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En-echelon joints are common in rocky slopes and faults, and their instability seriously threatens the safety of geotechnical engineering. Filling and reinforcing en-echelon joints in slopes is highly important for maintaining the safety of engineering and human beings. In view of this, this study aims to investigate the fracture behavior of en-echelon joints after filling and reinforcing to provide a reference for the filling and reinforcing work of slopes In this study, en-echelon gabbro samples with different crack angles were filled with cement slurry, a compression test was subsequently conducted, and the loading process was monitored via acoustic emission technology. The results showed that the compressive strength of the specimens after cementing the joints is increased by more than 30%, the compressive strength of the specimens with a β of 15°increased by up to 59%, and the stability of the specimens significantly improved. The shear failure of the filled and unfilled samples was the main failure at the peak load. There were two failure modes for the samples with different crack angles. The small dip angle samples were lightly broken, and the main cracks were distributed at the corner points of the samples. The large dip angle samples were broken considerably, and multiple fracture zones were present. Under pressure, the filled cement slurry weakened the stress concentration, and bore the compressive stress and shear stress, and the interface friction with the sample prevented the cracking and expansion of the crack, which resulted in a reinforcement effect on the sample. Our findings might act as a reference for the filling engineering of rock slopes with en-echelon joints. Highlights: Studying the effect of grouting reinforcement on the mechanical strength of rocks and fracture behavior is of great significance in engineering applications. The findings of this study might contribute to the field of filling defects and provide information that may help engineers with the filling and strengthening of rock slopes. In this study, the effects of filling cement on fracture behavior and strength of gabbro at different prefabricated joint angles were studied through compression tests, and the fracture mechanism of samples during loading was analyzed based on acoustic emission technology. Finally, the action mechanism of filling cement is explained. The filling cement slurry has remarkable reinforcement effect. Under the action of pressure, the filling cement slurry weakens the stress concentration, withstands the compressive stress and shear stress, and the interface friction with the sample prevents the crack cracking and expansion, which has a strengthening effect on the sample. [ABSTRACT FROM AUTHOR]

The main aim of this investigation is to develop backfill concrete including coal gangue and metakaolin to reduce solid waste. For this purpose, a total of 30 concrete mixtures were designed by the inclusion of 0%, 25%, 50%, 75% and 100% coal gangue as coarse aggregates and 0%, 10% and 20% metakaolin as binder at 0.55 and 0.45 water to cement ratios. The compressive strength was tested after 3, 7 and 28 days for a total of 90 samples. Meanwhile, the influences of coal gangue and metakaolin on the elastic modulus, ultrasonic pulse velocity, rebound number and open porosity were explored. Then, the relationship between physical and mechanical properties was revealed by design code expressions and empirical models. Furthermore, an extreme learning machine was developed to predict compressive strength by concrete mixtures. The results show that the inclusion of coal gangue results in a poor performance in physical and mechanical properties of concrete. However, the drawbacks of concrete containing coal gangue can be compensated by metakaolin. The predicted results of design code expressions and empirical models are closed to the experiment results, with a 10% error. In addition, the findings reveal that the extreme learning machine offers significant potential to predict the compressive strength of concrete with high precision. [ABSTRACT FROM AUTHOR]

