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

Abstract We incorporated triphenylsulfonium triflate (TPST), a sulfonium‐based additive consisting of polar triflate and bulky hydrophobic phenyl rings, to the PbI 2 precursor solution for preparation of less‐defect perovskite film via two‐step fabrication. TPST induced localized alterations in the array of the PbI 2 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 PbI 2 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/SnO 2 np‐based device and the FTO/CBD SnO 2 ‐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. image