Additive-Assisted Optimization in Morphology and Optoelectronic Properties of Inorganic Mixed Sn-Pb Halide Perovskites

Halide perovskite solar cells (HPSCs) are promising photovoltaic materials due to their excellent optoelectronic properties, low cost, and high efficiency. Here, we demonstrate atmospheric solution processing and stability of cesium tin-lead triiodide (CsSnPbI3) thin films for solar cell applications. The effect of additives, such as pyrazine and guanidinium thiocyanate (GuaSCN), on bandgap, film morphology, structure, and stability is investigated. Our results indicate the formation of a wide bandgap (>2 eV) structure with a mixed phase of tin oxide (SnO2) and Cs(Sn, Pb)I-3. The addition of pyrazine decreases the intensity of SnO2 peaks, but the bandgap does not change much. With the addition of GuaSCN, the bandgap of the films reduces to 1.5 eV, and a dendritic structure of Cs(Sn, Pb)I-3 is observed. GuaSCN addition also reduces the oxygen content in the films. To enable uniform film crystallization, cesium chloride (CsCl) and dimethyl sulfoxide (DMSO) additives are used in the precursor. Both CsCl and DMSO suppress dendrite formation with the latter resulting in uniform polycrystalline films with a bandgap of 1.5 eV. Heat and light soaking (HLS) stability tests at 65 degrees C and 1 sun for 100 h show all film types are stable with temperature but result in phase segregation with light exposure.

Automated summary

In this study, the atmospheric solution processing and stability of cesium tin-lead triiodide (CsSnPbI3) thin films for solar cell applications were investigated. The effect of additives, including pyrazine and guanidinium thiocyanate (GuaSCN), on the properties and stability of the films was studied. Results showed that the addition of pyrazine reduced the intensity of tin oxide peaks, while the addition of GuaSCN decreased the bandgap and oxygen content of the films. Furthermore, the use of cesium chloride (CsCl) and dimethyl sulfoxide (DMSO) additives enabled uniform film crystallization.