERC cells are produced on so-called p-type wafers. The coating with aluminum oxide is one of several methods to produce so-called PERC high-efficiency cells. Most manufacturers use PERC on mono-crystalline wafers, however, some produce these high-efficiency cells also on poly-crystalline wafers. PERT is a similar concept for the manufacturing of high-efficiency cells such as PERC, only difference being that the PERT cells are manufactured with n-type wafers. In principle, high levels of efficiency can be achieved with n-type wafers than with p-type wafers.

Photovoltaics

PV-technology, which enables the transformation of solar energy into electric energy.

Poly-crystalline solar cells

Poly-crystalline solar cells are produced from silicon blocks (40 cm x 40 cm x 30 cm) in a so-called ingot casting process. The ingots are then processed to wafers.

Reflection

The solar irradiation reflected from a surface. The reflection of the Earth’s surface amounts to about 20 %.

Selenization

Selenization or sulfurization is the application of a function layer in an oven amid temperatures of 550 °C. The selenium or sulfur sources are hydrogen selenide H2SE or hydrogen sulfide H2S.

Silicon

Chemical element, a metalloid and therefore a semiconductor. In its high-purity form used in our solar cells, usually in thin disks, so-called silicon wafer.

Solar modules

Consisting of solar cells transforming solar irradiation into electric energy.

Solar electricity

Colloquial for electric energy transformed from solar irradiation. Part of renewable energies and promoted in Germany by the Renewable Energies Act

Solar cells

Transform solar irradiation into electric energy. Positive and negative charges are generated through solar irradiation. Environmentally-friendly power is generated. More than 80 % of the solar modules are made of silicon.

Sputtering

Cathode sputtering, also sputtering, is a physical process, during which atoms are transmitted from a solid body target by high-energy ion bombardment, transition towards a gas stage and are then channeled in a controlled way towards a substrate where they condense in a layer.

System efficiency photovoltaics

The overall or system efficiency level of a photovoltaics plant is the result of several factors. If the generated direct current is transformed into alternating current, transformation losses are incurred at the converter. If the power is stored in a storage battery for off-grid systems, energy is also lost during the storage process. The length of the power lines also impact losses.

Thin-film solar cells

The difference to crystalline solar cells is that the semiconductor material is directly applied to so-called substrates (e.g. glass, plastic, foil or metal) in one or several very thin layers. This enables many new application areas for photovoltaics (e.g. roof elements made of metal, face elements made of glass). As semiconductor material so-called amorphous silicon (a-Si) is used or cadmium telluride (CdTe) as well as copper-indium-diselenide (CIS) or copper-indium-gallium-diselenide (CIGS).

Vacuum coating

Vacuum coating vapor deposition in physics terms. Through physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes, the raw material is transformed into the vapor phase. The gaseous material is subsequently channeled towards the substrate to be coated, where it condenses and forms the target layer.

Wafer

Wafer-thin, mostly square disks made of silicon, from which solar cells are manufactured.

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