Consumable CdS nanolayer enables increased performance in kesterite solar cells

Although the ohmic-contact and electrostatic field can be regulated by the intermediate layer for efficient carrier extraction, challenges remain in high-quality back contact as well as improved quality of crystallized CZTSSe absorber layer simultaneously. Here, we introduce a controllable CdS nanolayer prepared by the chemical bath deposition (CBD) process between the CZTS precursors and Mo back contact. The results disclose that the surface chemistry of the naked Mo film can be modified by the formed CdS nanolayer and thus MoS2 complex during the chemical bath process. However, such CdS nanolayer and MoS2 complex can be readily consumed during the following selenization process, without deteriorating the ohmic-back contact. Simultaneously, the as-grown CZTSSe absorber is not only with high crystallinity and less composition fluctuations, but also doped by Cd2+. Subsequently the efficiency of CZTSSe solar cells is increased by 26% as CdS nanolayer is introduced. This work provides a cost-effective and universal approach to design and modify the interface or surface of photovoltaic and photoelectrochemical devices. [Display omitted] •Controllable CdS intermediate nanolayer through the chemical bath deposition is introduced between the kesterite precursors and Mo back contact.•Surface chemistry of Mo film can be modified by the chemical bath solution, with CdS and MoS2 complex formation.•Introduced CdS intermediate nanolayer is readily consumed after selenization process, without deteriorating the ohmic-back contact, accompanied by enhancing the crystallinity of CZTSSe film.•Defect characteristics in CZTSSe solar cells are optimized by Cd2+ doping, thus improving device performance.