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Achieving high‐performance perovskite solar cells hinges on the precise management of interfacial properties. However, the current research predominantly concentrates on addressing individual interfaces, often overlooking the potential synergies between the upper and lower interfaces crucial for efficient carrier transfer. Herein, an effective interfacial strategy is introduced, which combines 2‐aminoterephthalic acid (2‐AA) pre‐processing with post‐processing techniques to prepare superior mixed tin‐lead perovskite films suitable for both single‐junction and all‐perovskite tandem solar cells. Incorporating 2‐AA at both the upper and lower interfaces of the perovskite films serves to regulate interfacial defects, alleviate interface residual stress, and improve film crystallinity. In addition, the 2‐AA molecule acts as an interface protective layer, anchoring tin and lead atoms, facilitating band energy alignment, and improving film and device stability. As a result, mixed tin‐lead perovskite solar cells achieved an improved open‐circuit voltage of 0.87 V and PCE of 21.57%. Furthermore, the integration of these optimized tin‐lead perovskite subcells into four‐terminal all‐perovskite tandem solar cells yielded an impressive efficiency of 27.46%. This work thus offers an effective strategy for comprehensive interfacial engineering and stress relief, paving the way for the production of high‐performance perovskite solar cells (PSCs). [ABSTRACT FROM AUTHOR]

Despite advances in mixed tin‐lead (Sn‐Pb) perovskite‐based solar cells, achieving both high‐efficiency and long‐term device stability remains a major challenge. Current device deficiencies stem partly from inefficient carrier transport, originating from defects and improper band energy alignment among the device's interfaces. Developing multifunctional interlayer materials simultaneously addressing the above concerns poses an excellent strategy. Herein, through molecular and crystal engineering, an amine‐functionalized C60 mono‐adduct derivative (C60‐2NH3 = bis(2‐aminoethyl) malonate‐C60) is utilized for the synthesis of the first crystalline fullerene‐based 2D metal halide semiconductor, namely (C60‐2NH3)Pb2I6. Single crystal XRD studies elucidated the structure of the new material, while DFT calculations highlighted the strong contribution of C60‐2NH3 to the electronic density of states of the conduction band of (C60‐2NH3)Pb2I6. Utilization of C60‐2NH3 as an interlayer between a FA0.6MA0.4Pb0.7Sn0.3I3 perovskite and a C60 layer offered superior band energy alignment, reduced nonradiative recombination, and enhanced carrier mobility. The corresponding perovskite solar cell (PSC) device achieved a power conversion efficiency (PCE) value of 21.64%, maintaining 90% of its initial efficiency, after being stored under a N2 atmosphere for 2400 h. This work sets the foundation for developing a new family of functional materials, namely Fullerene Metal Halide Semiconductors, targeting applications from photovoltaics to catalysis, transistors, and supercapacitors. [ABSTRACT FROM AUTHOR]

Tin (Sn)-based perovskites are very promising for the fabrication of low-toxicity lead-free perovskite solar cells (PSCs), but they suffer from easy oxidation of Sn2+ to Sn4+ which leads to poor performance. Herein, we report a facile solution method for the purification of SnI2 in Sn-based PSCs by toluene washing. We found that toluene can dissolve undesired SnI4 and retain the SnI2 source, which enabled us to fabricate efficient Sn-based PSCs with much-reduced harmful Sn4+ impurities. The as-prepared formamidinium tin iodide perovskite films have markedly improved film morphology, enhanced crystalline quality, increased carrier lifetime, etc. Ultimately, the best-performing solar cell obtained using toluene-purified SnI2 precursors delivers a promising power conversion efficiency of 10.70% and the efficiency even increases to 11.06% after nearly one month of storage in an N2 atmosphere. This work paves a facile way for overcoming the complicated purification of SnI2 for efficient Sn-based PSCs. [ABSTRACT FROM AUTHOR]

