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Recently, lead‐free Sn‐based perovskite light‐emitting diodes (PeLEDs) have attracted wide attention due to their near‐infrared emission and environmental friendliness. However, desired Sn2+ is easily oxidized to Sn4+ in the crystallization process, resulting in defects and intrinsically p‐doped properties in the perovskite films. The uncontrollable oxidation affects the charge injection balance and radiative recombination, leading to poor device performance. Herein, a bi‐functional conductive molecular, 2,7‐bis(diphenylphosphoryl)‐9,9′‐spirobifluorene (SPPO13) with two P═O functional groups, is used to interact with perovskite to passivate defects and suppress the oxidation of Sn2+. Moreover, the SPPO13 modification layer inserted between the perovskite emitter and the electron transport layer can regulate the carrier injection and transport, thus promoting the charge balance. As a result, the high‐performance near‐infrared CsSnI3 PeLEDs with a record external quantum efficiency (EQE) of 6.60% and ultra‐low efficiency roll‐off are achieved. The work provides a novel approach to regulate defect passivation and charge transport for efficient Sn‐based PeLEDs. [ABSTRACT FROM AUTHOR]

Tin‐based perovskite solar cells (TPSCs) have received great attention due to their eco‐friendly properties and high theoretical efficiencies. However, the fast crystallization feature of tin‐based perovskites leads to poor film quality and limits the corresponding device performance. Herein, a chlorofullerene, C60Cl6, with six chlorine attached to the C60 cage, is applied to modulate the crystallization process and passivate grain boundary defects of the perovskite film. The chemical interactions between C60Cl6 and perovskite components retard the transforming process of precursors to perovskite crystals and obtain a high‐quality tin‐based perovskite film. It is also revealed that the C60Cl6 located at the surfaces and grain boundaries can not only passivate the defects but also offer a role in suturing grain boundaries to suppress the detrimental effects of water and oxygen on perovskite films, especially the oxidation of Sn2+ to Sn4+. As a result, the C60Cl6‐based device yields a remarkably improved device efficiency from 10.03% to 13.30% with enhanced stability. This work provides a new strategy to regulate the film quality and stability of TPSCs using functional fullerene materials. [ABSTRACT FROM AUTHOR]

The non‐radiative recombination at the interfaces of perovskite solar cells (PSCs) is a crucial issue that limits the efficiency and stability of the devices. State‐of‐the‐art surface passivation strategies usually utilize alkyl ammonium halides to suppress the non‐radiative recombination of PSCs, but their high surface reactivity leads to the transformation into 2D perovskites under working conditions, limiting the passivation effect and the charge transport of PSCs. Herein, a non‐halide ionic salt 1‐naphthylmethylammonium formate (NMACOOH) is synthesized for surface passivation of perovskite films. In contrast to the traditional 1‐naphthylmethylammonium iodide, NMACOOH treatment hinders the formation of 2D perovskite and forms a thermally stable PbI2‐NMACOOH adduct on the perovskite surface. Surface characterization reveals that NMA+ can passivate the cation vacancies of the 3D perovskite while HCOO− passivates the metallic Pb0 and halide‐vacancy defects. Therefore, the non‐radiative recombination of PSCs is dramatically suppressed and a high open‐circuit voltage of 1.19 V is obtained. Finally, PSCs with high efficiency of 24.75% and improved long‐term stability (98% of the initial efficiency after 1800‐h storage) are obtained. Moreover, the NMACOOH‐passivated devices also show robust operational stability, retaining 83% of the initial efficiency after working for 658 h under continuous one‐sun illumination. [ABSTRACT FROM AUTHOR]

