Humidity Stability Research Articles

F-doping-Enhanced Carrier Transport in the SnO2/Perovskite Interface for High-Performance Perovskite Solar Cells.

SnO2 is widely used as the electron transport layer (ETL) in n-i-p perovskite solar cells. However, the deep-level defects at the interface between SnO2 and the perovskite film will lead to energy loss, reducing the open-circuit voltage. Therefore, the interface optimization is essential to raise the efficiency and enhance the stability of perovskite solar cells. In this work, we introduce NH4F into the SnO2 electron transport layers, and the optimized SnO2 films reduce the interface defect density, improve the charge extraction, and reveal a better energy-level arrangement. Compared to the conventional SnO2 perovskite solar cell, the average Voc is improved by 70 mV with the champion efficiency up to 22.12%. Moreover, the unencapsulated F-doped SnO2 perovskite solar cells show better thermal stability (maintained 86.2%) and humidity stability (maintained 80.8%) after 35 days.

Scalable spray coated high performance sulfurized electron transporter for efficient and stable perovskite solar modules

The stability issue has been acknowledged as the bottleneck in the practical application of perovskite photovoltaics, while the stabilized interface between the perovskites and charge transport layers dominates their stability performance under different stresses. Here, we developed a high-performance sulfurized zinc-titanium mixed oxide (ZTO-S) electron transport layer (ETL) to fabricate large-area efficient and long-term 85 °C/85% RH stable perovskite solar modules. The scalably prepared ZTO-S using the facile spray coating method demonstrates excellent electron mobility close to that of ZnO, in addition to promoting the uniform crystallization of perovskite film across the entire module via the interaction between surface S and Pb2+. Furthermore, this novel coordination stabilized the interface and reduced the interfacial non-radiative recombination defects within the devices, yielding an efficient and stable performance for the modules. High efficiency of 21.73% and 17.50% was achieved for blade-coated 36 cm2 and 100 cm2 perovskite solar modules, respectively. In addition, the encapsulated module (36 cm2) shows an attractive humidity and heat stability (85 °C/85% RH) performance with a maintained 93.5% of the initial PCE over 1000 h.

Inducing crystal-oriented growth while inhibiting grain boundary migration with multifunctional ionic liquid for high-efficiency perovskite solar cells

The uncoordinated Pb2+ and X- vacancy defects caused by the uncontrollable crystallization process are detrimental to the efficiency and stability of perovskite solar cells (PSCs). Herein, a multifunctional ionic liquid 1-butyl-3-methylimidazolium hexafluoroan (BMIMSbF6) is introduced into perovskite to form an intermediate phase to induce crystal-oriented growth and passivate intrinsic defects. The results demonstrate that PbI2·BMIMSbF6 intermediate phase can delay the crystallization rate through molecular exchange and induce the crystal-oriented growth of perovskites. Moreover, by passivating uncoordinated Pb2+ and X- vacancy defects, BMIMSbF6 promotes the grain coarsening of perovskite and inhibits the grain boundary migration with an Urbach energy decreased by 10 meV. As a result, the PSCs with the BMIMSbF6 additive achieves a champion power conversion efficiency (PCE) of 22.03% and improved long-term stability. In addition to comprehensively controlling the growth of perovskite, the chemically stable BMIMSbF6 could prevent water infiltration to protect the perovskite and enhance its humidity stability. Thus, the PSCs with BMIMSbF6 additive maintains 85% of its initial PCE after aging at 45% relative humidity for 500 h. This work highlights the multifunctional roles of BMIMSbF6 to induce crystal-oriented growth, passivate intrinsic defects, and enhance humidity stability to form efficient and stable PSCs.

Polyelectrolyte/Graphene Oxide Nano-Film Integrated Fiber-Optic Sensors for High-Sensitive and Rapid-Response Humidity Measurement.