Tin halide perovskite solar cells (TPSCs) have attracted extensive attention because of their low toxicity and high theoretical efficiency. However, rapid crystallization, rich defects, and easy oxidation of tin‐based perovskite films seriously restrict solar cell performance. Herein, a composition and additive engineering solution by removing commonly used tin fluoride additive from formamidinium tin triiodide perovskite precursors and replacing it with excess tin (II) iodide and ethylenediamine dihydroiodide (EDAI2) is adopted. The presence of EDAI2 and excess SnI2 and the absence of SnF2 enable tin‐based perovskite films with greatly improved morphology, enhanced crystalline quality, boosted optical properties, and prolonged carrier lifetime. Therefore, the SnF2‐free non‐stoichiometric TPSCs employing the EDAI2 additive and excess SnI2 have increased built‐in potential, lowered dark currents, and reduced carrier recombination. The resulting SnF2‐free and SnI2‐rich TPSCs with EDAI2 addition realize a steady‐state efficiency of 10.0%, which is one of the highest power conversion efficiencies among the SnF2‐free TPSCs, along with considerably improved light stability. This work highlights the crucial roles of additives in TPSCs and provides an effective strategy to fabricate efficient and stable low‐toxic lead‐free perovskite solar cells. [ABSTRACT FROM AUTHOR]

Mixed tin–lead (Sn–Pb) perovskites often face a daunting challenge: rapid and uncontrollable crystallization, leading to a plethora of defects and significant stress. This issue is particularly exacerbated during the blade‐coating preparation of scalable Sn–Pb perovskite films. In this study, a facile strategy involving the addition of ammonium citrate (AC) to narrow‐bandgap mixed Sn–Pb perovskite precursors is introduced. AC, armed with its arsenal of multiple carboxyl and amino groups, acts as a virtuoso conductor, orchestrating controlled crystal growth by harmonizing with Pb2+ and Sn2+ ions. This addition significantly boosts the crystallinity of the perovskite films, alleviates interface stress, inhibits Sn2+ oxidation, and mitigates interfacial defects. Consequently, The blade‐coated AC‐incorporated mixed Sn–Pb perovskite solar cells achieve a high photovoltaic conversion efficiency of nearly 21%. Furthermore, extending this strategy to two‐terminal all‐perovskite tandem solar cells yielded a remarkable maximum efficiency of 27.20%. This work presents an effective strategy for producing efficient blade‐coated mixed Sn–Pb perovskite solar cells, heralding a pathway toward scalable fabrication of all‐perovskite tandem solar cells. [ABSTRACT FROM AUTHOR]

Tin‐lead (Sn‐Pb) mixed perovskite solar cells (PSCs), which serve as bottom subcells in all‐perovskite tandem solar cells, are pivotal for developing highly efficient solar cells. However, the vulnerability of stannous (Sn2+) to spontaneous oxidation to harmful tetravalent tin (Sn4+) presents significant challenges. Here, a “mouse glue trap” strategy is proposed to mitigate this issue by introducing a multifunctional additive, oxamidic acid potassium salt (OAPS). This approach effectively traps undesired Sn4+ impurities through strong interactions between the oxaminic acid groups of OAPS and Sn4+ impurities. Additionally, OAPS, with its unique functional groups, can inhibit Sn2+ oxidation, passivate defects, alleviate stress, and improve crystalline quality in Sn‐Pb mixed perovskite films. As a result, the enhanced Sn‐Pb mixed narrow‐bandgap PSCs incorporating OAPS achieve a power conversion efficiency of 22.04% and exhibit improved storage stability, with 91% retention after 3072 h of storage in an N2‐filled glovebox. Moreover, all‐perovskite tandem cells using OAPS‐incorporated Sn‐Pb narrow‐bandgap PSCs as subcells demonstrate efficiencies of 27.17% and 28.31% for two‐terminal and four‐terminal tandems, respectively, presenting a straightforward approach to optimizing performance in Sn‐Pb mixed PSCs and their tandems. [ABSTRACT FROM AUTHOR]