Back azimuth (BAz) information can be determined from combined measurements of rotations and translations at a single site. Such six degree‐of‐freedom (6‐DoF) measurements are reasonably stable in delivering similar information compared to a small‐scale array of three‐component seismometers. Here we investigate whether a 6‐DoF approach is applicable to tracking seismic sources. While common approaches determining the timing and location of energy sources generating seismic waves rely on the information of P‐waves, here we use S‐waves. We track back azimuths of directly arriving SH‐waves in the two‐dimensional case, P‐converted SV‐waves, direct SV‐ and direct SH‐waves in the three‐dimensional case. For data analysis, we compare a cross‐correlation approach using a grid‐search optimization algorithm with a polarization analysis method. We successfully recover the rupture path and rupture velocity with only one station, under the assumption of an approximately known fault location. Using more than one station, rupture imaging in space and time is possible without a priori assumptions. We discuss the effects of rupture directivity, supershear rupture velocity, source‐receiver geometry, wavefield interference, and noise. We verify our approach with the analysis of moving traffic noise sources using 6‐DoF observations. The collocated classic seismometer and newly built ring laser gyroscope ROMY near Munich, Germany, allow us to record high‐fidelity, broadband 6‐DoF (particle velocity and rotational rate) ground motions. We successfully track vehicles and estimate their speed while traveling along a nearby highway using the estimated BAz as a function of time of a single station observation. Key Points: We demonstrate concepts for seismic source tracking from combined point measurements of translational and rotational motionsWe show that S‐waves can be used for seismic source tracking due to the wavefield separation in rotational componentsWe discuss the effects of directivity, rupture speed, source‐receiver geometry, and present a real data example of tracking traffic sources [ABSTRACT FROM AUTHOR]

• The effect of high temperature on the fracture mechanical behavior of rocks is a critical topic of research in underground engineering. • In this study, the yellow sandstone sample with single-side straight-crack (SC3PB) was heat treated at 25–800 ℃, and the loading process of the sample was monitored by acoustic emission and DIC technology. • The results of the study can provide guidance for ensuring safety during geotechnical engineering construction and a theoretical basis for sandstone fracture behavior. • The physical and mechanical properties and fracture behavior of SC3PB yellow sandstone changed substantially at the threshold temperature of 400 ℃. The effect of high temperature on the fracture mechanical behavior of rocks is a critical topic of research in underground engineering. In this study, a single-side straight-crack three-point bending (SC3PB) yellow sandstone sample was heat treated at 25, 200, 400, 600, and 800 ℃. The fracture toughness of the sample was measured after heat treatment, and the deformation and failure process of yellow sandstone under load was monitored using acoustic emission and digital image correlation technology. The results revealed that the p-wave velocity, peak load and fracture toughness of yellow sandstone decreased considerably when temperature exceeded 400 ℃. By contrast, with the increase in temperature, the crack length and peak propagation rate increased considerably. Furthermore, with the increase in load, a high-strain band was observed in the the von-Mises strain in the loading direction. The fracture toughness was linearly correlated with the p-wave velocity, peak load and thermal damage. When temperature was higher than 400 ℃, the main fracture expanded and the plastic characteristics increased after the peak load. The rapid change in the physical and mechanical properties of 400-600℃ yellow sandstone was attributed to the α/β phase transition of quartz, the dehydroxylation of kaolinite and the escape of intermineral binding water and crystal water. Therefore, the physical and mechanical properties and fracture behavior of SC3PB yellow sandstone changed substantially at the threshold temperature of 400 ℃. [ABSTRACT FROM AUTHOR]

Generally, defects passivation and stability enhancement against humidity are two independent open questions in exploring high-performance perovskite solar cells. Here, a high-efficient and stable perovskite solar cell is fabricated by introducing dual-functional 2-Fluorothiophenol (FTP) as an anti-solvent additive. The FTP can not only greatly reduce the defects within perovskites, but also effectively improve the hydrophobicity of the perovskite films. [Display omitted] • Dual-functional FTP blended with CB is used as an antisolvent for the first time. • FTP incorporation induces the oriented crystallization and reduces the defects. • FTP boosts the efficiency from 16.86% to 20.01% for 1.0 cm2 devices. • The PSCs with FTP incorporation exhibit an outstanding humidity stability. Ionic defects and humidity instability are the main limitations to realize the commercialization of FA-based perovskite solar cells. To overcome these issues, here, we report a dual-functional molecular 2-Fluorothiophenol (FTP) to achieve high-quality FA-based perovskites with simultaneously efficient defects passivation and improved hydrophobicity. It is revealed that SH¯ groups of FTP induce highly oriented crystallization toward (0 0 1) crystal plane of cubic-phase Cs 0.05 FA 0.95 PbI 3 perovskite structure, thus improving the charge carrier transport. Moreover, a strong Lewis acid-base interaction between the SH¯ group and Pb2+ in perovskite is of great benefit to passivate the surface and grain boundary defects, with additional merit for improving humidity stability of the FA-based perovskite films in conjunction with the hydrophobic group of FTP. The introduction of FTP boosts the efficiency from 20.30% to 22.66% for 0.04 cm2 solar cells and from 16.86% to 20.01% for 1.0 cm2 devices. More importantly, the solar cells demonstrate excellent humidity stability, which can retain 90% of their original efficiency after being kept for 80 days under ambient air conditions. [ABSTRACT FROM AUTHOR]