Optical fiber humidity sensors have sparked enormous interests in many fields because of their excellent features. However, it remains a great challenge to balance sensitivity, humidity response, temperature crosstalk, and wet hysteresis for real-world application. To overcome this trade-off, an optical fiber humidity sensor is developed here by coating functional graphene oxide (GO)/polyelectrolyte nanocomposite film on the excessively tilted fiber grating (ex-TFG), in which GO/polyelectrolyte nanocomposite film is employed for enhancing the hydrophilicity and accelerating the adsorption/desorption of water molecule, while the ex-TFG is utilized for improving the sensitivity of refractive index and eliminating the crosstalk of temperature. By this design, optical fiber humidity sensors achieve high sensitivity, rapid response and recovery, low hysteresis, and temperature crosstalk as well as excellent repeatability and stability in large relative humidity (RH) range. Our work provides a promising platform for effective RH monitoring systems that can be widely applied in rapid diagnostics, pharmacy, precision medicine, and so forth.

Construction of hydrogel composites with superior proton conduction and flexibility using a new POM-based inorganic–organic hybrid

Polyoxometalates (POMs) have attracted extensive interests as solid-state proton conductors due to their high conductivity and good thermal stability. However, the low humidity stability and poor mechanical property of crystalline POMs greatly hinder their practical application. Herein, on the basis of the remarkable improvement of the humidity stability that can be achieved by hybridizing POMs with organic components, we prepared a new POM-based inorganic–organic hybrid, H[Zn(Hapca)₃][PW₁₂O₄₀]·7H₂O <strong>1</strong> (Hapca = 3-aminopyrazine-2-carboxylic acid), composed of Keggin-type PW₁₂O₄₀³⁻ anions and Zn(Hapca)₃²⁺ cations. Compound <strong>1</strong> exhibits a proton conductivity of 1.16 × 10⁻⁴ S·cm⁻¹ at 55 °C, which remains stable at a relative humidity of 95%. To construct POM-based conductive materials with good mechanical property, we introduced <strong>1</strong> into a poly(vinyl alcohol) (PVA)/glycerol (Gly) hydrogel and obtained the hydrogel composites <strong>1@PVA/Gly-</strong><i><strong>x</strong></i> (<i>x</i> = 20%, 30%, and 40%, where <i>x</i> is the percentage of the mass of <strong>1</strong> to the total mass of <strong>1</strong> and PVA<strong></strong>). Remarkably, the hydrogel composites <strong>1@PVA/Gly-</strong><i><strong>x</strong></i> combine the merits of their components. The proton conductivity of <strong>1@PVA/Gly-40%</strong> reaches 1.11 × 10⁻² S·cm⁻¹ at ambient humidity and 75 °C, outperforming most POM-based composite materials reported to date. Moreover, <strong>1@PVA/Gly-40%</strong> displays good elasticity and toughness and high strain sensitivity. Additionally, we assembled <strong>1@PVA/Gly-40%</strong> into a strain sensor for the effective monitoring of various human activities. This work provides a new platform for the transformation of crystalline POM-based inorganic–organic hybrids into materials with good mechanical properties.

High efficiency stable planar perovskite solar cells via heavy water additive

Although great advances have been made in low-cost manufacturing of air-processed perovskite solar cells (PSCs), the moisture degradation of halide perovskite films remains a key problem to be urgently solved. High-quality perovskite films with large grains and uniform coverage are essential to enhance the performance of PSCs with high efficiency and moisture stability. Herein, heavy water (D2O) is employed as an additive in PbI2 precursor to manipulate the average grain size and enhance surface coverage of perovskite film, resulting in improved humidity stability of PSCs under ambient conditions. It is found that the introduction of D2O effectively improves the quality of perovskite film and significantly reduces the grain boundaries for reduced carrier recombination. The optimal concentration of D2O can boost the in-plane growth of perovskite films and increase the average grain size of perovskite from 494 nm to 717 nm. Consequently, the PSCs based on the perovskite film with 1% D2O exhibits a superior PCE of 21.66% (0.055 cm2) in small area, which is 9.78% higher than that of the control device (19.73%). In addition, the large-area (1 cm2) PSCs with 1% D2O show an efficiency of 20.02%. The unencapsulated PSCs made with 1% D2O can remain 95% of its initial PCE after aging 60 days in ambient air under dark with 20–25% relative humidity.

