Search

Abstract: A universal method to obtain record‐high electronic Seebeck coefficients is demonstrated while preserving reasonable conductivities in doped blends of organic semiconductors through rational design of the density of states (DOSs). A polymer semiconductor with a shallow highest occupied molecular orbital (HOMO) level‐poly(3‐hexylthiophene) (P3HT) is mixed with materials with a deeper HOMO (PTB7, TQ1) to form binary blends of the type P3HTx:B1‐x (0 ≤ x ≤ 1) that is p‐type doped by F4TCNQ. For B = PTB7, a Seebeck coefficient S = 1100 µV K−1 with conductivity σ = 0.3 S m−1 at x = 0.10 is achieved, while for B = TQ1, S = 2000 µV K−1 and σ = 0.03 S m−1 at x = 0.05 is found. Kinetic Monte Carlo simulations with parameters based on experiments show good agreement with the experimental results, confirming the intended mechanism. The simulations are used to derive a design rule for parameter tuning. These results can become relevant for low‐power, low‐cost applications like (providing power to) autonomous sensors, in which a high Seebeck coefficient translates directly to a proportionally reduced number of legs in the thermogenerator, and hence in reduced fabrication cost and complexity. [ABSTRACT FROM AUTHOR]

A low cost hydrothermal synthesis method to synthesize Mn-doped ZnO nanorods (NRs) with controllable morphology and structure has been developed. Ammonia is used to tailor the ammonium hydroxide concentration, which provides a source of OH- for hydrolysis and precipitation during the growth instead of HMT. The morphological, chemical composition, structural, and electronic structure studies of the Mn-doped ZnO NRs show that the Mn-doped ZnO NRs have a hexagonal wurtzite ZnO structure along the c-axis and the Mn ions replace the Zn sites in the ZnO NRs matrix without any secondary phase of metallic manganese element and manganese oxides observed. The fabricated PEDOT:PSS/Zn0.85Mn0.15O Schottky diode based piezoresistive sensor and UV photodetector shows that the piezoresistive sensor has pressure sensitivity of 0.00617 kPa-1 for the pressure range from 1 kPa to 20 kP and 0.000180 kPa-1for the pressure range from 20 kPa to 320 kPa with relatively fast response time of 0.03 s and the UV photodetector has both relatively high responsivity and fast response time of 0.065 A/W and 2.75 s, respectively. The fabricated Schottky diode can be utilized as a very useful human-friendly interactive electronic device for mass/force sensor or UV photodetector in everyday living life. This developed device is very promising for small-size, low-cost and easy-to-customize application-specific requirements. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Effects of in situ oxygen/water exposure on the energetics of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) films are presented. For oxygen exposure, the work function is downshifted by ≈0.15 eV compared to the ideal integer charge transfer (ICT) curve for pristine PCBM, which is incompatible with significant introduction of electron trap states or p‐doping. Water induces the highest occupied molecular orbital (HOMO) structure to undergo strong, irreversible modifications accompanied by a chemical interaction with PCBM. [ABSTRACT FROM AUTHOR]

