Work

Direct Microscale Observation of Additive-Triggered Reduction in Tin Halide Perovskites

Year: 2026

Type: article

Abstract: We investigate the nanoscale function of additives used for tin-containing perovskites, using the archetypal FASnI3 (FA = formamidinium). First, we find that the addition of sodium borohydride (NaBH4) is inhomogeneous, with 200–500 nm aggregates forming on the FASnI3 surface. The inhomogeneous distribution of NaBH4 leads to a relatively small (∼1% of the film) amount of reduced perovskite, but the macroscopic properties are dominated by the overwhelming space without any treatment. Upon illumination, more aggregate regions (∼13%) become activated due to reduction of photogenerated I2. On the other hand, when we combine NaBH4 with dipropylammonium iodide (DipI) passivation and illuminate, we observe a much more homogeneous activation effect, which we attribute to denser coverage of NaBH4. We find that the iodine content in FASnI3 films treated with NaBH4 and DipI is 64% less than in those treated with NaBH4 alone. These results underline that the microscale configuration of different additives in tin perovskites is deeply interconnected and it is essential to uncover their chemical reactivity.

Source: ACS Energy Letters

DOI: 10.1021/acsenergylett.6c01751