Department of Engineering Sciences

Diploma thesis project


A 30 hp diploma thesis project on "High temperature transparent conductors for tandem solar cells" is currently available.


Tandem solar cells can provide conversion efficiency higher than 33%, the limit for a single junction solar cell. Instead of using a single junction, two solar cells stacked on top of each other can reach 46% efficiency.  CIGS (CuInxGa1-xSe2) is a promising material for tandem solar cells due to its high efficiency and tuneable band-gap. While the bottom cell uses established material stack, the top cell requires a transparent back contact which replaces the traditional Mo layer. In the case of CIGS, the transparent contact has to withstand high temperature required for processing of the top cell.

Among the established transparent conducting oxides (TCO), tin oxide SnO2 offers exceptional chemical stability, high hardness, and excellent thermal stability. Although fluorine doped SnO2 is stable up to 900 °C in air, it fails in contact with CIGS. The purpose of this thesis is to develop an alternative TCO material and test it with solar cells.

Recombination layer is a critical part of tandem solar cells (left), it has to be transparent and provide efficient recombination of charge carriers. In this project, the goal is to develop a transparent CIGS solar cell where the traditional Mo back contact is replaced by transparent SnO2 conductor (right).


The main goal is to identify suitable doping element and establish a deposition process for the transparent contact layer. The work also includes optical and electrical characterization of the material. If time permits, complete solar cells will be fabricated and characterized.

Your profile

Minimum 4 year of engineering (civilingenjör) studies in physics/materials engineering or chemistry or equivalent. Interest in laboratory work and materials science.


Tomas Kubart:
Tobias Törndahl:

Starting date

As soon as possible

More information


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