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Buried interface modification can effectively improve the compatibility between interfaces. Given the distinct interface selections in perovskite solar cells (PSCs), the applicability of a singular modification material remains limited. Consequently, in response to this challenge, we devised a tailored molecular strategy based on the electronic effects of specific functional groups. Therefore, we prepared three distinct silane coupling agents, and due to the varying inductive effects of these functional groups, the electronic distribution and molecular dipole moments of the coupling agents are correspondingly altered. Among them, trimethoxy (3,3,3‐trifluoropropyl)‐silane (F3‐TMOS), which possesses electron‐withdrawing groups, generates a molecular dipole moment directed toward the hole transport layer (HTL). This approach changes the work function of the HTL, optimizes the energy level alignment, reduces the open‐circuit voltage loss, and facilitates carrier transport. Furthermore, through the buffering effect of the coupling agent, the interface strain and lattice distortion caused by annealing the perovskite are reduced, enhancing the stability of the tin‐based perovskite. Encouragingly, tin PSCs treated with F3‐TMOS achieved a champion efficiency of 14.67 %. This strategy provides an expedient avenue for the design of buried interface modification materials, enabling precise molecular adjustments in accordance with distinct interfacial contexts to ameliorate mismatched energetics and enhance carrier dynamics. [ABSTRACT FROM AUTHOR]

The substrates of conventional flexible perovskite solar cells (FPSCs) are thermoplastic polymer material polyethylene naphthalate (PEN), which will deform during high temperature annealing process. In addition, lead iodide (PbI2) permanently formed and the substrate undergoes reversible deformation from 20 °C to 200 °C and back to 20 °C. Therefore, to balance the substrate supporting capacity and the crystalline quality of narrow band gap α‐phase formamidinium lead iodide (α‐FAPbI3), an annealing process of 120 °C for 30 minutes is determined. Additionally, there will also be a large number of gaps and lattice strain at the perovskite grain boundaries during the annealing process as the FAPbI3 phase transition is accompanied by much lattice shrinkage. As a result, 1,6‐hexanediammonium diiodide (HADI) is chosen to passivate the defects and release the stress of perovskite film. Therefore, a recorded 1.4% extended stretch rate of the flexible film is attained. Finally, the champion PCE of 21.14% under AM 1.5G and 31.52% under 1062 lux is achieved after HADI treatment, accompanied by a better long‐term and mechanical stability. This study provides annealing process optimization and stress relief strategies for the further development of narrow band gap FPSCs. [ABSTRACT FROM AUTHOR]

State‐of‐the‐art, high‐performance formamidinium‐lead‐iodide‐based (FAPbI3‐based) perovskite photovoltaics are mainly prepared by one‐step antisolvent dripping deposition or two‐step sequential fabrication methods. Compared with the one‐step deposition, the two‐step fabricated perovskite films tend to grow columnar perovskite grains vertically which is easier for carrier extraction and transportation. Herein, the concept of formamidinium methylammonium cesium based ternary‐cation two‐step sequential deposition method is put forward by incorporating cesium acetate (CsAc) into a lead iodide precursor, which generates CsPbI3 crystal nuclei improving the further perovskite crystallization. When the formamidinium/methylammonium‐based organic amine salts solution is spin coated on the PbI2 substrate, the acetate moves upward and induces perovskite orientational and uniform crystallization, which can go a step further for the vertical columnar grains achieving fewer defects and higher photovoltaic efficiency. The champion outdoor power conversion efficiency of the modified device under AM 1.5G reaches 21.50% and its indoor efficiency at 1000 lux reaches 40.99%. This work paves the way for further exploring ternary‐cation two‐step sequential deposition methods to prepare high‐performance perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

The effective utilization of self‐assembled monolayers (SAMs) has indeed resulted in significant improvement in the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs). However, the poor interface contact between self‐assembled monolayer (SAM) and perovskite layers limits the further improvement of inverted PSCs. Herein, polyaniline is employed as a conductive adhesive, enabling interaction with the perovskite and simultaneous coupling with the SAM, to optimize the buried interface contact. Furthermore, the adhesive strategy is validated to alleviate residual tensile strain at the buried interface using the non‐destructive back grazing‐incidence wide‐angle X‐ray scattering (BGIWAXS) technique. As a result, the optimized inverted PSCs achieve a champion PCE of 25.59% with impressive stability by retaining 97.3% of its initial efficiency after 1200 h under ambient conditions and light‐emitting diode illumination. The findings provide a facial adhesive bridging strategy to play more impressive functions in the SAM‐based inverted PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • KSCN was introduced as multifunctional layer in tin perovskite photovoltaics. • KSCN functioned as suppressed antioxidation and perovskite crystallization. • The target device presented an outdoor efficiency of 11.17% under AM 1.5G. • The target device delivered an indoor efficiency of 17.57% under 1062 lx. Serious issues such as easy-oxidation of Sn2+, fast crystallization rate and high defect density are still existing in tin perovskites to restrain their photovoltaic performance. Herein, a strategy of bottom passivation by potassium thiocyanate (KSCN) has been developed in FA 0.75 MA 0.25 SnBrI 2 -based perovskite solar cells. KSCN interlayer exhibited multifunctional roles in aligning energy levels, assisting perovskite crystallization and promoting charge transport. The resulting champion device delivered superior power conversion efficiency (PCE) as high as 11.17% under AM 1.5G illumination. It is worth noting that the champion indoor photovoltaics efficiency under 2956 K@1062 lx (334.41 μW/cm2) illumination could approach 17.57%, which is the highest PCE for tin perovskite photovoltaics to our knowledge. The outstanding indoor performance demonstrates the huge application potential of eco-friendly tin perovskites. [ABSTRACT FROM AUTHOR]