Over 10% Efficient CuIn(S,Se)2 Thin Film Solar Cells Fabricated from Molecular Precursor Ink

We report the fabrication of solution-processed CuIn(S,Se)2 thin film solar cells based on deposition from molecular ink. These thin films were produced by spin coating of ink containing CuCl, InCl3, and thiourea dissolved in methanol, followed by selenization at high temperatures. X-ray diffraction analysis suggests that the as-coated film was low-crystalline CuInS2 which converted into high-crystalline mixed sulfur-selenium CuIn(S,Se)2 alloy after the selenization process at 550 °C. Solar cells were fabricated from CISSe films by coating with a CdS layer (chemical bath deposition) and ZnO/ITO bilayers (sputtering). The device showed a power conversion efficiency of 8.3% (Jsc : 35.17 mA cm-2, VOC: 0.43 V, FF: 54.81%). After modification of the spin coating process, power conversion efficiency as high as 10.10% (Jsc : 36.51 mA cm-2, VOC: 0.45 V, FF: 61.09%, no anti-reflection coating) was achieved from the device using a relatively thick CISSe film (~3.8 µm).