Bromide Incorporation Enhances Vertical Orientation of Triple Organic Cation Tin‐Halide Perovskites for High‐Performance Lead‐Free Solar Cells

Tin‐halide perovskite solar cells (THPSCs) are attractive in the photovoltaic field as promising candidates to address the issue of potential lead toxicity and approach the theoretical efficiency limit in lead‐halide perovskite photovoltaics. Nevertheless, THPSCs suffer from fast crystallization, low defect tolerance, mismatched energy levels, as well as severe oxidation from Sn2+ to Sn4+, leading to the low performance of devices. Herein, bromide is incorporated in the PEA0.15EA0.15FA0.70SnI1−XBrX perovskite precursor, which produces 2D/3D hybrid cations tin‐halide perovskite films with highly vertical oriented crystallization, favorable band‐level alignment, and suppressed tin oxidation. This leads to the decrease of trap density and charge recombination losses and the enhancement of charge carrier extraction in THPSCs. Consequently, the power conversion efficiency of the optimal THPSC (X = 0.30) surges to 10.12% in contrast to 7.13% of the control device (X = 0.00), along with a nearly eliminated current–voltage hysteresis. Furthermore, bromine‐incorporated THPSCs exhibit outstanding light soaking and humidity stability. These results are also in good agreement with the density functional theory calculations. This compositional engineering with Br could become a promising approach for improving the efficiency and stability of THPSCs.

Facile preparation of humidity stable green γ‐cyclodextrin metal–organic framework monolith for CO2 capture

AbstractProcessing powdered metal–organic frameworks (MOFs) into more usable forms can greatly expand their practical applications. We report a very simple and efficient method for synthesizing a green‐friendly γ‐cyclodextrin (CD)‐MOF monolith (rather than powder), without using any connectors or high temperature/pressure. Compared with the γ‐CD‐MOF‐powder, the γ‐CD‐MOF‐monolith showed much better humidity stability because the MOF particles in the γ‐CD‐MOF‐monolith were tightly packed. In addition, the CO2 adsorption test indicated that it had a higher volume adsorption capacity for CO2, with adsorption capacities of 44.04 and 36.85 cm3/cm3 at 0 and 25°C, respectively. The γ‐CD‐MOF‐monolith can maintain its porous structure and gas adsorption capacity even after 14 days of exposure to humid conditions, and the amount of CO2 absorption remains almost unchanged. This humidity stable γ‐CD‐MOF‐monolith is expected to have greater practical applications than its powdered counterpart in many applications including CO2 adsorption.

A full range of defect passivation strategy targeting efficient and stable planar perovskite solar cells

Defects and inferior charge transport dynamics within devices are key issues that inhibit the improvements of photovoltaic performance and stability. Developing facile and feasible strategies for synchronous passivation of defects regarding charge transport layers (CTLs), perovskite films and their interfaces, and precise tuning of energy level structure, is a definite way to solve above problems. Herein, we develop a synergistic passivation strategy for perovskite films and bilateral interfaces to improve device performance. Firstly, an appropriate amount of phenylethylammonium chloride is adopted to modify SnO2 electron transport layer (ETL). The complexation reaction between N atoms in –NH2 and Sn4+ improve the agglomeration of SnO2 nanoparticles and film quality of SnO2 ETL. The presence of Cl− ions not only effectively fill oxygen vacancies within SnO2 ETL, but also participate in regulating crystal growth dynamics of perovskite films, thus improving electron transport properties at interface. Subsequently, p-type conducting material N,N'-Bis-(1-naphthalenyl)-N,N'-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) is introduced into anti-solvent chlorobenzene during the preparation of perovskite films to further regulate the crystal quality and achieve full-range defect passivation. Particularly, the introduction of NPB helps to construct a gradient heterojunction between upper perovskite film and SpiroOMeTAD hole transport layer, thus reducing the accumulation of hole carriers near interface and further suppressing current–voltage hysteresis behavior of devices. Additionally, the hydrophobicity of NPB and full range of defect passivation greatly enhance the humidity and thermal stability of devices. Finally, a high power conversion efficiency of 21.88% is obtained with suppressed hysteresis and enhanced long-term stability. This work highlights the role of full-range defect passivation on CTLs, perovskite absorption layers and interfacial charge transport properties, which provide a novel concept for constructing high-performance and stable perovskite devices.