The nature of the electronic and local magnetic properties of ferrocene (FeCp2) filled single-walled carbon nanotubes (SWCNT) has been investigated by X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Metallic, semiconducting, and unsorted ferrocene-filled tubes have been studied in different conditions of temperature and magnetic field. XMCD signal becomes evident with the application of a magnetic field at low temperature. We find that the molecular states of ferrocene interact with SWCNT of different metallicities. A paramagnetic behavior of encapsulated ferrocene is observed from the magnetic field dependent XMCD measurements which is consistent with theoretical predictions. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Energy levels and energy level alignment at interfaces play a decisive role in designing efficient and stable organic solar cells (OSCs). In this review two usually used technologies in organic photovoltaic communities for measuring energy levels of organic semiconductors, photoelectron spectroscopy and electrochemical methods, are introduced, and the relationships between the values obtained from the corresponding techniques are compared. The energy level and energy level alignment across the interfaces involved in solution processed organic photovoltaics are described, and the corresponding integer charge transfer model for predicting and explaining energy level alignment is presented. The effects of the interface properties in designing efficient binary and ternary OSCs were discussed. The effects of environmental factors mainly including water vapor, oxygen gas and thermal annealing on energy levels and energy level alignment involved in photoactive layers, and the subsequent effects on the corresponding OSC properties are given. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have demonstrated a high power conversion efficiency, however, the large energy loss due to non‐radiative recombination is the main challenge for further performance enhancement. Here, a surface treatment strategy is developed by heat‐induced decomposition of a thin interlayer 2,7‐Naphthaleneditriflate (NAP) to in situ reconstruct perovskite energetics. It is verified that the reconstructed perovskite surface energetics match better with the upper hole transport layer compared to the intrinsic condition. Spontaneous generation of n/n− homojunctions between the perovskite film bulk and the surface region promotes hole extraction, enhancing built‐in electric field, and thus significantly suppresses charge recombination at such perovskite hole‐selective heterojunctions. Moreover, the surface decomposed fluorine‐rich complexes passivate the defects and improve the crystallinity of the perovskite film. These advantages are confirmed by a remarkably improved efficiency from 20.52% for the control device to 23.37% for the treated one with excellent stability. The work provides a promising approach of in situ reconstructing perovskite surface and interface for the design of highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

No abstract is available for this article. [ABSTRACT FROM AUTHOR]

The development of highly efficient blue perovskite light‐emitting diodes (PeLEDs) remains a big challenge, requiring more fundamental investigations. In this work, significant photoluminescence enhancement in mixed halide blue perovskite films is demonstrated by using a molecule, benzylphosphonic acid, which eventually doubles the external quantum efficiency to 6.3% in sky‐blue PeLEDs. The photoluminescence enhancement is achieved by forming an oxide‐bonded perovskite surface at grain boundaries and suppressing electron–phonon interaction, which enhances the radiative recombination rate and reduces the nonradiative recombination rate, respectively. Moreover, severe thermal quenching is observed in the blue perovskite films, which can be explained by a two‐step mechanism involving exciton dissociation and electron–phonon interaction. The results suggest that enhancing the radiative recombination rate and reducing the electron–phonon interaction‐induced nonradiative recombination rate are crucial for achieving blue perovskite films with strong emission at or above room temperature. [ABSTRACT FROM AUTHOR]