The HC(NH2)2+(FA+) is a well‐known substitute to CH3NH3+(MA+) for its capability to extend light utilization for improved power conversion efficiency for perovskite solar cells; unfortunately, the dark cubic phase (α‐phase) can easily transition to the yellow orthorhombic phase (δ‐phase) at room temperature, an issue that prevents its commercial application. In this report, an inorganic material (NbF5) is developed to stabilize the desired α‐phase perovskite material by incorporating NbF5 additive into the perovskite films. It is found that the NbF5 additive effectively suppresses the formation of the yellow δ‐phase in the perovskite synthesis and aging process, thus enhancing the humidity and light‐soaking stability of the perovskite film. As a result, the perovskite solar cells with the NbF5 additive exhibit improved air stability by tenfold, retaining nearly 80% of their initial efficiency after aging in air for 50 d. In addition, under full‐sun AM 1.5 G illumination of a xenon lamp without any UV‐reduction, the perovskite solar cells with the NbF5 additive also show fivefold improved illumination stability than the control devices without NbF5. [ABSTRACT FROM AUTHOR]

Additional observations of rotational motions (i.e., six-components or 6C) records allow us to separate wave types (P- and S-waves), estimate propagation direction and phase velocities. One of the most important issues is the question about seismic anisotropy diagnostic of fracture characterization in reservoirs. The impact of anisotropy on rotational motions is entirely unexplored. The possible use of joint measurements of translational and rotational motions in borehole seismic is investigated by performing walkaround VSP simulations. The seismograms are synthesized using the spectral element method SALVUS software package (salvus.io). We simulate 6C synthetic VSP gathers for varying azimuths and investigate what anisotropic characteristics can be determined from co-processing of rotations and translations. The results indicate that it might be time to develop 6C borehole sensors of appropriate sensitivity for exploration applications. [ABSTRACT FROM AUTHOR]

With the availability of new instrumentation for complete ground motion measurements (e.g., rotation sensing, strain measurements) the question on potential applications in seismology arises. From single-site combined measurements of rotations and translations (6 degrees of freedom) backazimuth information can be determined. Such measurements are reasonably stable, indicating the potential of a single point measurement returning similar information as a small-scale array of classic 3C seismometers. The S-wave field emitted during the shear failure of earthquake ruptures is inherently linked to rotational ground motions. Here we investigate whether a 6 DoF approach is applicable for tracking a finite rupture in the P- and S-wave field. We analyse 2D and 3D synthetic cases of unilateral but complicated rupture propagation. The backazimuth of directly arriving SH-waves (in the 2D case) and converted SV-waves (in the 3D case) are tracked. We explore data analysis based on wave polarity. A new statistical approach for combining the backazimuth estimates of several stations is presented which shows a high resistance with respect to measurement outliers. We successfully recover the rupture path and the rupture velocity with only one station in 2D and 3D, presupposed the fault position is known approximately a priori. Using more than one station, spatial rupture tracking is possible without any a priori assumptions. It is possible to correctly determine relatively small variations in rupture speed, and rupture jumping across off-set fault segments. We discuss effects of rupture directivity, supershear propagation speeds, the geometry between source and receiver and shortcomings of the method. [ABSTRACT FROM AUTHOR]