Effect of Humidity on the Thermal Properties of Aluminum Nanopowders with Different Surface Coatings

To investigate the effect of surface coating materials on the humidity stability of aluminum (Al) nanopowders, three kinds of core–shell structure Al nanopowders with an Al2O3 passivation coating, carbon coating, and plasticizer dioctyl sebacate (DOS) coating were prepared through laser-induction complex heating method. After one year’s storage at 95% relative humidity, their thermal properties were tested through differential scanning calorimeter (DSC) and thermal gravimeter (TG) analysis. The results show that the thermal properties of Al2O3-passivated Al nanopowders are entirely lost under high humidity because the Al2O3 passivation coating is very sensitive to moisture. The thermal properties of carbon-coated Al nanopowders are not well-protected under a high humidity due to the uneven thickness and structural defects of carbon coatings. However, the thermal enthalpy of DOS-coated Al nanopowders remains at 3.56 KJ/g under high humidity, which indicates that an organic DOS coating with a hydrophobic nature has an excellent protective effect on the thermal properties of the Al nanopowders. Given the good forming performance of organic DOS coatings and other components of propellants, DOS-coated Al nanopowders are a kind of energetic material with potential application value.

Simultaneous interface passivation and defect compensation for high-efficiency planar perovskite solar cells

Interfacial defects at the electron transport layer (ETL) and perovskite interface significantly impact the interface carrier dynamics and thus the performance of planar perovskite solar cells. Here, a synergistic strategy has been proposed to compensate for oxygen vacancies and halogen vacancies at the ETL/perovskite interface by constructing a Na2S interface layer. The results show that the S atoms simultaneously bond with the Sn atoms in SnO2 and occupy the halogen vacancies in the perovskite and form a Pb-S-Sn conductive channel, which accelerates carrier extraction at the interface. In addition, the Na2S interface layer affects the growth of the perovskite film and passivates the grain boundaries, resulting in reduced defect density and increased grain size. Correspondingly, the target device achieves a significantly improved efficiency (21.2 %) compared to the pristine device (17.2 %) and maintains over 86 % of the initial efficiency after aging in the air for 1000 h with 35 % RH; while exhibiting improved humidity and thermal stability. The interface defect compensation strategy reported herein provides a simple and effective method for interface optimization to further improve device performance.

Humidity-Independent, Highly Sensitive and Selective NO2 Sensor Based on In2O3 Nanoflowers Decorated With Graphite Nanoflakes

Metal oxide semiconductor (MOS) gas sensor is an effective tool for NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> detection. However, their performance is seriously influenced by humidity due to water vapor poisoning, and it remains a challenge to develop an anti-humidity NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> MOS sensor. In this work, a humidity-independent, highly sensitive and selective NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sensor based on In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanoflowers decorated with graphite nanoflakes was fabricated, which exhibited excellent anti-humidity and stability (response fluctuation within 7%) in a wide relative humidity (RH) range of 20% - 90%. The fabricated sensor had a high response of 10 to ppb level NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (RH 80%). Besides, the sensor exhibited good selectivity, low operating temperature (75 °C) and rapid response speed (50 s to 5 ppm NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The reason for the excellent anti-humidity function was investigated. Large amounts of polar groups were formed on the graphite nanoflakes after hydrothermal treatment, which enhanced the interaction between the graphite and In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and made the surface of the composites have a strong water absorption function. Moreover, the intrinsic hydrophobic property of the graphite can effectively block the interference of water vapor to the moisture-sensitive In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . Our work provides a new idea for enhancing the anti-humidity performance of the MOS sensors and can broaden their applications in a variety of complex environments.

