Detailed photoluminescence study of vapor deposited Bi2S3 films of different surface morphology (Phys. Status Solidi B 11/2014)

Sträter et al. (pp. 2247–2256) present a detailed photoluminescence (PL) study on the binary semiconductor bismuth sulfide (Bi2S3). Due to its band gap of about 1.3 eV and its non‐toxicity it is regarded as a potential thin film solar cell absorber. The films prepared by physical vapor deposition show a varying surface morphology in terms of roughness and surface structure. By temperature and excitation‐intensity PL experiments Sträter et al. located different defect levels within the band gap. The authors also determined a splitting of quasi‐ Fermi levels (QFL), which can be interpreted as the upper limit of the open circuit voltage, of about 700 meV and an optical band gap of about 1.3 eV at room temperature. By laterally resolved PL measurements they show that a full analysis of the laterally resolved maps is necessary to interpret the lateral variation properly. This includes a detailed analysis of each PL spectrum and the energetic position of its maximum as well as a determination of the QFL splitting, optical band gap, Urbach energy, defect PL yield, and defect absorption to identify properties with opposing effects.