With the recent installation of the high-sensitivity multicomponent ring laser ROMY at the Munich Geophysical Observatory for the first time 6-component (3C translations and 3C rotations) are available covering observations from ocean-generated noise, local, regional, and global earthquakes. In addition, the Wettzell G-ring laser (vertical component of rotation only), operational since 2002 some 200km away, provides the opportunity to compare observations and understand the impact of local geological setting on the joint observables. Here we discuss analysis of 6-C seismograms demonstrating the array-like processing style yet from single point measurements. This includes the estimation of phase velocity, backazimuth, phase separation, dispersion curves, local 1D velocity structure and others. We investigate the effect of local site conditions (bedrock at Wettzell and sedimentary rocks in Munich) on teleseismic wavefields. We also discuss the impact of 6C processing schemes on seismic exploration, earthquake physics, and planetary seismology. [ABSTRACT FROM AUTHOR]

Inorganic tin–lead perovskites with low bandgap (1.2–1.4 eV) are desired absorber materials for solar cells owing to their ideal bandgap and compositional stability. However, such tin–lead perovskites are currently subject to inferior power conversion efficiency (PCE) and the origin remains unclear. Here, for the first time, we report the metal-cation-derived unsynchronized crystallization behavior of inorganic tin–lead perovskite, exemplifying by a representative composition CsPb0.7Sn0.3I3. A tin-perovskite-targeted crystallization modulation agent, 1-(4-fluorophenyl) piperazine (1-4FP), is introduced to synchronize the B-site alloying through its strong targeted bonding with SnI2, resulting in substantially enhanced film quality with better morphology and photoelectrical properties. Furthermore, first-principles molecular dynamics simulations reveal that the agent regulates the crystallization route toward the pure phase of CsPb0.7Sn0.3I3 by suppressing the preforming of tin perovskite. With our proposed approach, the best device attains PCE of 17.55%, which is record-high for inorganic tin–lead perovskite solar cells. In addition, treated devices show excellent stability with only 10% and negligible loss after being exposed to 1 sun intensity for 700 h and being stored in N2 after over 4000 h, respectively. Our findings open a new avenue of crystallization route design in inorganic tin–lead perovskites, so as to obtaining high-quality perovskite films and associated solar cells. [ABSTRACT FROM AUTHOR]

The high speed development of industries such as new energy power, medical instruments, under¬ground exploration, and high power pulses are demanding more and more dielectric capacitors. Polymer based film capacitors are attracting attention for their high power density, high breakdown field strength, high reliability, low loss, and small size. However, the low energy density due to the low dielectric constant of the polymer itself has limited IS application n high-end fields. And polymer as an effective way to enhance the energy density by compounding with other organic or inorganic materials in different ways. This paper introduces the current research status of polymer based film capacitors compounded with inorganic materials, analyzes the advantages and shortcomings of different compounding methods, and discusses the future development prospects of polymer based film capacitors. [ABSTRACT FROM AUTHOR]

Limestone is a widely used natural building material, and its physical and mechanical properties can change greatly when exposed to high-temperature heat sources. In this paper, limestone samples from Linyi City, Shandong Province, were selected and some of them were heated to 650 °C at different heating rates (4, 6, and 8 °C min−1), while the rest of the samples were heated cyclically (200, 300, 400, 500, 600, and 650 °C) at a heating rate of 8 °C min−1, and the acoustic emission (AE) signals were recorded throughout. The results show that the AE signal rate increases with increases in temperature, and the AE signal increases rapidly at 300 °C and 500 °C because of the thermal decomposition of dolomite and calcite. There is a negative correlation between the heating rate and the AE signal rate. The high-frequency data and high-amplitude data generated by AE are negatively correlated with the heating rate. With the increase in the heating rate, AE counts and cumulative AE counts decrease significantly. [ABSTRACT FROM AUTHOR]

