24.64%‐Efficiency MA‐Free Perovskite Solar Cell with Voc of 1.19 V Enabled by a Hinge‐Type Fluorine‐Rich Complex

Abstract

High density of defects at interface severely affects the performance of perovskite solar cells (PSCs). Herein, cobalt (II) hexafluoro-2,4-pentanedionat (CoFAc), a hinge-type fluorine-rich complex, is introduced onto the surface of formamidinium cesium lead iodide (FACsPbI 3 ) film to address the issues of perovskite/Spiro-OMeTAD interface. The existence of CoFAc passivates both organic cation and halide anion vacancies by establishing powerful hydrogen bonds with HC(NH 2 ) 2 + (FA + ) and strong ionic bonds with Pb 2+ in perovskite films. In addition, CoFAc serves as a connecting link to enhance interfacial hole-transport kinetics via interacting with Spiro-OMeTAD. Consequently, FACsPbI 3 PSCs with CoFAc modification display a champion power conversion efficiency (PCE) of 24.64% with a charming open-circuit voltage (V OC ) of 1.191 V, which is the record V OC among all the reported organic-inorganic hybrid PSCs with TiO 2 as electron transport layer. Furthermore, CoFAc-modified devices exhibit an outstanding long-term stability, which can maintain 95% of their initial PCEs after exposure to ambient atmosphere for 1500 h without any encapsulation.

Improved Crystallization of Lead Halide Perovskite in Two‐Step Growth Method by Polymer‐Assisted “Slow‐Release Effect”

“…Considering the molecule structure of FAI and PAA, the interaction should be existing between groups of "-C=O" and "FA+," in addition, "hydrogen bond" might appear due to the static electrical force. [32][33][34] Such interaction could hinder the diffusion of organic cations into the PbI 2 matrix, and lower down the reaction between them. As a result, it is more difficult for the coated film to turn black.…”

Surface Passivation of CsPbI 3 Films for Efficient and Stable Hole-Transporting Layer-Free Carbon-Based Perovskite Solar Cells

“…But for the commercial application of PSCs, long-term stability is as equally important as device efficiency. Till now, highly efficient PSCs are based on organic–inorganic hybrid perovskites, which consist of thermolabile organic cations (e.g., methylammonium (MA), formamidinium (FA)), hindering their further development for commercialization. − To address this issue, inorganic perovskites employing Cs + as an A-site cation are developed, which have been demonstrated to be an efficient component for constructing highly efficient PSCs. − Among all of the reported inorganic perovskites, the CsPbI 3 perovskite possesses a suitable band gap ( E g : ∼1.7 eV) as well as decent phase stability and is considered as the most promising candidate for commercial application. − Actually, the PCE of the best-performing CsPbI 3 -based PSCs has exceeded 21% and is in a rapid growth stage currently. , …”

Synergistic Defect Passivation and Crystallization Modulation in Efficient Perovskite Solar Cells: The Case of Multifunctional 2-Anisidine-4-Sulfonic Acid

“…Defects at surface and GBs not only lead to nonradiative charge recombination and ion migration but also accelerate external moisture infiltration, causing the decomposition of perovskite films. , Considering that the long-term stability is a huge obstacle to the commercial application of PSCs, the humidity stability of the perovskite films and relevant devices was also investigated. Resistance to water erosion of the perovskite films before and after 2A4SA doping exposed to the ambient atmosphere (20–30 °C and 20–60% RH) was monitored by XRD (Figure a), and the optical photographs of the perovskite films in aging on different days were tracked, as shown in Figure b.…”

“…As the most crucial functional layer in PSCs, the perovskite light-absorbing layer is key in determining the photovoltaic performance of the ultimate device. However, due to the soft ionic crystal nature of perovskite itself and its uncontrollable rapid crystallization in low-temperature solution fabrication process, , abundant adverse defects including uncoordinated Pb 2+ , cation vacancies and halide ionic defects will inevitably appear on the perovskite surface and grain boundaries (GBs), − thus irregular-aligned orientations of the perovskite crystal grains. Worse still, these defects sites as nonradiative recombination centers can not only provide pathways for external water and oxygen erosion, inducing the irreversible degradation of film and corresponding device, but also aggravate nonradiative recombination and ion migration, resulting in distinctly decreased open-circuit voltage ( V oc ) and fill factor (FF) …”