Molecularly Tailored SnO₂/Perovskite Interface Enabling Efficient and Stable FAPbI₃ Solar Cells

Abstract

Pure FAPbI3 (where FA is formamidinium) based perovskite solar cells (PSCs) have drawn tremendous attention because of their exceptional photovoltaic properties, although long-term stability is still a big challenge. Molecular tailoring is one of the practical approaches to enhancing the stability of FAPbI3 by passivating the film defects; however, deep understanding of how the molecular configuration affects the adjacent layer in FAPbI3 PSCs is urgently needed. Herein, we report a strategy of molecularly tailoring the FAPbI3/SnO2 interface by employing three Li salts by varying the anion configurations (CO3 2–, C2O4 2–, and HCOO–). When C–O and C=O groups are in optimal configuration, they will form the strongest bonds with uncoordinated Sn4+ and FA+, respectively, which can increase the formation energy of VFA defects, release the residual stress of the FAPbI3 lattice, facilitate the charge transport at the FAPbI3/SnO2 interface, and improve the stability of the PSC. Consequently, we obtained a champion device with a power conversion efficiency of 23.5%, and the unencapsulated device can maintain good stability under continuous light illumination.

Construction of Efficient and Stable FAPbI3 Perovskite Solar Cells through Bifunctional Ionic Liquid‐Assisted Crystallization and Defect Passivation

“…[ 23 ] However, FAPbI 3 ‐based films are plagued by phase transition from the photoactive black phase (α‐FAPbI 3 ) to a nonphotovoltaic yellow phase (δ‐FAPbI 3 ) in ambient conditions at the initial research stage, especially in humid environments. [ 9,24–27 ] In addition, the FAPbI 3 crystal defects formed during solution process not only result in nonradiative charge recombination but also accelerate phase instability, which seriously restricts the PCE and stability of FAPbI 3 ‐based PSC. [ 28 ] Thus, it makes great sense to explore strategies to fabricate high‐quality and phase‐stable FAPbI 3 films to further promote PSCs for commercial utilization.…”

Effective Passivation with Size‐Matched Alkyldiammonium Iodide for High‐Performance Inverted Perovskite Solar Cells

“…For our case, the defect formation energy of V FA was increased after treatment with BDAI 2 (Figure S18, Supporting Information), which relieves the residual stress of the perovskite lattice. [ 57 ] This can be attributed to the source of improving the mechanical stability of F‐PSCs.…”

Multifunctional Two-Dimensional Benzodifuran-Based Polymer for Eco-Friendly Perovskite Solar Cells Featuring High Stability

“…Nevertheless, Spiro-OMeTAD always has to be doped with some ionic additives or p-type dopants to enhance its conductivity and charge carrier mobility. However, due to the hygroscopic nature, those additional doping agents could facilely promote moisture invasion into the perovskite film and cause lead ion leakage, thus impairing the long-term operational stability of PSCs and giving rise to environmental concerns. , Even though encapsulation techniques have been used to enhance the endurance of PSCs to moisture, the intrinsic surface defects and the potentially mismatched energy level of devices still hinder the further development of PSCs. − Therefore, a concurrently protecting perovskite surface with hydrophobic materials passivating those detrimental defects and fine-tuning the energy level alignment of derived devices is profoundly desired to assemble efficient, robust, and lead ion leakage-free PSCs.…”