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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]

Mixed tin-lead perovskite solar cells have driven a lot of passion for research because of their vital role in all-perovskite tandem solar cells, which hold the potential for achieving higher efficiencies compared to single-junction counterparts. However, the pronounced disparity in crystallization processes between tin-based perovskites and lead-based perovskites, coupled with the easy Sn2+ oxidation, has long been a dominant factor contributing to high defect densities. In this study, we propose a multidimensional strategy to achieve efficient tin-lead perovskite solar cells by employing a functional N-(carboxypheny)guanidine hydrochloride molecule. The tailored N-(carboxypheny)guanidine hydrochloride molecule plays a pivotal role in manipulating the crystallization and grain growth of tin-lead perovskites, while also serving as a preservative to effectively inhibit Sn2+ oxidation, owing to the strong binding between N-(carboxypheny)guanidine hydrochloride and tin (II) iodide and the elevated energy barriers for oxidation. Consequently, single-junction tin-lead cells exhibit a stabilized power conversion efficiency of 23.11% and can maintain 97.45% of their initial value even after 3500 h of shelf storage in an inert atmosphere without encapsulation. We further integrate tin-lead perovskites into two-terminal monolithic all-perovskite tandem cells, delivering a certified efficiency of 27.35%.The disparity in crystallization processes between tin- and lead-based perovskites has been a dominant factor contributing to high defect densities. Here, authors employ a functional molecule to inhibit tin oxidation, realizing monolithic all-perovskite tandems with certified efficiency over 27%. [ABSTRACT FROM AUTHOR]

All-perovskite tandem solar cells hold great promise in surpassing the Shockley–Queisser limit for single-junction solar cells1–3. However, the practical use of these cells is currently hampered by the subpar performance and stability issues associated with mixed tin–lead (Sn–Pb) narrow-bandgap perovskite subcells in all-perovskite tandems4–7. In this study, we focus on the narrow-bandgap subcells and develop an all-in-one doping strategy for them. We introduce aspartate hydrochloride (AspCl) into both the bottom poly(3,4-ethylene dioxythiophene)–poly(styrene sulfonate) and bulk perovskite layers, followed by another AspCl posttreatment. We show that a single AspCl additive can effectively passivate defects, reduce Sn4+ impurities and shift the Fermi energy level. Additionally, the strong molecular bonding of AspCl–Sn/Pb iodide and AspCl–AspCl can strengthen the structure and thereby improve the stability of Sn–Pb perovskites. Ultimately, the implementation of AspCl doping in Sn–Pb perovskite solar cells yielded power conversion efficiencies of 22.46% for single-junction cells and 27.84% (27.62% stabilized and 27.34% certified) for tandems with 95% retention after being stored in an N2-filled glovebox for 2,000 h. These results suggest that all-in-one AspCl doping is a favourable strategy for enhancing the efficiency and stability of single-junction Sn–Pb perovskite solar cells and their tandems.AspCl doping in Sn–Pb perovskite solar cells improves their performance and stability. [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]

This article, published in Advanced Energy Materials, discusses a new synthetic strategy for the development of a family of crystalline fullerene metal halide semiconductors. These semiconductors were used to create highly efficient and stable perovskite solar cells. The study highlights the potential for fully customizable fullerene-based materials for applications beyond photovoltaics. The authors of the article include Wenwen Zheng, Ioannis Spanopoulos, and several other researchers. [Extracted from the article]