Weiss T.P., Minguez-Bacho I., Zuccalà E., Melchiorre M., Valle N., El Adib B., Yokosawa T., Spiecker E., Bachmann J., Dale P.J., Siebentritt S.
Progress in Photovoltaics Research and Applications, vol. 31, n° 3, pp. 203-219, 2023
Currently, Sb<sub>2</sub>Se<sub>3</sub> thin films receive considerable research interest as a solar cell absorber material. When completed into a device stack, the major bottleneck for further device improvement is the open-circuit voltage, which is the focus of the work presented here. Polycrystalline thin-film Sb<sub>2</sub>Se<sub>3</sub> absorbers and solar cells are prepared in substrate configuration and the dominant recombination path is studied using photoluminescence spectroscopy and temperature-dependent current–voltage characteristics. It is found that a post-deposition annealing after the CdS buffer layer deposition can effectively remove interface recombination since the activation energy of the dominant recombination path becomes equal to the bandgap of the Sb<sub>2</sub>Se<sub>3</sub> absorber. The increased activation energy is accompanied by an increased photoluminescence yield, that is, reduced non-radiative recombination. Finished Sb<sub>2</sub>Se<sub>3</sub> solar cell devices reach open-circuit voltages as high as 485 mV. Contrarily, the short-circuit current density of these devices is limiting the efficiency after the post-deposition annealing. It is shown that atomic layer-deposited intermediate buffer layers such as TiO<sub>2</sub> or Sb<sub>2</sub>S<sub>3</sub> can pave the way for overcoming this limitation.
