and modifying the charge transporting layers (CTLs), yet the interfacial mismatch between perovskite and CTLs is a non-negligible issue that dominates the efficiency and stability of corresponding devices. [7][8][9][10][11] Nickel oxide (NiO x ) nanocrystals as a promising stable hole transporting layer (HTL) in inverted p-i-n PVSCs are less prone to hysteresis and work well with flexible or tandem architectures. [12] Nevertheless, the PCE of NiO x -based inverted devices are usual inferior to the organic regular counterparts owing to the several interfacial issues: i) abundant surface traps and mismatch energy level restrict the charge carrier extraction, causing large energy offset; [13] ii) the redox reaction between Ni 3+ and A-site cation salts form a PbI 2 -rich hole extraction barrier, leading to severe interfacial destruction; [14] iii) inconsistent thermal expansion of lattice units in NiO x and perovskite results in tensile strain, prejudicing the microstructure and accelerating the degradation of perovskite. [15][16][17] Therefore, it is urge to solve these issues for performance enhancement and commercialization application of NiO x -based PVSCs.Recently, a great deal of molecular interlayers have been applied to passivate or adjust the energy level of NiO x /perovskite interface for strengthen the efficiency and stability in p-i-n devices, such as inorganic salts, [18][19][20] acids, [21] fullerene derivatives [22] and polymers buffer layer. [23][24][25] Nevertheless, most of the buffer layers are nonconductive and accompanied with the uncontrollable thickness and uniformity, which undoubtedly affect the optimization of charge transfer and perovskite crystal growth. Relatively speaking, the self-assembled small-molecule (SASM) can form thermodynamically favored ordered self-assembled layer that has been extensively proved as effective modifier to modulate the energy level and surface chemical state, as well as enhance the affinities of the deposition layer and substrate. [26] For instance, Fang et al. has reported that a polar chlorine-terminated SASM can modulate the energy-level alignment by forming a dipole moment at the interface. [27] Chen et al. has regulated the crystalline process and optimized the morphology of perovskite film by using 3-aminopropanioc acid SASM modified titanium oxide. [28] Other SASMs with different chemical terminations (such as amines, [29] carboxylates, [30] thiols, [31] and phosphonic acid [32] ) are also demonstrated to dramatically modify the electron Interfacial lattice mismatch and adverse reaction are the key issues hindering the development of nickel oxide (NiO x )-based inverted perovskite solar cells (PVSCs). Herein, a p-chlorobenzenesulfonic acid (CBSA) self-assembled small-molecule (SASM) is adopted to anchor NiO x and perovskite crystals to endow dual-passivation. The chlorine terminal of SASMs can provide growth sites for perovskite, leading to interfacial strain release. Meanwhile, the sulfonic acid group from SASMs can passivate surface defects of NiO x ,...

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Tin-based perovskite solar cells (PVSCs) are regarded as the most promising alternative among lead-free PVSCs. However, the rapid crystallization for tin-based perovskite tends to cause inferior film morphology and abundant defect states, which make poor photovoltaic performance. Here, 1-butyl-3-methylimidazolium bromide (BMIBr) ionic liquids (ILs) with strong polarity and a low melting point are first employed to produce the Ostwald ripening effect and obtain high-quality tin-based perovskite films with a large grain size. Meanwhile, the non-radiative recombination ascribed from defect states can also be effectively reduced for BMIBr-treated perovskite films. Consequently, a photoelectric conversion efficiency (PCE) of 10.09% for inverted tin-based PVSCs is attained by the Ostwald ripening effect. Moreover, the unencapsulated devices with BMIBr retain near 85% of the original PCE in a N 2 glovebox beyond 1200 h and about 40% of the original PCE after exposure to air for 48 h.

Transition-metal carbides (MXenes) are an emerging class of two-dimensional (2D) materials with promising electrochemical sensing performance due to their unique structural and electronic properties. To further improve its sensing performance, herein, the composite of Ti 3 C 2 T x (MXene) and electrochemically reduced graphene oxide (MXene/ERGO) was proposed as electrode material for electrochemical detection of pesticide carbendazim (CBZ). The MXene/ERGO was synthesized by a facile and green electrochemical approach, where the mixture of MXene and graphene oxide (GO) was firstly dropped on the electrode surface, followed by electrochemical reduction of GO. The ERGO conductive networks tightly linked the separated layers of Ti 3 C 2 T x and connected the separated Ti 3 C 2 T x particles, which leading to enhanced electronic conductivity, improved the electrochemical reactivity of electrode materials and facilitated electron transfer between electrode and detection molecules. Consequently, the sensor based on MXene/ERGO exhibited a high sensitive detection of CBZ with a wide linear range of 2.0 nM ∼ 10.0 μM and a low limit of detection (LOD) of 0.67 nM. Moreover, the sensor showed good selectivity and reproducibility toward CBZ detection. The proposed sensor was successfully subjected to detect CBZ in cucumber and orange juice samples with acceptable results.

Perovskite polycrystalline films contain numerous intrinsic and interfacial defects ascribed to the solution preparation process, which are harmful to both the photovoltaic performance and the stability of perovskite solar cells (PVSCs). Although various passivators have been proved to be promising materials for passivating perovskite films, there is still a lack of deeper understanding of the effectiveness of the different passivation methods. Here, the mechanism between antisolvent dripping and additive doping strategies on the passivation effects in PVSCs is systematically investigated with a nonfullerene small molecule (F8IC). Such a passivated effect of F8IC is realized via coordination interactions between the carbonyl (CO) and nitrile (C−N) groups of F8IC with Pb 2+ ion of MAPbI 3 . Interestingly, F8IC antisolvent dripping can effectively passivate the surface defects and thus inhibit the nonradiative charge recombination on the upper part of the perovskite layer, whereas F8IC additive doping significantly reduces the surface and bulk defects and produces a compact perovskite film with denser crystal grains, thus facilitating charge transmission and extraction. Therefore, these benefits are translated into significant improvements in the short-circuit current density (J sc ) to 21.86 mA cm −2 and a champion power conversion efficiency of 18.40%. The selection of an optimal passivation strategy should also be considered according to the energy level matching between the passivators and the perovskite. The large energetic disparity is unsuitable for additive doping, whereas it is expected in antisolvent dripping.

The electron transport layer (ETL) plays a crucial part in extracting electron carriers while optimizing the interfacial contact of perovskite/electrode in planar heterojunction perovskite solar cells (PVSCs). Despite various ETLs being designed for efficient PVSCs, there exists hardly any research on the effect of molecular stacking order on device performance. Herein, poly(ethylene-covinyl acetate) (EVA) is employed as the [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) solution additive. The strong binding energy between EVA with PC 61 BM promotes the molecular stacking order of ETLs, which alleviates the morphology inhomogeneity, possesses a matched energy level, blocks ion migration, and improves the water-oxygen barrier of perovskite devices. The blade-coated MAPbI 3 -based PVSCs achieve a power conversion efficiency (PCE) of 19.32% with positive reproducibility and negligible hysteresis, as well as maintain 90% and 80% of the initial PCE after storage under inert and ambient conditions (52% humidity) for 1500 h without encapsulation. This strategy also improves the champion PCE of CsFAMA-based PVSCs to 20.33%. These findings demonstrate that the regulation of molecular stacking order is a valid approach to optimize interfacial charge-carrier recombination in PVSCs, which meet the demand for high-performance ETL in large-area PVSCs and improve the upscaling of the fabrication technology toward practical applications.

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