Mixed potential type sensor based on Gd2Zr2O7 solid electrolyte and BiVO4 sensing electrode for effective detection of triethylamine

Triethylamine (TEA), as a common and widely used industrial raw material, is extremely hazardous to the environment and human health. Therefore, the development of a portable gas-sensing technology for high-efficiency detection of TEA is of great worth for human health and environmental monitoring. In this work, a mixed potential type TEA sensor was initially developed based on pyrochlore Gd2Zr2O7 solid state electrolyte and BiVO4 sensing electrode. The sensor generates high response values of − 62.2 mV and − 134.4 mV to 5 ppm and 100 ppm TEA at 500 °C, respectively. The response value of the sensor displays a logarithmic linear relationship with the concentration of TEA in the range of 1–100 ppm with the sensitivity of − 50.8 mV/decade. Besides, the sensor shows good response and recovery characteristics, and the response and recovery time to 10 ppm TEA is 10 s and 89 s, respectively. Moreover, the sensor possesses good humidity resistance, reproducibility and stability. The sensing behavior of the sensor is explained by the mixed potential sensing mechanism, which is confirmed by the measurement of the polarization curves. This work provides a good supplement for TEA gas sensor, which holds important application value for the sensitive detection of TEA in the environment.

Customizing a Coordinative Crab Molecule BCP‐3N with Multifunctionality for High‐Performance Inverted Perovskite Solar Cells

Defects at the perovskite grain boundaries and the interfaces between perovskite and charge transport layers in perovskite solar cells (PSCs) are a curse of nonradiative recombination losses and device degradation channels. Herein, the custom design and synthesis of a multifunctional small molecule (N 2,N 9‐bis(3‐(dimethylamino)propyl)‐4,7‐diphenyl‐1,10‐phenanthroline‐2,9‐dicarboxamide (BCP‐3N) featured by the π‐conjugated phenanthroline and an array of lone‐pair electron donor atoms from the carbonyl and amine groups are reported. The BCP‐3N is used as a Lewis base to multidentate passivate the undercoordinated Pb2+ ions forming an ultrathin tunnel layer, in synergy with ethanol as a green antisolvent to simultaneously orient the growth of perovskite, resulting in a significantly reduced defect density in perovskite films. With BCP‐3N, a significant increase in open‐circuit voltage (V oc = 1.12 V) is achieved of inverted (p–i–n structure) PSCs, along with a record power conversion efficiency of ≈21% among alcohol antisolvent processed cells. Also, attested are a much higher illumination and humidity stability of the BCP‐3N‐based device. Combined experimental and theoretical studies have uncovered the multifunctional roles of BCP‐3N in stabilizing high‐quality Cs–FA–MA triple‐cation mixed perovskites under light, bias, and humidity stresses, enlightening the molecular design for PSCs.

Synergetic Regulation of Oriented Crystallization and Interfacial Passivation Enables 19.1% Efficient Wide‐Bandgap Perovskite Solar Cells

AbstractWide‐bandgap (WBG) perovskite solar cells (PSCs) suffer from severe voltage loss, which significantly limits the enhancement of photovoltaic performance. Here, 4‐fluoro‐phenylethylammonium iodide (FPEAI) is used as a dual‐functional agent for oriented crystallization and comprehensive passivation of WBG PSCs. The additive of FPEAI promotes crystals to grow along with the (100) orientation with improved crystallinity and to spontaneously form Ruddlesden–Popper 2D perovskite on the grain boundary and surface of 3D crystals, which can passivate defects and protect the perovskite film from moisture erosion as well as suppressed ion migration. In addition, the 2D/3D heterostructure induces a matched energy‐level alignment, which mitigates the detrimental interfacial charge recombination at the interface of the 3D perovskite and hole transport layer. Consequently, the modified WBG PSCs exhibit an improved open‐circuit voltage to 1.3 V and a fill factor of 77.8%, leading to a remarkable power conversion efficiency of 19.1% with negligible hysteresis. Furthermore, the WBG PSCs maintain 85% of the original efficiency after 1000 h in air, demonstrating outstanding humidity stability. This work indicates that FPEAI can be used as a dual‐functional agent to significantly enhance the efficiency of WBG PSCs.