Selective electron transport and extraction are essential to the operation of photovoltaic devices. Electron transport layer (ETL) is therefore critical to organic photovoltaics (OPV). Herein, an ETL configuration is presented comprising a solution‐processed n‐n organic heterojunction to enhance electron transport and hole blocking, and boost power conversion efficiency (PCE) in OPV. Specifically, the n‐n heterojunction is constructed by stacking a narrow‐band n‐type conjugated polymer layer (PNDIT‐F3N) and a wide‐band n‐type conjugated molecule layer (Phen‐NaDPO). Based on the ultraviolet photoelectron spectroscopy measurement and numerical simulation of current density‐voltage characteristics, the formation of the built‐in potential is investigated. In three OPVs with different active layers, substantial improvements are observed in performance following the introduction of this ETL configuration. The performance enhancement arises from the combination of selective carrier transport properties and reduced recombination. Another contributing factor is the good film‐forming quality of the new ETL configuration, where the surface energies of the related materials are well‐matched. The n‐n organic heterojunction represents a viable and promising ETL construction strategy for efficient OPV devices. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination at perovskite/charge transport layer heterojunction, seriously limiting their power conversion efficiencies. Herein, solution‐processed chromium multioxide (CrOx) is judiciously selected to construct a MAPbI3/CrOx/Spiro‐OMeTAD hole‐selective heterojunction. It is demonstrated that the inserted CrOx not only effectively reduces defect sites via redox shuttle at perovskite contact, but also decreases valence band maximum (VBM)‐HOMO offset between perovskite and Spiro‐OMeTAD. This will diminish thermionic losses for collecting holes and thus promote charge transport across the heterojunction, suppressing both defect‐assisted recombination and interface carrier recombination. As a result, a remarkable improvement of 21.21% efficiency with excellent device stability is achieved compared to 18.46% of the control device, which is among the highest efficiencies for polycrystalline MAPbI3 based n–i–p planar PSCs reported to date. These findings of this work provide new insights into novel charge‐selective heterojunctions for further enhancing efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) have the potential to revolutionize the field of organic bioelectronics. To date, most of the reported OECTs include p‐type (semi‐)conducting polymers as the channel material, while n‐type OECTs are yet at an early stage of development, with the best performing electron‐transporting materials still suffering from low transconductance, low electron mobility, and slow response time. Here, the high electrical conductivity of multi‐walled carbon nanotubes (MWCNTs) and the large volumetric capacitance of the ladder‐type π‐conjugated redox polymer poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n‐type OECTs with record‐high performance. It is demonstrated that the use of MWCNTs enhances the electron mobility by more than one order of magnitude, yielding fast transistor transient response (down to 15 ms) and high μC* (electron mobility × volumetric capacitance) of about 1 F cm−1 V−1 s−1. This enables the development of complementary inverters with a voltage gain of >16 and a large worst‐case noise margin at a supply voltage of <0.6 V, while consuming less than 1 µW of power. [ABSTRACT FROM AUTHOR]

Fluorescent nanohybrids, based on π‐extended hydroxyoxophosphole ligands grafted onto ZnO nanoparticles, are designed and studied. The restriction of the intramolecular motions of the organic fluorophore, through either aggregates' formation in solution or processing into thin films, forms highly emissive materials due to a strong aggregation induced emission effect. Theoretical calculations and XPS analyses were performed to analyze the interactions between the organic and inorganic counterparts. Preliminary results on the use of these nanohybrids as solution‐processed emissive layers in organic light emitting diodes (OLEDs) illustrate their potential for lighting applications. [ABSTRACT FROM AUTHOR]

Defect passivation via additive and energetic modification via interface engineering are two effective strategies for achieving high‐performance perovskite solar cells (PSCs). Here, the synergies of pentafluorophenyl acrylate when used as additive, in which it not only passivates surface defect states but also simultaneously modifies the energetics at the perovskite/Spiro‐OMeTAD interface to promote charge transport, are shown. The additive‐induced synergy effect significantly suppresses both defect‐assisted recombination and interface carrier recombination, resulting in a device efficiency of 22.42% and an open‐circuit voltage of 1.193 V with excellent device stability. The two photovoltaic parameters are among the highest values for polycrystalline CsFormamidinium/Methylammonium (FAMA)/FAMA based n‐i‐p structural PSCs using low‐cost silver electrodes reported to date. The findings provide a promising approach by choosing the dual functional additive to enhance efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

Defect passivation via additive and energetic modification via interface engineering are two effective strategies for achieving high‐performance perovskite solar cells (PSCs). Here, the synergies of pentafluorophenyl acrylate when used as additive, in which it not only passivates surface defect states but also simultaneously modifies the energetics at the perovskite/Spiro‐OMeTAD interface to promote charge transport, are shown. The additive‐induced synergy effect significantly suppresses both defect‐assisted recombination and interface carrier recombination, resulting in a device efficiency of 22.42% and an open‐circuit voltage of 1.193 V with excellent device stability. The two photovoltaic parameters are among the highest values for polycrystalline CsFormamidinium/Methylammonium (FAMA)/FAMA based n‐i‐p structural PSCs using low‐cost silver electrodes reported to date. The findings provide a promising approach by choosing the dual functional additive to enhance efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

