Communication-Efficient Nonparametric Quantile Regression via Random Features

This paper introduces a refined algorithm designed for distributed nonparametric quantile regression in a reproducing kernel Hilbert space (RKHS). Unlike existing nonparametric approaches that primarily address homogeneous data, our approach utilizes kernel-based quantile regression to effectively model heterogeneous data. Moreover, we integrate the concepts of random features (RF) and communication-efficient surrogate likelihood (CSL) to ensure accurate estimation and enhance computational efficiency in distributed settings. Specifically, we employ an embedding technique to map the original data into RF spaces, enabling us to construct an extended surrogate loss function. This function can be locally optimized using an iterative alternating direction method of multipliers (ADMM) algorithm, minimizing the need for extensive computation and communication within the distributed system. The paper thoroughly investigates the asymptotic properties of the distributed estimator and provides convergence rates of the excess risk. These properties are established under mild technical conditions and are comparable to state-of-the-art results in the literature. Additionally, we validate the effectiveness of the proposed algorithm through a comprehensive set of synthetic examples and a real data study, effectively highlighting its advantages and practical utility.</p

CsPb_0.9Sn_0.1IBr₂ Based All-Inorganic Perovskite Solar Cells with Exceptional Efficiency and Stability

The emergence of perovskite solar cells (PSCs) has generated enormous interest in the photovoltaic research community. Recently, cesium metal halides (CsMX₃, M = Pb or Sn; X = I, Br, Cl or mixed halides) as a class of inorganic perovskites showed great promise for PSCs and other optoelectronic devices. However, CsMX₃-based PSCs usually exhibit lower power conversion efficiencies (PCEs) than organic–inorganic hybrid PSCs, due to the unfavorable band gaps. Herein, a novel mixed-Pb/Sn mixed-halide inorganic perovskite, CsPb_0.9Sn_0.1IBr₂, with a suitable band gap of 1.79 eV and an appropriate level of valence band maximum, was prepared in ambient atmosphere without a glovebox. After thoroughly eliminating labile organic components and noble metals, the all-inorganic PSCs based on CsPb_0.9Sn_0.1IBr₂ and carbon counter electrodes exhibit a high open-circuit voltage of 1.26 V and a remarkable PCE up to 11.33%, which is record-breaking among the existing CsMX₃-based PSCs. Moreover, the all-inorganic PSCs show good long-term stability and improved endurance against heat and moisture. This study indicates a feasible way to design inorganic halide perovskites through energy-band engineering for the construction of high-performance all-inorganic PSCs

Interface Engineering of Anchored Ultrathin TiO₂/MoS₂ Heterolayers for Highly-Efficient Electrochemical Hydrogen Production

An efficient self-standing hydrogen evolution electrode was prepared by in situ growth of stacked ultrathin TiO₂/MoS₂ heterolayers on carbon paper (CP@TiO₂@MoS₂). Owing to the high overall conductivity, large electrochemical surface area and abundant active sites, this novel electrode exhibits an excellent performance for hydrogen evolution reaction (HER). Remarkably, the composite electrode shows a low Tafel slope of 41.7 mV/dec, and an ultrahigh cathodic current density of 550 mA/cm² at a very low overpotential of 0.25 V. This work presents a new universal strategy for the construction of effective, durable, scalable, and inexpensive electrodes that can be extended to other electrocatalytic systems

Interface Engineering of Anchored Ultrathin TiO₂/MoS₂ Heterolayers for Highly-Efficient Electrochemical Hydrogen Production

An efficient self-standing hydrogen evolution electrode was prepared by in situ growth of stacked ultrathin TiO₂/MoS₂ heterolayers on carbon paper (CP@TiO₂@MoS₂). Owing to the high overall conductivity, large electrochemical surface area and abundant active sites, this novel electrode exhibits an excellent performance for hydrogen evolution reaction (HER). Remarkably, the composite electrode shows a low Tafel slope of 41.7 mV/dec, and an ultrahigh cathodic current density of 550 mA/cm² at a very low overpotential of 0.25 V. This work presents a new universal strategy for the construction of effective, durable, scalable, and inexpensive electrodes that can be extended to other electrocatalytic systems

All-Inorganic Perovskite Solar Cells

The research field on perovskite solar cells (PSCs) is seeing frequent record breaking in the power conversion efficiency (PCE). However, organic–inorganic hybrid halide perovskites and organic additives in common hole-transport materials (HTMs) exhibit poor stability against moisture and heat. Here we report the successful fabrication of all-inorganic PSCs without any labile or expensive organic components. The entire fabrication process can be operated in ambient environment without humidity control (e.g., a glovebox). Even without encapsulation, the all-inorganic PSCs present no performance degradation in humid air (90–95% relative humidity, 25 °C) for over 3 months (2640 h) and can endure extreme temperatures (100 and −22 °C). Moreover, by elimination of expensive HTMs and noble-metal electrodes, the cost was significantly reduced. The highest PCE of the first-generation all-inorganic PSCs reached 6.7%. This study opens the door for next-generation PSCs with long-term stability under harsh conditions, making practical application of PSCs a real possibility