Development of a 21% back-contact monocrystalline silicon solar cell for large-scale production

As a part of its cost reduction strategy, Q-Cells AG is exploring opportunities to fabricate mono-Si solar cells with more than 20% efficiency in mass production. In a joint R&D project, we are developing a back junction cell whose design is compatible with a wider range of silicon material qualities. Two-dimensional device simulations confirm an efficiency potential above 20% if wafers with lifetime > 600 ?s and resistivity of 1-10 ohm cm are used. To obtain this specification, a tight rear pattern is required. Laser processing is identified as a promising patterning technique and can be well integrated in an industrial processing sequence. When fabricating laboratory cells according to this processing sequence, we have obtained efficiencies up to 21% on p- and n-type FZ wafers. On n-type Cz silicon a confirmed efficiency of 21% has been achieved, underlining the feasibility of our back junction solar cell approach. Based on these results, Q-Cells AG has decided to build up a pilot line in Thalheim, Germany.