Despite quick development of perovskite light‐emitting diodes (PeLEDs) during the past few years, the fundamental mechanisms on how ion migration affects device efficiency and stability remain unclear. Here, it is demonstrated that the dynamic redistribution of mobile ions in the emissive layer plays a key role in the performance of PeLEDs and can explain a range of abnormal behaviours commonly observed during the device measurement. The dynamic redistribution of mobile ions changes charge–carrier injection and leads to increased recombination current; at the same time, the ion redistribution also changes charge transport and results in decreased shunt resistance current. As a result, the PeLEDs show hysteresis in external quantum efficiencies (EQEs) and radiance, that is, higher EQEs and radiance during the reverse voltage scan than during the forward scan. In addition, the changes on charge injection and transport induced by the ion redistribution also well explain the rise of the EQE/radiance values under constant driving voltages. The argument is further rationalized by adding extra formamidinium iodide (FAI) into optimized PeLEDs based on FAPbI3, resulting in more significant hysteresis and shorter operational stability of the PeLEDs. [ABSTRACT FROM AUTHOR]

Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn4. The determined turnover frequency (TOF) for each active site of PtSn4 is 1.54 H2 s−1 at 100 mV. This sets a benchmark for HER catalysis on Pt‐based noble metals and earth‐abundant metal catalysts. We make use of the robust surface states of PtSn4 as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn4 displays excellent chemical and electrochemical stabilities after long‐term exposure in air and long‐time HER stability tests. [ABSTRACT FROM AUTHOR]

Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn4. The determined turnover frequency (TOF) for each active site of PtSn4 is 1.54 H2 s−1 at 100 mV. This sets a benchmark for HER catalysis on Pt‐based noble metals and earth‐abundant metal catalysts. We make use of the robust surface states of PtSn4 as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn4 displays excellent chemical and electrochemical stabilities after long‐term exposure in air and long‐time HER stability tests. [ABSTRACT FROM AUTHOR]

Abstract: The electrolysis processes such as hydrogen evolution reaction (HER) require high efficient catalysts with robust surface stability. A high conductivity is also necessary to speed up the charge transport between the catalyst and the electrolyte. Recently, the observation of exceedingly high conductivity in the topological semimetal MoP, has provided a model catalyst to investigate the correlation between the electrical transport and the electrocatalytic activity for the HER. Thus, MoP is encapsulated in a Mo, P codoped carbon layer (MoP@C). This composite material exhibits outstanding HER performance, with an extremely low overpotential of 49 mV at a current density of 10 mA cm−2 and a Tafel slope of 54 mV dec−1 in an alkaline medium. In addition, electron transport analysis indicates that MoP exhibits high conductivity and mobility due to the existence of triple‐point fermions and a complex Fermi surface. Furthermore, the presence of PC and MoC bonds at the interface between the carbon layer and the MoP particles modulates the band structure of MoP@C and facilitates fast electron transfer, accumulation, and subsequent delocalization, which are in turn responsible for the excellent HER activity. [ABSTRACT FROM AUTHOR]

A new strategy for designing ternary solar cells is reported in this paper. A low-bandgap polymer named PTB7-Th and a high-bandgap polymer named PBDTTS-FTAZ sharing the same bulk ionization potential and interface positive integer charge transfer energy while featuring complementary absorption spectra are selected. They are used to fabricate efficient ternary solar cells, where the hole can be transported freely between the two donor polymers and collected by the electrode as in one broadband low bandgap polymer. Furthermore, the fullerene acceptor is chosen so that the energy of the positive integer charge transfer state of the two donor polymers is equal to the energy of negative integer charge transfer state of the fullerene, enabling enhanced dissociation of all polymer donor and fullerene acceptor excitons and suppressed bimolecular and trap assistant recombination. The two donor polymers feature good miscibility and energy transfer from high-bandgap polymer of PBDTTS-FTAZ to low-bandgap polymer of PTB7-Th, which contribute to enhanced performance of the ternary solar cell. [ABSTRACT FROM AUTHOR]