• The variations in mode I fracture toughness of gabbro after a high-temperature thermal fatigue treatment were studied. • The temperature and the number of cycles affected the fracture toughness of the gabbro. • Cracks mainly developed at the loading points and the prefabricated crack of the rock specimen. • The high-temperature phase transformations of plagioclase and pyroxene changed the rock structurally. Investigating variations of rock fracture toughness after high-temperature thermal fatigue is greatly significant for developing deep geothermal resources. This study investigated the mode I fracture toughness of gabbro after high-temperature fatigue treatment by heating a cracked straight-through Brazilian disc (CSTBD) gabbro specimen to 200, 400, 500, and 600 °C, followed by 100 thermal cycles. Additionally, acoustic emission (AE) and digital image correlation (DIC) were used to monitor the failure process of gabbro. The results showed that the peak load, fracture toughness, and fracture energy of gabbro decreased with the increased temperature and number of cycles, which was most significant at 500 and 600 °C. Under mode I loading, cracks developed along the loading direction and connected with the prefabricated crack. Additionally, the regions with higher von Mises equivalent strain (Evm) values were concentrated at the loading points and prefabricated crack of the rock sample. The degree of bending of the primary cracks increased, the number of secondary cracks increased, and the Evm values changed significantly as the temperature increased. The phase transformation of plagioclase feldspar at 450 °C and the oxidation of iron- and magnesium-containing pyroxene at 600 °C changed the internal structure of the rock. Cyclic treatment further exacerbated the thermal damage, developing microcracks within the rock and reducing fracture toughness significantly. [ABSTRACT FROM AUTHOR]

Single-component ring lasers have provided high-resolution observations of Earth's rotation rate as well as local earthquake- or otherwise-induced rotational ground motions. Here, we present the design, construction and operational aspects of ROMY, a four-component, tetrahedral-shaped ring laser installed at the Geophysical Observatory Fürstenfeldbruck near Munich, Germany. Four equilateral, triangular-shaped ring lasers with 12 m side length provide rotational motions that can be combined to construct the complete vector of Earth's rotation from a point measurement with very high resolution. Combined with a classic broad-band seismometer, we obtain the most accurate 6 degree-of-freedom ground motion measurement system to date, enabling local and teleseismic observations as well as the analysis of ocean-generated Love and Rayleigh waves. The specific design and construction details are discussed as are the resulting consequences for permanent observations. We present seismic observations of local, regional and global earthquakes as well as seasonal variations of ocean-generated rotation noise. The current resolution of polar motion is discussed and strategies how to further improve long-term stability of the multicomponent ring laser system are presented. [ABSTRACT FROM AUTHOR]

• Combined 1-4FP additive and post-treatment strategy was adopted in tin–lead PSCs. • High-quality perovskite film was obtained via significant surface reconstruction. • Crosslinking neighboring perovskite grains with N-H bonds prevented tin oxidation. • Target PSC delivered a PCE of 17.19 % with a record small Voc deficit of 0.426 V. • 17.19% is the highest efficiency among all-inorganic Pb-Sn PSCs reported to date. Inorganic CsPb 0.7 Sn 0.3 I 3 perovskites with low-bandgap (1.2 to 1.4 eV) are desired absorber materials for solar cells owing to their ideal bandgap and compositional stability. However, the performances of inorganic Pb-Sn perovskite solar cells are much lower than their Pb-based and hybrid Pb-Sn (e.g. CsPbX 3 and FAMAPbSnX 3) PSCs, which might be ascribed to its poor film-forming morphology and easy oxidation of Sn2+ at the surface. Here, for the first time, a combined 1-(4-fluorophenyl) piperazine (1-4FP) additive and 1-4FP post-treatment strategy was adopted to obtain high-quality pinhole-free films through a significant surface reconstruction. Specifically, the interaction introduced by 1-4FP post-treatment can effectively prevent the inevitable Sn2+ oxidation on perovskite surface, resulting from crosslinking neighboring perovskite grains with hydrogen bonds of amine group binding to the perovskite surface. As a result, the device treated by this combined strategy achieved a PCE of 17.19 %, which is the highest efficiency of Pb-Sn alloyed inorganic PSCs (sub-1.4 eV) reported to date. In addition, the unsealed 1-4FP-treated devices maintained their initial efficiencies of approximately 100 % after storage in a nitrogen atmosphere for 4000 h. Our findings open a new avenue to obtain high-quality inorganic Pb-Sn perovskite films and associated solar cells. [ABSTRACT FROM AUTHOR]

