TU Delft student sets new tandem thin film silicon efficiency record

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Hairen Tan has achieved a conversion efficiency record for a tandem thin film silicon cell, using amorphous silicon and nanocrystalline silicon absorber layers. Tan was able to stack the PV materials in such a way that an improved utilization of the light spectrum was achieved.

Light trapping technology also played a role in the record. Tan developed a “modulated surface texture” approach, which scattered and absorbed the light more efficiently. The approach required Tan to design a “novel surface morphology” of a glass substrate through etching. “Nano-scale features of a transparent electrode [were] deposited on the etched glass,” a statement announcing the world record reads.

The third achievement within the result relates the quality of the semiconductor material Tan was able to achieve. TU Delft reports that both the amorphous and nanocrystalline silicon layers were of “exceptional electronic quality.” Tan collaborated with the EPFL laboratory in Neuchatel, Switzerland, to employ the research body’s transparent electrodes – which minimize optical losses beyond the absorber layers.

Tan expects to achieve a conversion efficiency of 15% with his technique. The PhD candidate was supervised by TU Delft’s Arno Smets and Miro Zeman in his endeavours.

The record setting findings were presented at the 6th World Conference on Photovoltaic Energy Conversion, held last month in Kyoto. TU Delft also presented a quadruple junction cell at the conference, with which an efficiency of 11.4% was achieved.