CuSbS2 thin films by rapid thermal processing of Sb2S3-Cu stack layers for photovoltaic application

- CuSbS2 thin films by annealing and rapid thermal processing of Sb2S3-Cu.
- The films exhibit direct bandgap 1.5-1.6 eV and p-type conductivity.
- Glass/ITO/CdS/CuSbS2 PV structure performance of Voc=665 mV and FF=0.62.

Copper antimony sulfide (CuSbS2) thin films were prepared by annealing and rapid thermal processing (RTP) of Sb2S3-Cu precursor layers at different conditions. Sb2S3 thin films (200 nm) were deposited by chemical bath deposition from a solution containing SbCl3 and Na₂S₂O₃. Copper layers were thermally evaporated onto the Sb2S3 thin films. A systematic study was done by varying Cu layer thickness as well as the heating conditions. Cu thickness was varied from low (<10 nm) to 100 nm and the heating conditions were annealing at 380 °C, RTP at 500/600 °C and annealing at 380 °C followed by RTP. The thin films formed at different conditions were analyzed using different techniques to determine their crystalline structure, morphology, elemental composition, chemical state and physical properties. For the given Sb2S3 thickness, Cu 50 nm was identified as the effective Cu thickness for the formation of CuSbS2. The CuSbS2 thin films formed at different conditions were incorporated in photovoltaic structures of superstrate configuration: Glass/ITO/CdS/CuSbS2. The best photovoltaic parameters obtained were Voc=665 mV, Jsc=1.35 mA/cm2, FF=0.62 and η=0.6% measured under illumination using AM1.5 radiation from a solar simulator. Voc and FF are the highest values ever reported for the CuSbS2 based solar cells. The present work strengthens the research activities to improve CuSbS2 based photovoltaic performance, and thus PV technologies using earth abundant and non-toxic materials.

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