Deposition of perovskite films by antisolvent engineering is a highly common method employed in perovskite photovoltaics research. Herein, we report on a general method that allows for the fabrication of highly efficient perovskite solar cells by any antisolvent via manipulation of the antisolvent application rate. Through detailed structural, compositional, and microstructural characterization of perovskite layers fabricated by 14 different antisolvents, we identify two key factors that influence the quality of the perovskite layer: the solubility of the organic precursors in the antisolvent and its miscibility with the host solvent(s) of the perovskite precursor solution, which combine to produce rate-dependent behavior during the antisolvent application step. Leveraging this, we produce devices with power conversion efficiencies (PCEs) that exceed 21% using a wide range of antisolvents. Moreover, we demonstrate that employing the optimal antisolvent application procedure allows for highly efficient solar cells to be fabricated from a broad range of precursor stoichiometries.

photovoltaic technology, where lifetimes greater than 25 years are required. [2] Although the issue of device stability has attracted increased attention of the photovoltaic research community in the last two years, reports that systematically study the fundamental causes (e.g., heat, electrical stress, humidity, oxygen, (UV) light, chemical precursors, processing conditions, influence of film quality and morphology) and mechanisms limiting the material and device stability remain scarce. [2][3][4][5] While the degradation of methylammonium lead iodide (MAPbI 3 ) in humid air has been studied experimentally as well as theoretically and was long thought to be the main factor for material degradation in ambient environment, [6][7][8][9][10][11][12][13][14][15] studies exploring the influence of oxygen and light on the solar cell performance have only recently been reported. [16][17][18][19][20] It has been shown that photoexcited electrons in the perovskite layer can form superoxide (O 2 − ) via electron transfer to molecular oxygen, which through deprotonation of the methylammonium cation in turn results in irreversible material degradation. The severity of the degradation has been linked to the efficiency of electron extraction via the electron extracting layer (EEL): devices employing a compact-TiO 2 /mesoporous Al 2 O 3 or compact-TiO 2 as EELs degraded in dry air on a timescale of less than 1 h, while with the use of a mesoporous TiO 2 layer, an EEL which results in faster electron extraction, the lifetimes were significantly increased. However, in these reports only the degradation of complete photovoltaic device was reported, with limited information on the degradation of the perovskite active layer itself and the impact of its microstructure was not identified.In this work, we systematically study the degradation of MAPbI 3 films under precisely controlled exposure to various oxygen levels (0-20%) under simulated sunlight in order to shed light on the progression of perovskite degradation under these conditions. We investigate two types of perovskite layers that are formed using different fabrication methods. The two recipes allow us to include the effect of layer microstructure on the dynamics of oxygen-induced degradation. We characterize the electronic, optical, compositional, and structural properties of the degraded perovskite films and correlate these results This paper investigates the impact of microstructure on the degradation rate of methylammonium lead triiodide (MAPbI 3 ) perovskite films upon exposure to light and oxygen. By comparing the oxygen induced degradation of perovskite films of different microstructure-fabricated using either a lead acetate trihydrate precursor or a solvent engineering technique-it is demonstrated that films with larger and more uniform grains and better electronic quality show a significantly reduced degradation compared to films with smaller, more irregular grains. The effect of degradation on the optical, compositional, and microstructural properties of the perovsk...

Transferring the high power conversion efficiencies (PCEs) of spin‐coated perovskite solar cells (PSCs) on the laboratory scale to large‐area photovoltaic modules requires a significant advance in scalable fabrication methods. Digital inkjet printing promises scalable, material, and cost‐efficient deposition of perovskite thin films on a wide range of substrates and in arbitrary shapes. In this work, high‐quality inkjet‐printed triple‐cation (methylammonium, formamidinium, and cesium) perovskite layers with exceptional thicknesses of >1 µm are demonstrated, enabling unprecedentedly high PCEs > 21% and stabilized power output efficiencies > 18% for inkjet‐printed PSCs. In‐depth characterization shows that the thick inkjet‐printed perovskite thin films deposited using the process developed herein exhibit a columnar crystal structure, free of horizontal grain boundaries, which extend over the entire thickness. A thin film thickness of around 1.5 µm is determined as optimal for PSC for this process. Up to this layer thickness X‐ray photoemission spectroscopy analysis confirms the expected stoichiometric perovskite composition at the surface and shows strong deviations and inhomogeneities for thicker thin films. The micrometer‐thick perovskite thin films exhibit remarkably long charge carrier lifetimes, highlighting their excellent optoelectronic characteristics. They are particularly promising for next‐generation inkjet‐printed perovskite solar cells, photodetectors, and X‐ray detectors.