The under‐coordinated defects within perovskite and its relevant interfaces always attract and trap the free carriers via the electrostatic force, significantly limiting the charge extraction efficiency and the intrinsic stability of perovskite solar cells (PSCs). Herein, self‐diffusion interfacial doping by using ionic potassium L‐aspartate (PL‐A) is first reported to restrain the carrier trap induced recombination via the reconstruction of energy level structure at SnO2/perovskite interface in conventional n‐i‐p structured PSCs. Experiments and theories are consistent with the PL‐A anions that can remain at the SnO2 surface due to strong chemical adsorption. During the spin‐coating of the perovskite film, the cations gradually diffuse into perovskite and endow an n‐doping effect, which provides higher force and a better energy level alignment for the carrier transport. As a result, they obtained 23.74% power conversion efficiency for the PL‐A modified small‐area devices, with dramatically improved open‐circuit voltage of 1.19 V. The corresponding large‐area devices (1.05 cm2) achieved an efficiency of 22.23%. Furthermore, the modified devices exhibited negligible hysteresis and enhanced ambient air stability exceeding 1500 h. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (Pero‐LEDs) with external quantum efficiencies (EQEs) of over 20% have been achieved in the last several years. However, the reproducibility of such high‐efficiency Pero‐LEDs is still low. The perovskite film quality, especially for the non‐radiative defects, is crucial in determining the device performance. These defects may lie in bulk grains, grain boundaries, and interfaces of the as‐formed perovskite films. Here, a polymer infiltrative treatment method is developed to realize effective and universal defect passivation. Specifically, poly(vinylidene fluoride) (PVDF) polymer chains are blended into the perovskite films before they are fully crystallizing. This infiltrative treatment method can regulate crystallization and passivate defects through the chemical interactions of perovskite lattices and PVDF. As a result, high‐quality perovskite films with void‐free surfaces and few‐defect crystals are obtianed. The corresponding Pero‐LEDs show a maximum EQE of 22.29% and an average EQE of 20.44 ± 0.73% based on a statistical analysis of 50 devices, exhibiting excellent reproducibility. The work provides better insights into controlling crystal growth and defect passivation via polymer‐assisted methods for efficient Pero‐LEDs. [ABSTRACT FROM AUTHOR]

Designing functional fullerenes with roles beyond defect passivation and electron‐transporting for perovskite solar cells (PSCs) is essential to the development of fullerenes and PSCs. Here, the authors design and synthesize a functional fullerene, FPD, composed of a C60 cage, a porphyrin ring, and three pentafluorophenyl groups. The structure features of FPD enable it can form chemical interactions with the perovskite lattices. These interactions enhance the defect passivation effect and prevent the decomposition of perovskite under irradiation. As a result, the FPD‐based device yields an improved power conversion efficiency of 23% with substantially enhanced operational stability (T80 > 1500 h). Furthermore, once got damaged, the FPD can prevent lead leakage by forming a stable and water‐insoluble complex (FPD‐Pb). Their findings provide a novel strategy to achieve high‐performance and eco‐friendly PSCs with functional fullerene materials. [ABSTRACT FROM AUTHOR]

It is challenging to passivate defects that are buried in the depth of perovskite films; most of the reported passivation methods cannot reach the deep defects. Herein, methanol is adopted as a dual‐functional reagent to not only act as a solvent but also help the dissolved ions penetrate the depth of perovskite films. By treating the as‐prepared perovskite films with CsBr/methanol solution, Br− ions can react with the undercoordinated Pb2+, and Cs+ ions can fill in the cation vacancies. This strategy enables surface and bulk defects passivation to be achieved simultaneously. The nonradiative recombination of the double‐passivated devices is significantly suppressed and the migration of charged defects is remarkably hindered. As a result, an improved power conversion efficiency of 19.5% and an open‐circuit voltage of 1.183 V is achieved. Moreover, the passivated device can retain ≈80% of the initial efficiency after working for 500 h at maximum power point under 1‐sun illumination, whereas the pristine device reaches 80% of the initial efficiency after only 90 h. This work demonstrates that surface and bulk defects passivation is critical to improve the efficiency and long‐term operational stability of the perovskite solar cells. [ABSTRACT FROM AUTHOR]