Recent progress in rotational sensor technology has made it possible to directly measure rotational ground-motion induced by seismic waves. When combined with conventional inertial seismometer recordings, the new sensors allow one to locally observe six degrees of freedom (6DOF) of ground-motion, composed of three orthogonal components of translational motion and three orthogonal components of rotational motion. The applications of such 6DOF measurements are manifold—ranging from wavefield characterization, separation, and reconstruction to the reduction of non-uniqueness in seismic inverse problems—and have the potential to revolutionize the way seismic data are acquired and processed. However, the seismological community has yet to embrace rotational ground-motion as a new observable. The aim of this paper is to give a high-level introduction into the field of 6DOF seismology using illustrative examples and to summarize recent progress made in this relatively young field. It is intended for readers with a general background in seismology. In order to illustrate the seismological value of rotational ground-motion data, we provide the first-ever 6DOF processing example of a teleseismic earthquake recorded on a multicomponent ring laser observatory and demonstrate how wave parameters (phase velocity, propagation direction, and ellipticity angle) and wave types of multiple phases can be automatically estimated using single-station 6DOF processing tools. Python codes to reproduce this processing example are provided in an accompanying Jupyter notebook. [ABSTRACT FROM AUTHOR]

The defect passivation in the bulk of metal oxide electron transport layers and at the electron transport layers/perovskite interfaces is one of the pivotal roles that enhance electron injection and extraction to gain the high-performing planar perovskite solar cells. Herein, we incorporate the sodium chloride dopants into the compact TiO 2 as electron transport layers at a low temperature of 200 °C. It is demonstrated that the appropriate sodium chloride additive can effectively passivate the bulk and surface defects of the intrinsic TiO 2 , suppressing oxygen vacancies-induced nonradiative recombination centers and improving electron extraction and collection. Simultaneously, the proper sodium chloride treatment remarkably enhances the TiO 2 conductivity, reduces the water contact angle, and further indirectly optimizes the morphology of perovskite layer. With 5.0 mol% sodium chloride-incorporated TiO 2 , the perovskite solar cells exhibit the enhancement in the photovoltaic parameters because of the lower carrier recombination and faster charge transport, contributing to efficiency up to 19.84% with small hysteresis. More importantly, this sodium chloride-modified electron transport layer based perovskite solar cell also emerge a considerable long-term air-storage stability of about 80% of its initial efficiency after 800 h. Image 1 • NaCl additive effectively passivates defects in the bulk and surface of TiO2 film. • Perovskite layer fabricated on 5% NaCl-doped substrate presents large grain growth. • The device with 5% NaCl-doped ETL yields the PCE of 19.84% with small hysteresis. • The PSC with 5% NaCl-doped ETL shows great long-term air-storage stability. [ABSTRACT FROM AUTHOR]

The Cs‐based inorganic perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with power conversion efficiency (PCE) over 16% and potential to be used as top cells for tandem devices. Herein, I− is partially replaced with the acetate anion (Ac−) in the CsPbI2Br framework, producing multiple benefits. The Ac− doping can change the morphology, electronic properties, and band structure of the host CsPbI2Br film. The obtained CsPbI2−xBr(Ac)x perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI2Br films. Interestingly, the CsPbI2−xBr(Ac)x PSCs exhibit a maximum PCE of 15.56% and an ultrahigh open circuit voltage (Voc) of 1.30 V without sacrificing photocurrent. Notably, such a remarkable Voc is among the highest values of the previously reported CsPbI2Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI2−xBr(Ac)x PSCs exhibit high reproducibility and good stability. The stable CsPbI2−xBr(Ac)x PSCs with high Voc and PCE are desirable for tandem solar cell applications. [ABSTRACT FROM AUTHOR]