A novel patterning technique of conductive polymers produced by vapor phase polymerization is demonstrated. The method involves exposing an oxidant film to UV light which changes the local chemical environment of the oxidant and subsequently the polymerization kinetics. This procedure is used to control the conductivity in the conjugated polymer poly(3,4-ethylenedioxythiophene):tosylate by more than six orders of magnitude in addition to producing high-resolution patterns and optical gradients. The mechanism behind the modulation in the polymerization kinetics by UV light irradiation as well as the properties of the resulting polymer are investigated. [ABSTRACT FROM AUTHOR]

In electronics, the field-effect transistor (FET) is a crucial cornerstone and successful integration of this semiconductor device into circuit applications requires stable and ideal electrical characteristics over a wide range of temperatures and environments. Solution processing, using printing or coating techniques, has been explored to manufacture organic field-effect transistors (OFET) on flexible carriers, enabling radically novel electronics applications. Ideal electrical characteristics, in organic materials, are typically only found in single crystals. Tiresome growth and manipulation of these hamper practical production of flexible OFETs circuits. To date, neither devices nor any circuits, based on solution-processed OFETs, has exhibited an ideal set of characteristics similar or better than today's FET technology based on amorphous silicon. Here, bar-assisted meniscus shearing of dibenzo-tetrathiafulvalene to coat-process self-organized crystalline organic semiconducting domains with high reproducibility is reported. Including these coatings as the channel in OFETs, electric field and temperature-independent charge carrier mobility and no bias stress effects are observed. Furthermore, record-high gain in OFET inverters and exceptional operational stability in both air and water are measured. [ABSTRACT FROM AUTHOR]

The semiconductor-electrode interface impacts the function and the performance of (opto)electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultrathin films on electrodes typically form islands due to dewetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultrathin conjugated polymer layers. Here, Langmuir-Shäfer-manufactured homogenous mono- and multilayers of semiconducting polymers on metal electrodes are reported and the energy level bending using photoelectron spectroscopy is tracked. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. These findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultrathin semiconducting polymers. [ABSTRACT FROM AUTHOR]

The color of polymer solar cells using an opaque electrode is given by the reflected light, which depends on the composition and thickness of each layer of the device. Metal-oxide-based optical spacers are intensively studied in polymer solar cells aiming to optimize the light absorption. However, the low conductivity of materials such as ZnO and TiO2 limits the thickness of such optical spacers to tenths of nanometers. A novel synthesis route of cluster-free Al-doped ZnO (AZO) nanocrystals (NCs) is presented for solution processing of highly conductive layers without the need of temperature annealing, including thick optical spacers on top of polymer blends. The processing of 80 nm thick optical spacers based on AZO nanocrystal solutions on top of 200 nm thick polymer blend layer is demonstrated leading to improved photocurrent density of 17% compared to solar cells using standard active layers of 90 nm in combination with thin ZnO-based optical spacers. These AZO NCs also open new opportunities for the processing of high-efficiency color tuned solar cells. For the first time, it is shown that applying solution-processed thick optical spacer with polymer blends of different thicknesses can process solar cells of similar efficiency over 7% but of different colors. [ABSTRACT FROM AUTHOR]

Organic photovoltaics are under intense development and significant focus has been placed on tuning the donor ionization potential and acceptor electron affinity to optimize open circuit voltage. Here, it is shown that for a series of regioregular-poly(3-hexylthiophene):fullerene bulk heterojunction (BHJ) organic photovoltaic devices with pinned electrodes, integer charge transfer states present in the dark and created as a consequence of Fermi level equilibrium at BHJ have a profound effect on open circuit voltage. The integer charge transfer state formation causes vacuum level misalignment that yields a roughly constant effective donor ionization potential to acceptor electron affinity energy difference at the donor-acceptor interface, even though there is a large variation in electron affinity for the fullerene series. The large variation in open circuit voltage for the corresponding device series instead is found to be a consequence of trap-assisted recombination via integer charge transfer states. Based on the results, novel design rules for optimizing open circuit voltage and performance of organic bulk heterojunction solar cells are proposed. [ABSTRACT FROM AUTHOR]

