Silicon photovoltaics

Photovoltaics manufacturer SCHOTT Solar has entered into a three-year research partnership with IMEC.

SCHOTT Solar joins IMEC’s newly launched silicon photovoltaics industrial affiliation programme (IIAP). Within this research-and-development programme, IMEC aims to explore and develop advanced process technologies to fuel the steep market growth of silicon solar cells in a sustainable manner. The programme will concentrate on a sharp reduction in silicon use, while increasing cell efficiency in a bid to substantially lower the cost-per-Watt peak.

‘We are excited that one of the leading photovoltaics manufacturers joins our multi-partner programme. Building on our 25-year track record in silicon solar cells and our successful experience with industrial affiliation programmes on CMOS scaling, we are confident that we will provide our partners a dynamic research platform for accelerated process development,’ said Jef Poortmans, programme director of Solar+ at IMEC.

Crystalline silicon solar cells account for more than 90 per cent of the world’s solar cells. Within its IIAP, IMEC aims to reduce the cost of producing crystalline silicon solar cells and the amount of Si/Watt that is needed by half. Efficiencies of about 20 per cent are targeted.

IMEC’s programme will explore wafer-based bulk silicon solar cells and epitaxial cells. Within the bulk-silicon solar-cell sub-programme, generic process technology, crucial for increased efficiency and manufacturing cost reduction, will be developed.

The active silicon layer thickness will be reduced from 150µm down to 40µm. To meet efficiencies of about 20 per cent, alternative back-side dielectric stacks and interdigitated back-side contacts (i-BCs) will be introduced in thin wafers using a passivated emitter and rear local back surface field (PERL)-style concept in an industrial process flow.

Cell module integration will be investigated, since a reduced wafer thickness will impose specific integration requirements. As the guaranteed lifetime of cells and modules will further increase in the next decade from 20-25 years up to 35 years and more, reliability will also be assessed.

Similarly, methods to realise and handle wafers as thin as 40µm will be pursued. The potential of the technology will be benchmarked in small-area laboratory cells and large-area solar cells.

Besides the generic bulk silicon research, which is of relevance for any crystalline silicon wafer-based solar-cell technology, epitaxial thin-film (less than 20µm) silicon solar cells on a low-cost silicon carrier will also be developed.