High Efficiency CIGS Solar Modules

Record efficiency of up to 15.5% on 30 × 30 cm2 and 13.9% on 1 m2 sized fully integrated thin film solar modules have been achieved at AVANCIS using rapid thermal annealing of stacked elemental layers of Cu(Ga), In and Se. The relatively small performance offset between tightly tuned prototype modules from the pilot line and average modules from mass manufacturing demonstrate that scale up of CIGS technology was successful. The key prerequisites in terms of basic semiconductor material properties and coating uniformities leading to high device performance will be described. Namely large area mapping of semiconductor properties via XRF, photoluminescence decay time, Raman spectroscopy and IR thermography have proven instrumental to transfer champion efficiencies from the lab into continuous mass manufacturing. Nevertheless there are further options for improvements of basic device performance. In particular bandgap gradings using indium / gallium grading towards the back of the device and sulphur / selenium grading towards the front of the device show promise for higher open circuit voltages. A second area for improvements concerns the film properties of the front electrode, which is sputter deposited Al-doped ZnO in our case. Via changes in the plasma deposition conditions the trade-off between transmission and conductivity could be optimised and as a consequence the fill factor and short circuit current of the devices improved.