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The crystalline Silicon : the most wide spread and used technology

Crystalline Technology | Thin Film Technology

Two main families of silicon photovoltaic panels are available on the market : thin film and crystalline technologies. These are the main industrial routes used nowadays.

Crystalline Technology

This technology is using one of the most present element within the earth's crust: Silicon. Silicon is widely spread notably under silica or sand and arrives just after oxygen regarding its availability within the soils.
The silicon is used under two different shapes in the photovoltaic industry: mono and multi- crystals. Depending on its silicon origin, the corresponding PV cells are accordingly called multi or mono crystalline.

The crystalline technology operates with very thin plates (150 to 200 µm, that is to say 0,15 à 0,2 mm), cut within an ingot of silicon produced through melting and molding. The Cells are finally connected electrically together in series, for to be set and sticked on the back face in glass which by itself is a protection against atmospheric and mechanical aggressions. The yield of these cells is the range of 14 to 17 %. A new record had been achieved end August 2009 at an industrial scale on the multi-crystalline panels: 15.7 %.

This kind of technology counts for about 90 % of the market in 2007 (43 % for mono and 47% on poly). It is the most used way to install solar cells and the improvement potential is still significant [source :PWC State of the art in the PV industry - France March 2009]

Thin Film Technology

The thin film cells are produced by deposition of one or multiple semiconducting layers on a media of glass, plastic, steel … this technology allows to decrease significantly the production costs, but presents photovoltaic yields ( from 5 to 13 % ) which are reduced compared to mono or multi crystalline cells. The most frequent thin film panels are produced with amorphous silicon or CIGS ( Cupper Indium Gallium di-selenide ) , sometimes with silicon deposition on a flexible material.

Two options with amorphous silicon appeared for a few years : the routes using Telluride Cadmium ( CD Te ) and CuInSe2 ( Cupper Indium Di-Selenide) with a variant called CIGS ( Cu(In,Ga)Se2 ). These technologies deal with cells having yields from 8 to 11 %, much less efficient than those using silicon crystalline.

The thin film technology is currently developing rapidly, its market share raised within the last 3 years from 2 to 10 %. The reason of this booming is mainly caused by lower production costs. However, raw materials availability and environmental concerns ( Cadmium, Selenium and heavy metals toxicity in general ...) will undoubtedly limit the expansion potential of these routes on a mid-term basis.

Raw materials becoming rare before 2040

The resources for some of the raw materials used in the cells production ( as known in 2002 ) are very weak when compared to the requirement of the photovoltaic industry. The ratio resources/consumption is about 20 to 30 years only with the current best estimates. The risks of shortage of these materials ( Silver, Indium, Ruthenium ) for the photovoltaic industry is huge, especially when considering that these raw materials are already used for other purposes.

To produce 26% of the electricity consumption through the photovoltaic energy in 2040, a cumulated power of 7 TWp (Tera Watt Peak) will have to be built.

This installed power require the corresponding supply of the raw materials involved in the PV industry. Some of these resources ( with the current known data ) are limited and enable the supply of potential quantities well below the needs of the photovoltaic industry like Silver ( 2.6 TWc, CIGS route ) and the Ruthenium ( 0.3 TWc, TiO2 route ), telluride ( 0.74 TWc, CdTe route ), Indium ( 0.2 TWc, CIGS route). Some improvement will have to be performed on the previous technologies to decrease or replace the usage of these raw materials.
(Source : INES education)

The silicon route is the single one capable to fullfil the requirement of the soilar industry and its huge fast development on a mid and long term basis, knowing that silicon is present everywhere within the soils from quartz to silica ( second element by order of presence within the soils, after oxygen ).

M3PSOLAR is recognized for its expertise on the whole value chain: from the Silicon up to the photovoltaic final installation and their connection to the grid.

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