High‐Resolution Patterning of 2D Perovskite Films through Femtosecond Laser Direct Writing

Abstract2D perovskites have been considered as promising candidates for optoelectronic devices due to their good optical and electronic properties compared to 3D perovskites with significantly higher stability. Considering the commercial applications involving displays, image sensors, and fluorescent anti‐counterfeiting labels, the patterning technique of 2D perovskites is urgently required. However, existing patterning approaches still have challenges in high‐resolution fabrication. Here, a facile femtosecond laser direct writing method to fabricate arbitrarily patterned 2D perovskite films with well‐defined profiles and uniform fluorescence properties is developed. The flexible, fine, and non‐thermal diffused patterning abilities of femtosecond laser facilitate diverse 2D perovskite patterns exhibiting bright emission without any pinholes and cracks, as well as high resolution of approximate 2 µm line width. Based on this efficient patterning technique, this study demonstrates fluorescent anti‐counterfeiting labels (quick response code embedded with microlines) based on 2D perovskite films with high humidity stability, which can be identified from 43% to 96% relative humidity. This high‐resolution, reliable, efficient, and facile patterning technique for 2D perovskites with high humidity stability provides a promising technical route for 2D perovskite‐based optoelectronic applications.

From Hazardous Waste to Green Applications: Selective Surface Functionalization of Waste Cigarette Filters for High-Performance Robust Triboelectric Nanogenerators and CO2 Adsorbents.

This article reports a novel and rational approach to convert waste cigarette filters (CFs), one of the largest sources of ocean pollution, into high-performance triboelectric nanogenerators (TENGs) and efficient CO2-capturing adsorbents. CFs are plasticized cellulose acetate, which take several years to degrade. To revalorize these fibers, selective amine surface functionalization is performed (10PAL-20T-CFs). For the proof of concept, when the modified fibers are employed in a TENG, it could generate an output voltage (96.63 V) and current (9.37 μA) that are, respectively, 43 and 8 times higher than those obtained employing the pristine CFs for the nanogenerator. The proposed TENG displays an instantaneous peak power of 3.75 mW, which is higher than that of many recently reported TENGs made from cellulose materials. Moreover, the TENG displayed outstanding durability to humidity and high-performance stability when it is subjected to cyclic loading (i.e., 12,000 cycles of loading-unloading). A 9 cm2 TENG could effectively light up 100 or more colored light-emitting diodes when it is manually pressed. Finally, the modified filter fibers show an excellent CO2 adsorption capacity of 1.93 mmol/g, which is 9.2 times higher than that obtained using the pristine fibers. These results demonstrate that hazardous wastes such as CFs can be upcycled into valuable resources.

α-Phase intermediate for efficient and stable narrow bandgap triple cation perovskite solar cells

Lead halide perovskite solar cells (PSCs) have attracted intensive attention since their power conversion efficiency (PCE) increased sharply in recent years. Thereinto, triple cation perovskite (TCP) is a popular light absorption layer for PSCs due to its excellent thermal and humidity stability. However, a large amount of MA+ (≥15%) and Br- (≥15%) in TCP makes the bandgap widen drifting from the optimum value. There is some extent of a trade-off between PCE and stability for PSCs, and narrow-bandgap TCP is one of the best choices for light absorption material to achieve an optimum balance between PCE and stability. Herein, we prepared a narrow-bandgap (1.56 eV) high-quality TCP (Cs0.05FA0.86MA0.09Pb(I0.97Br0.03)3) film with an average grain size up to 1208 nm and corresponding PSC with high efficiency of 20.8%. Moreover, the intermediate process of the TCP film crystallization was carefully studied disclosing the critical α-Phase intermediate and corresponding roles of DMSO solvent and MACl additive through quasi-in-situ XRD in the film formation process, and the results may give critical clues to the fabrication of high-quality narrow-bandgap TCP based PSCs.