Hole transport layers (HTLs) plays critical role in CsPbI 2 Br perovskite solar cells (PSCs). However, few studies have been done to develop new and sensitive-dopant-free HTL for CsPbI 2 Br PSCs. Here, a low-cost fluorinated N',N',N'',N''-tetrakis(4-methoxyphenyl)spiro[fluorene-9,9'-xanthene]-2,7-diamine (2mF-X59) was synthesized and applied as sensitive-dopant-free HTL into CsPbI 2 Br PSCs. After modified the 2mF-X59 and CsPbI 2 Br surface by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquino-dimethane (F4-TCNQ), a maximum power conversion efficiency (PCE) of 14.42% was obtained for CsPbI 2 Br PSC with an impressive open-circuit voltage (V oc) of 1.23 V, which is higher than that of the most previously reported CsPbI 2 Br PSCs with the doped Spiro-OMeTAD. More importantly, the CsPbI 2 Br PSCs with the newly developed HTLs showed remarkable stability retaining more than 94% of their initial PCE value after aging in air for 30 days without encapsulation. Therefore, we firmly believe that our new 2mF-X59 HTL created via molecular engineering is a promising candidate for preparing high performance CsPbI 2 Br PSCs. A new sensitive-dopant-free HTL (2mF-X59) was synthesized and successfully applied in a planar CsPbI 2 Br PSC. A power conversion efficiency (PCE) of 14.42% was obtained in the CsPbI 2 Br PSC with 2mF-X59 + F4-TCNQ as HTL by interface engineering. The unencapsulated device displayed remarkable stability, retaining above 94% of its initial PCE after storing in ambient atmosphere for 30 days. Image 1 • 2mF-X59 was firstly synthesized to instead of spiro-OMeTAD in CsPbI 2 Br perovskite solar cells. As we know, few works have been report about using new HTL in inorganic perovskite solar cell. • F4-TCNQ was used as additive for 2mF-X59 hole transport layer (HTL), A High efficiency of 13.42% was obtained in CsPbI 2 Br solar cell with 2mF-X59 + F4TCNQ HTL, which is comparable to device with spiro-OMeTAD + Li-TFSI + t-BP as HTL (PCE = 13.75%). • In order to further improve the efficiency of CsPbI 2 Br solar cell, F4-TCNQ was used to passivate the surface of CsPbI 2 Br film. The efficiency of CsPbI 2 Br solar cell with 2mF-X59 + F4TCNQ HTL was further improved from 13.42 to 14.42%. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead halide perovskite solar cells (PSCs), such as CsPbI2Br, have made a striking breakthrough with a power conversion efficiency of over 16%. However, CsPbI2Br is known to be very sensitive to moisture, and the intrinsic long‐term stability of CsPbI2Br film remains a critical challenge. Interface engineering has been proven to be an effective way for solving the instability‐to‐moisture issue and enhancing the performance of inorganic–organic hybrid PSCs, while there are a few reports on interface engineering for inorganic PSCs. Here, a conjugated polymer, poly(N‐alkyldiketopyrrolo‐pyrrole dithienylthieno[3,2‐b]thio‐phene) (DPP‐DTT), with high mobility is introduced as a novel interface passivation for CsPbI2Br PSCs, which can significantly reduce nonradiative recombination in perovskite, leading to significant enhancement in both efficiency and stability of CsPbI2Br PSCs. Through DPP‐DTT passivation, a champion efficiency of 15.14% is obtained in CsPbI2Br PSCs. Moreover, the Lewis base DPP‐DTT can serve as an ultrahydrophobic agent to hold the photovoltaic performance of CsPbI2Br PSCs under ambient environment with humidity or thermal stress. These results provide a simple while highly effective route of fabricating the highly efficient and stable inorganic PSCs. [ABSTRACT FROM AUTHOR]