Enhancing performance of two-step fabricated perovskite solar cells with sulfonium triflate-based additive

We incorporated triphenylsulfonium triflate (TPST), a sulfonium-based additive consisting of polar triflate and bulky hydrophobic phenyl rings, to the PbI₂ precursor solution for preparation of less-defect perovskite film via two-step fabrication. TPST induced localized alterations in the array of the PbI₂ structure due to its large size, thereby forming a more discontinuous and coarser surface with a greater number of pinholes and subsequently facilitating more efficient organic–inorganic reactions. As a result, we achieved the production of thick perovskite films with enlarged granules and decreased PbI₂ residuals in the two-step fabrication process. Furthermore, TPST facilitated the passivation of bulk film defects by increasing the binding energy with the defects. Consequently, the ITO/SnO₂ np-based device and the FTO/CBD SnO₂-based device obtained the best PCEs of 23.88% and 24.30%, respectively. Furthermore, the moisture stability of the perovskite was improved by the hydrophobic character of the TPST additive.