Thin-film CZTSe solar cell from Solliance and imec reaches 9.7% efficiency
Unlike CIGS (Cu(In,Ga)(S,Se)2) and CZTS (Cu2ZnSnS4) devices, CZTSe does not suffer from material resources issues. At 1.5-1.6eV for CZTS, and 0.9eV for CZTSe, their bandgaps make a combined material system suitable for a multi-junction, thin-film solar cell that rivals the efficiency of CIGS cells (about 20 percent).
Imomec, imec and Solliance have defined a path towards further improving the layers and cell structures of CZTSe and CZTS absorbers aiming at developing a multi junction CZTS/CZTSe solar cell with 20 percent cell efficiency. The 1x1cm prototype CZTSe solar cell is a first step.
Imec/imomec fabricated the CZTSe layers by sputtering Cu, Zn and Sn metal layers on a Molybdenum-on-glass substrate and subsequent annealing in an H2Se containing atmosphere, achieving 9.7 percent efficiency.
The resulting polycrystalline absorber layers are only 1µm thick, with a typical grain size of about 1µm. The samples were then processed at Helmholtz Zentrum Berlin into solar cells using a standard process flow for thin film solar cells and finished with a metal grid and anti-reflective coating at imec. The highest efficiency obtained on a 1x1cm cell was 9.7 percent, with a maximum short circuit current of 38.9mA/cm2, an open circuit voltage of 0.41V and a fill factor of 61 percent.
“This is a big win for us. We’ve been working toward this milestone since 2011 when we first started our research on alternative materials for thin-film photovoltaics at imec/imomec,” said Marc Meuris, program manager Solliance of the alternative thin-film PV program. “Our efficiencies are the highest in Europe and approaching the world record for this type of thin-film solar cells, and we look forward to further advancing R&D to help bringing to market sustainable energy sources.”
Visit imec at www.imec.be
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