Photovoltaic research equipment in Delft

ADEM invests in advanced equipment, to build a shared and open Innovation Laboratory specialized in research on materials used in energy conversion, energy storage, and energy transport. A good example of  this can be found within the Photovoltaic Materials and Devices group (PVMD) at Delft University of Technology. Here the Amigo cluster tool; a  radio frequency plasma enhanced chemical vapor deposition (RF PE-CVD) machine, enables a wide range of experimental projects.

The PVMD group works on innovative materials and novel device structures to improve photovoltaic technologies. One of the defining strengths of the PVMD group is its ability to fabricate complete thin-film silicon solar cells on a variety of carriers, both in substrate as in superstrate configuration. The group possesses several tools to deposit silicon-based films, metal electrodes and transparent conductors. Layers and devices can be characterized optically, electrically, and structurally by a variety of specialized measurement tools.

Flexible and with maximum purity
One of the crucial deposition tools is the Amigo cluster tool, partly funded by ADEM. The Amigo is a multi chamber system consisting of a central Transport Chamber (TC) equipped with a robot arm. Six Deposition Process Chambers (DPC’s) and a load lock are connected to the TC. In the DPC’s, amorphous and micro crystalline intrinsic and doped silicon, as well as silicon alloys can be deposited by Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD). Furthermore, Transparent Conductive Oxide (TCO) can be deposited by RF-magnetron sputtering. The system is fully automated, so once programmed, complex devices can be deposited easily.

To achieve state of the art material properties, layers are deposited in Ultra-High Vacuum (UHV, 10-9 mbar) chambers. The Amigo load lock can be pumped down from atmospheric pressure to high vacuum (10-6 mbar) within a few minutes. Once introduced in the cluster tool, substrates can be processed layer by layer without breaking the vacuum. Low leak- and outgassing rates of the chambers, together with the use of high purity process gases, are the prerequisites to deposit high quality material. Cross contamination between the different processes is prevented by using dedicated processing chambers for each type of material.

Within the PVMD group, the Amigo is used in a wide range of research topics, including the research of amorphous silicon (a-Si:H) and nanocrystalline silicon materials and solar cells and the design and optimization of back reflectors and intermediate reflectors. It is also used in studies into the metastability of a-Si:H (Staebler-Wronski effect) and light trapping studies with textured substrates.

Research freedom in ADEM project
Martijn van Sebille, one of the ADEM PhD's working with Amigo : “Because of the six separate chambers, I can experiment in one chamber without disturbing critical parameters for other researchers using the other chambers.” Which is an important feature, for Amigo is maximum occupied equipment. 

 'Amigo has to be booked weeks in advance'

Martijn explains, “ I guess that more than half of the researchers in our group use the AMIGO regularly and also some external researchers. Even during weekends it's highly occupied “, emphasizes Martijn.

Martijn works on silicon quantum dots embedded in a high band gap amorphous silicon alloy. The goal is to create a low-cost and non-toxic material with the ability to fine-tune the material’s band gap. Such a material could be used to create economically  competitive multi-junction solar cells. This could greatly enhance the performance of affordable solar cells. Also for this research, the Amigo cluster tool is an essential tool. The very first step in making the embedded silicon quantum dots is the deposition of the host material, after which a post-treatment with an excimer laser is performed to crystallize silicon into quantum dots. By tuning the process conditions like gas flow rates and ratios, process pressure, temperature, RF power and electrode distance, the Amigo cluster tool provides Martijn practically unlimited freedom in tuning the properties of the initial layer, which will greatly influence the outcome of any post-treatment.

For more information about the PMVD group Delft led by professor Miro Zeman or the research equipment, please call 015 27 86259 or mail to for more information about Martijn van Sebille and his project.