Rapid thermal evaporation of Bi2S3 layer for thin film photovoltaics

• High quality Bi2S3 film was fabricated by a rapid thermal evaporation process.
• Optical and electrical properties of Bi2S3 film were investigated in detail.
• ITO/NiO/Bi2S3/Au thin film solar cells obtained an efficiency of 0.75%.

Bi2S3 is a promising inorganic material for thin film photovoltaic application with optimum direct band gap of ~1.3 eV, strong absorption coefficient, nontoxic and simple composition. Here we introduce rapid thermal evaporation (RTE), a method with simple facility and extremely fast deposition speed, to produce high quality Bi2S3 films. By optimizing the substrate temperature and post-annealing process, well-crystalline, smooth and compact Bi2S3 films were obtained. The band gap, doping type and density, and photosensitivity of as-produced Bi2S3 films were revealed by a combined X-ray diffraction, Scanning electron microscopy (SEM), Raman spectrum, X-ray photoelectron spectroscopy (XPS), Energy dispersive spectroscopy (EDS), Hall effect and photoresponse measurements. Finally, a prototypical ITO/NiO/Bi2S3/Au solar cell with 0.75% power conversion efficiency was obtained, manifesting the promise of Bi2S3 as the absorber layer for thin film photovoltaics.