Efficient CuInS2 thin-film solar cells prepared by a sequential process

CuInS2-based thin-film solar cells are presented with 11.1% total area effi ciency or 12.5% active area efficiency. This is the best efficiency reporte d so far for this type of solar cell. The technology is based on a sequenti al process using d.c. magnetron sputtering of the metals and sulphurization in elemental sulphur vapour without the use of a toxic gas. Absorber layer s and solar cells with precursor atomic copper to indium ratios between 1.0 and 1.8 are analysed. The best cells with fewest defects are made from the most copper-rich CuIn precursor layers. The solar cell performance, howeve r, decreases only slowly for small deviations of the Cu/In ratio from the o ptimum value.