Preparation of size-tunable ultrathin W18O49 nanowires by an alcohol-assisted solvothermal decomposition of tungstic acid is reported. The synthesis of ultrathin W18O49 nanowires can be achieved at large scale and low cost, while changing the molecular size of the used alcohols can control the nanowire morphology. With increasing the molecular size of the alcohol, the synthesized W18O49 nanowires have smaller diameters and longer lengths. The as-prepared blue W18O49 nanomaterials show a very strong visible light absorption caused by oxygen defects and an aspect ratio-dependent photocatalytic activity on the degradation of pollutant rhodamine B (RhB) under simulated solar light irradiation. It is found that the W18O49 nanowires with highest aspect ratio show the highest activity in the photodegradation of RhB, which could be related to their higher density of oxygen surface defects in combination with a higher adsorption capability of RhB. This new synthetic route of size tunable ultrathin W18O49 nanomaterials will enlarge their potential applications and can be possibly used in the pyrolyzing synthesis of other metal oxide nanomaterials. [ABSTRACT FROM AUTHOR]

Ferromagnetic metal-organic semiconductor (FM-OSC) hybrid interfaces have been shown to play an important role for spin injection in organic spintronics. Here, 11,11,12,12-tetracyanonaptho-2,6-quinodimethane (TNAP) is introduced as an interfacial layer in Co-OSCs heterojunctions with an aim to tune the spin injection. The Co/TNAP interface is investigated by use of X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS), near edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD). Hybrid interface states (HIS) are observed at Co/TNAP interfaces, resulting from chemical interactions between Co and TNAP. The energy level alignment at the Co/TNAP/OSCs interface is also obtained, and a reduction of the hole injection barrier is demonstrated. XMCD results confirm sizeable spin polarization at the Co/TNAP hybrid interface. [ABSTRACT FROM AUTHOR]

Although the possibility of using metallocenes acting as n-type dopants for metallicity mixed and separated single-walled carbon nanotubes (SWCNT) has been proven, the question of usability for real-life applications still needs to be addressed. The most important factor for their applicability is the stability of the doping outside a vacuum environment. To clarify this issue we have conducted a long-term study on purely metallic SWCNTs after being filled with ferrocene and compared it to results after prolonged exposure to air, demonstrating a decomposition of about half of the filling material leaving a lower but stable doping state. The successful conversion to double-walled carbon nanotubes by high-temperature annealing yielding p-type doped hybrid structures is evidenced additionally. These results let us conclude that SWCNTs filled with metallocenes are an ideal n, or p-type doped starting material for applied electronics based on graphitic structures. [ABSTRACT FROM AUTHOR]

We study the filling of single-walled carbon nanotubes (SW- CNTs) with ferrocene molecules. Using e-DIPS SWCNTs with a mean diameter of 1.7 nm, we obtain a filling factor as high as 90%. At elevated temperatures in high vacuum the filled SWCNTs are transformed to double-walled carbon nanotubes (DWCNTs). Temperature dependence of inner tube growth is investigated by Raman spectroscopy. The electronic properties of the obtained nanostructures are studied by X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy. It is found that the growth temperature is higher for larger diameter inner tubes. It is demonstrated that ferrocene filling leads to electron doping of SWCNTs. [ABSTRACT FROM AUTHOR]

