TECHNOLOGY MATTERS
In the solar based photo voltaic industry, we distinguish between two basic module technologies - crystalline and thin film.
Crystalline technology
Crystalline solar modules (mono or polycrystalline) are made by cutting wafer-thin slices of silicon crystal, known as wafers, and fitting them with contacts.
The manufacturing technology is relatively expensive. However, the efficiency is currently higher than that of thin film modules of equivalent area. The currently most popular technology is based on the use of crystalline silicon. Here, high purity silicon ingots are cut into very thin slices called wafers.
To produce a solar cell, the characteristics of these slices are altered by intentionally introducing a impurity (doping). Anti-reflection layers are applied to the front of the cell to improve light absorption.
As the usable voltage produced by a single wafer is too low for practical purposes, several slices are connected together in series.
To protect them from physical and environmental harm, the wafer arrangement is sandwiched between a transparent front film and a rear backing film to produce a module.
This technology, which has been perfected for some decades now, dominates the photovoltaic industry with a market share of approximately 80 percent (as at 2008).
Thin film technology
Thin film modules are made by depositing or vapor coating high purity semiconducting materials such as a-Si, CdTe, CIS, CIGS onto a substrate and then applying contacts.
It takes much less energy and fewer raw materials to manufacture thin film modules, which makes them more environmentally friendly and cheaper to produce than crystalline modules. Other benefits of thin film technology are greater energy yields both at high temperatures and under diffuse light conditions. By exploiting potential efficiencies in the production process, continuing to improve the efficiency of existing technologies, and exploring new technological approaches, thin film technology is becoming increasingly competitive.
The newer thin film technology does not use technical silicon wafers; the functional layers are applied to a substrate - usually glass - via vacuum deposition. The processes involved are similar to those used in coating architectural glass or in the manufacture of flat screen televisions. The same basic design - front contact, absorber, and rear contact - is the same as the one used in crystalline technology, but the material and energy requirements of the manufacturing process are much lower.
While the crystalline technology uses wafers of approximately 250µm, thin film technology absorbers are no more than a few micrometers thick.
Thin film technology is gaining ground. Its market share is growing rapidly and currently stands at around 20 percent (2008; 2005: 5.8 percent, 2007: 14 percent).
Efficiency – cost is related to output
We at DSI believe that Crystaline technology by far is the most cost effective technology. It has been around for many years and is well proven.
Our solar panels/modules are testes to work for up to 40 years. As to the Thin film technology we find that efficiency is still much lower than Crystaline and the life span is more than 50 % shorter. We however acknowledge that Thin film can be used with great success in specific applications where a solar panel would be difficult to use. That is military applications and other portable applications. BUT for the intent to produce power in a Solar Park solution we strongly advice to use Crystaline technology as both output and life time is far greater that other technologies.