An excitation wavelength-dependent color-tunable La4GeO8: Bi3+, Er3+ phosphor for multicolor anticounterfeiting

Stimulation-responsive luminescent materials have attractd intense attention due to their excellent optical properties in the anticounterfeiting application. At present, most the anticounterfeiting materials are based on single luminescence and fixed excitation patterns, resulting in a poor anticounterfeiting effect. Therefore, developing multimodal anticounterfeiting materials that change their luminous color under different wavelength stimuli has become a significant challenge. In this work, we reported a multimodal luminescent La 4 GeO 8 : Bi 3+ , Er 3+ phosphor, which could emit white, blue-green, baby blue and orange-yellow light at the excitation wavelength of 250–430 nm. Moreover, it also showed green upconversion (UC) luminescence when irradiated with near-infrared (NIR, 980 nm and 808 nm) lasers. Notably, the material exhibited good humidity resistance and stability. Based on these integrated features, we designed an anticounterfeiting device. The results suggested that the anticounterfeiting device could quickly realize multimodal anticounterfeiting using common light source {NIR (808 nm or 980 nm) laser and ultraviolet (UV) lamp}. These combined characteristics will be difficulty to forge and show high security in anticounterfeiting applications. A multimodal luminescent La 4 GeO 8 : Bi 3+ , Er 3+ phosphor • An advanced tunable multimodal luminescent La4GeO8: Bi3 + , Er3 + is developed. • The material could tune colors from white, blue-green, baby blue and orange yellow light under the increased excitation wavelength from 250 nm to 420 nm. • The phosphor also realizes successfully up conversion luminescence under the NIR (980 nm and 808 nm) laser irradiation. • The anticounterfeiting devices was easily detected by using a portable ultraviolet lamp or NIR (808 nm or 980 nm) laser and it was impossible to counterfeit by any substitute so far, which provided a high level of security.

Alkyl ammonium salt with different chain length for high-efficiency and good-stability 2D/3D hybrid perovskite solar cells

Recently, 2D/3D halide perovskites solar cells (PSCs) attract extensive attention due to simultaneous improved efficiency and stability. However, the types of alkyl ammonium salts, including the type of functional groups, the number of carbon atoms in the hydrocarbon chain, as well as the arrangement and distribution of the molecular structure, have a great impact on the performance and stability of films and devices. Herein, we compare the passivation capacity and moisture resistance of 2D capping layer based on three structurally similar alkyl ammonium salts (Butyl Ammonium Iodide (BAI), Propyl Ammonium Iodide (PAI), Ethyl Ammonium Iodide (EAI)) on triple cation perovskite thin films. As the number of carbon atoms in the alkane increases, the water contact angle gradually increases. Moreover, the defect state density is reduced to a certain extent compared to untreated 3D perovskite. The optimal PSCs with PAI-based 2D capping layer exhibit a power conversion efficiency (PCE) of 21.22% and remain 79.5% of initial PCE after 720 h. In addition, the reduced defect state density and improved crystallinity can be attributed to the hydrogen bonding interaction between the amine group and the [PbI 6 ] 4- framework. The emergence and development of 2D/3D perovskites have brought greater hope to commercialize the PSCs. • The NH · · · I hydrogen bond could reduce defects and inhibit ion migration. • PAI-based 2D/3D PSC achieved a PCE of 21.22%. • PAI-based 2D/3D PSC maintains 79.50% of the initial efficiency after 720 h. • The length of alkyl ammonium salts affects the humidity stability of perovskite.