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Fig. 52: a) Schematic of antisolvent application by pipetting. b) SEM image of triple cation perovskite film formed by pipetting the antisolvent. Red circles mark PbI2 crystallites formed at the surface of the film. c) GIWAXS measurements at the surface and bulk of triple cation perovskite films formed by pipetting the antisolvent. d) Schematic of antisolvent application by spraying. e) SEM image of triple cation perovskite film formed by spraying the antisolvent. No PbI2 crystallites are formed at the surface of the film. f) GIWAXS measurements at the surface and bulk of triple cation perovskite films formed by spraying the antisolvent.

Fig. 53: a) Schematic structure of the photovoltaic devices. b) Power conversion efficiency (PCE) of triple cation perovskite solar cells manufactured by either spraying (blue) or pipetting (red) for different volumes of antisolvent.

ID10 using a 2D Pilatus 300 K detector. To characterise the structure at the surface and bulk of things, the incidence angles were varied from 0° to 0.3° to adjust the probing depth from a few nanometres to hundreds of nanometres. Analysis of the GIWAXS measurements (Figure 52c) revealed that perovskite films made with pipetted antisolvent consisted of approximately 5% PbI2 at the surface, and approximately 3.5% PbI2 in the bulk.

In this work, an alternative method for perovskite film manufacture was investigated, where the antisolvent is applied via spraying, rather than by pipetting (Figure 52d). SEM imaging showed that the surface of the perovskite films exhibits much fewer PbI2 crystallites (Figure 52e), which was confirmed by GIWAXS measurements that showed that the fraction

of PbI2 was reduced to 3% and 2% at the surface and bulk, respectively. These results demonstrate that the use of spraying significantly better preserves the intended stoichiometry of the perovskite layers.

To explore the photovoltaic performance of the pipetted and sprayed perovskite films, they were integrated into inverted architecture device structures (Figure 53a). The devices in which the perovskite layer was processed by spraying the antisolvent consistently showed a higher power conversion efficiency, reaching a maximum of 21%. Importantly, a similarly high-power conversion efficiency of sprayed devices was achieved when the volume of antisolvent was significantly reduced from 200 µL to 60 µL. This highlights that spraying the antisolvent not only leads to a better photovoltaic performance but also enables the reduction of the