Polyphenols, the phenolic hydroxyl group-containing organic molecules, are widely found in natural plants and have shown beneficial effects on human health. Recently, polyphenol-containing nanoparticles have attracted extensive research attention due to their antioxidation property, anticancer activity, and universal adherent affinity, and thus have shown great promise in the preparation, stabilization, and modification of multifunctional nanoassemblies for bioimaging, therapeutic delivery, and other biomedical applications. Additionally, the metal−polyphenol networks, formed by the coordination interactions between polyphenols and metal ions, have been used to prepare an important class of polyphenol-containing nanoparticles for surface modification, bioimaging, drug delivery, and disease treatments. By focusing on the interactions between polyphenols and different materials (e.g., metal ions, inorganic materials, polymers, proteins, and nucleic acids), a comprehensive review on the synthesis and properties of the polyphenol-containing nanoparticles is provided. Moreover, the remarkable versatility of polyphenol-containing nanoparticles in different biomedical applications, including biodetection, multimodal bioimaging, protein and gene delivery, bone repair, antibiosis, and cancer theranostics is also demonstrated. Finally, the challenges faced by future research regarding the polyphenol-containing nanoparticles are discussed.

Fenton reaction‐mediated chemodynamic therapy (CDT) can kill cancer cells via the conversion of H2O2 to highly toxic HO•. However, problems such as insufficient H2O2 levels in the tumor tissue and low Fenton reaction efficiency severely limit the performance of CDT. Here, the prodrug tirapazamine (TPZ)‐loaded human serum albumin (HSA)–glucose oxidase (GOx) mixture is prepared and modified with a metal–polyphenol network composed of ferric ions (Fe3+) and tannic acid (TA), to obtain a self‐amplified nanoreactor termed HSA–GOx–TPZ–Fe3+–TA (HGTFT) for sustainable and cascade cancer therapy with exogenous H2O2 production and TA‐accelerated Fe3+/Fe2+ conversion. The HGTFT nanoreactor can efficiently convert oxygen into HO• for CDT, consume glucose for starvation therapy, and provide a hypoxic environment for TPZ radical‐mediated chemotherapy. Besides, it is revealed that the nanoreactor can significantly elevate the intracellular reactive oxygen species content and hypoxia level, decrease the intracellular glutathione content, and release metal ions in the tumors for metal ion interference therapy (also termed “ion‐interference therapy” or “metal ion therapy”). Further, the nanoreactor can also increase the tumor’s hypoxia level and efficiently inhibit tumor growth. It is believed that this tumor microenvironment‐regulable nanoreactor with sustainable and cascade anticancer performance and excellent biosafety represents an advance in nanomedicine.

Grasping the fundamentals of graphene growth is vital for graphene synthesis. By employing classical molecular dynamics with the ReaxFF potential, we have investigated the evolution of carbon structures and the growth kinetics of graphene on Ni(111) surface at different temperatures. Our results showed that low C concentration leads to the dissolution of C atoms into Ni only, whereas high C concentration leads to the formation of graphene island. By efficient defect annealing at the optimal temperature of ∼1000 K, the quality of graphene island can be significantly improved. Furthermore, a graphene island can grow larger by capturing the deposited C atoms and form more hexagons on the edge with its self-healing capability during the growth. These underlying observations and understandings are instructive for the control of the CVD growth of graphene.

Perovskite-based solar cells are promising because of their rapidly improving efficiencies but suffer from instability issues. Recently, it has been claimed that one of the key contributors to the instability of perovskite solar cells is ion migration-induced electrode degradation, which can be avoided by incorporating inorganic hole-blocking layers (HBLs) in the device architecture. In this work, we investigate the operational environmental stability of methylammonium lead iodide perovskite solar cells that contain either an inorganic or organic HBL, with only the former effectively blocking ions from migrating to the metal electrode. This is confirmed by X-ray photoemission spectroscopy measured on the electrodes of degraded devices, where only electrodes of devices with an organic HBL show a significant iodine signal. Despite this, we show that when these devices are degraded under realistic operational conditions (i.e., constant illumination in a variety of atmospheric conditions), both types of devices exhibit nearly identical degradation behavior. These results demonstrate that contrary to prior suggestions, ion-induced electrode degradation is not the dominant factor in perovskite environmental instability under operational conditions.

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