The cathode interface plays a critical role in achieving high‐performance fullerene/perovskite planar solar cells. Herein, the simple molecule Isatin and its derivatives are introduced at the back contact [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)/Al as a cathode modification interlayer. It is revealed that the Isatin interlayers facilitate electron transport/extraction and suppress electron recombination, attributed to the formation of negative dipole potential steps and the passivation of the interfacial trap density. The average power conversion efficiencies of the resulting devices are significantly improved by 11% from 17.68% to 19.74%, with an enhancement in all device parameters including short‐circuit current, open‐circuit voltage, and fill factor. The hysteresis index is found to disappear. In addition, such interlayer enhances device stability under ambient conditions compared to the control devices due to suppression of moisture‐induced degradation of the perovskite films. These findings provide a comprehensive understanding of the engineering of the back contact between PCBM and the metal electrode to improve efficiency and stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

The design of the earth‐abundant, nonprecious, efficient, and stable electrocatalysts for efficient hydrogen evolution reaction (HER) in alkaline media is a hot research topic in the field of renewable energies. A heterostructured system composed of MoSx deposited on NiO nanostructures (MoSx@NiO) as a robust catalyst for water splitting is proposed here. NiO nanosponges are applied as cocatalyst for MoS2 in alkaline media. Both NiO and MoS2@NiO composites are prepared by a hydrothermal method. The NiO nanostructures exhibit sponge‐like morphology and are completely covered by the sheet‐like MoS2. The NiO and MoS2 exhibit cubic and hexagonal phases, respectively. In the MoSx@NiO composite, the HER experiment in 1 m KOH electrolyte results in a low overpotential (406 mV) to produce 10 mA cm−2 current density. The Tafel slope for that case is 43 mV per decade, which is the lowest ever achieved for MoS2‐based electrocatalyst in alkaline media. The catalyst is highly stable for at least 13 h, with no decrease in the current density. This simple, cost‐effective, and environmentally friendly methodology can pave the way for exploitation of MoSx@NiO composite catalysts not only for water splitting, but also for other applications such as lithium ion batteries, and fuel cells. A heterostructured system composed of MoSx on NiO nanosponges is proposed as a robust catalyst for water splitting. The hydrogen evolution reaction in 1 m KOH electrolyte resulted in a low overpotential (406 mV) to produce a 10 mA cm−2 current density. The Tafel slope is 43 mV per decade, the lowest ever achieved for MoS2‐based electrocatalyst in alkaline media. [ABSTRACT FROM AUTHOR]

The cationic compositional engineered perovskites undergo severe degradation under illumination in ultrahigh vacuum (UHV) environment. As shown by Jianxin Tang, Qinye Bao and co‐workers in article number 1800262, UHV environment remarkably accelerates the degradation, which delivers the important message that current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space (e.g. satellites and probes). [ABSTRACT FROM AUTHOR]

Organometal halide perovskites exhibit a bright future for applications in solar cells, as efficiency has achieved over 22%. The long‐term stability remains a major obstacle for commercialization. Here, it is found that three cationic compositional engineered perovskites, MAPb(I0.83Br0.17)3, FA0.83MA0.17Pb(I0.83Br0.17)3, and Cs0.1(FA0.83MA0.17)0.9Pb(I0.83Br0.17)3, undergo severe degradation under white‐light illumination in ultrahigh vacuum (UHV) environment, but the rate of degradation is significantly lower for the mixed cation perovskites. This is attributed to the defect‐induced trap states that trigger the strong coupling between the photoexcited carriers and the crystal lattice. The observed behavior supports the view of the mixed cations suppressing the photoinduced degradation. It is further demonstrated that UHV environment remarkably accelerates the degradation of the perovskite films under illumination, which delivers a very important message that the current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space. Moreover, the applied UHV environment can be an accelerated test method to estimate the photostability of the perovskites. Photostability of mixed cation perovskite films in extreme environment is unraveled through ultrahigh vacuum (UHV) environment that simulates outer space. UHV remarkably accelerates the degradation of the perovskite films under white illumination, and it can be used as an accelerated test method to estimate the photostability of perovskites. [ABSTRACT FROM AUTHOR]