Energy Environ. Sci. http://doi.org/bhwc (2016)
Thin-film solar cells such as those with Cu(In,Ga)Se2 absorbers are promising alternatives to Si solar cells, and now reach efficiencies of over 22%. While the best performing Cu(In,Ga)Se2 devices are produced by relatively expensive vacuum deposition, solution processing can lower the production costs, making thin-film technologies more competitive. Efficiencies of over 15% have been achieved in spin-coated samples, but by means of toxic or unstable inks that are unsuitable for industrial production. Xianzhong Lin and colleagues in Germany and Qatar now report the fabrication of Cu(In,Ga)Se2 solar cells using a drop-on-demand inkjet printing method that is efficient in its use of raw materials and compatible with scalable production processes. Inkjet printing can reduce the material wastage by about a factor of ten compared with spin coating.
A Cu–In–Ga nitrate precursor ink that is stable in air and at room temperature is printed on a substrate and annealed to form a 1-μm-thick compact absorber layer. This layer is not uniform in composition, and is made from a top, thicker layer with large grains, and a bottom layer with smaller grains, which is thought to be inactive. Solar cells fabricated with this absorber have an efficiency of 11.3%, which might be further increased by increasing the thickness of the absorber and optimizing the annealing conditions.
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De Ranieri, E. Thin-film solar cells: Joining the print club. Nat Energy 1, 16083 (2016). https://doi.org/10.1038/nenergy.2016.83