Fully printable Sb₂S₃-based mesoscopic triple-stack solar cells: the influence of infiltration chemistry

The rise of screen printable mesoscopic triple-stack solar cells infiltrated with lead halide perovskites is a milestone in the pursuit of scalable perovskite solar cells. This architecture has been developed to benefit from the excellent transport of charge carriers in the perovskite itself. Consequently, it is possible to incorporate a mesoporous insulating zirconia scaffold into the device architecture and prevent shortcuts between mesoporous titania and carbon films. The use of other absorbers besides lead halide perovskites has not yet been thoroughly explored, probably due to the less competitive charge carrier transport properties of other photoactive materials. In this work, Sb₂S₃ precursors were infiltrated through the mesoscopic stack, and the photovoltaic properties of the solar cells were analysed. A one-step protocol allowed the preparation of an Sb₂S₃ absorber; however, the solar cells showed poor photovoltaic response. The modification of this procedure by adding a previous infiltration step (two-step protocol) of a PbI₂ solution in DMSO significantly improved the infiltration of the Sb₂S₃ photoactive layer through the mesoscopic stack, which resulted in an increase in its photovoltaic activity. Only small amounts of PbI₂ were needed, which resulted in the formation of a small proportion of Pb₂SbS₂I₃. Although this phase was not photoactive, the PbI₂ inclusion significantly improved the solar cell performance with negligible hysteresis in the current-voltage curves. Reproducible efficiencies were obtained using volumes of 0.4 M PbI₂ solution ranging between 10 and 5 μL with a highest mean power conversion efficiency of 0.57% for 5 μL. The efficiency values were more dispersed for cells prepared with 2.5 μL of PbI₂ solution with a mean value of 0.65%, but a champion cell with an efficiency of 0.8% was obtained. However, the condition using 5 μL of PbI₂ solution exhibited superior reproducibility and stability, highlighting a trade-off between peak performance and device consistency across the batches. An optimized, minimal thickness of a mesoporous zirconia film increased the photovoltaic activity of devices, thus suggesting a potential route to facilitate infiltration of mesoscopic stacks with non-perovskite fully inorganic materials as absorbers.