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Structuring metal halide perovskites with mixed halide anions is a promising strategy for attaining the desired bandgap and emission color for technological applications such as electroluminescent (EL) light‐emitting diodes (LEDs) and ultrahigh‐definition displays. However, these mixed halide perovskites suffer from severe EL spectral stability issues. During device operation, homogeneously mixed halide perovskite phases are prone to form halide‐segregated domain phases with spatially inhomogeneous bandgap and emission color, which hinders practical use of perovskite LEDs (PeLEDs). In this review, a comprehensive survey is performed about the underlying driving forces for phase segregation, and representative strategies are discussed for the development of color/spectral stable mixed halide PeLEDs. Finally, the future directions and prospects are outlined regarding further enhancement of the color/spectral stability of mixed halide PeLEDs. [ABSTRACT FROM AUTHOR]

In this work we performed dopant diffusion experiments on the hole transport material spiro-OMeTAD. Pure spiro-OMeTAD/F4-TCNQ doped spiro-OMeTAD and pure spiro-OMeTAD/DMC doped spiro-OMeTAD thin films were deposited on Au/Si(100) substrates. The energy levels, chemical states, and surface morphologies of formed films were studied by ultraviolet photoemission spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy as a function of the storage time in ultrahigh vacuum. We found only the pure spiro-OMeTAD/DMC doped spiro-OMeTAD film showed the n -type doping with the Fermi level of the film shifting away from the HOMO edge by 0.3 eV after 36 h. We propose that the diffusion of DMC dopant leads to the increase of the efficiencies of perovskite solar cell with the pin-hole free n-i-p structured hole transport layer several days after fabrication. [ABSTRACT FROM AUTHOR]

Solution-based n-doping of the polymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} [P(NDI2OD-T2)] and the small molecule 6,13-bis(tri(isopropyl)silylethynyl)pentacene (TIPS-pentacene) is realized with the air-stable dimers of rhodocene, [RhCp2]2, and ruthenium(pentamethylcyclopentdienyl)(1,3,5-triethylbenzene), [Cp*Ru(TEB)]2. Fermi level shifts, measured by direct and inverse photoemission spectroscopy, and orders of magnitude increase in current density and film conductivity point to strong n-doping in both materials. The strong reducing power of these air-stable dopants is demonstrated through the n-doping of TIPS-pentacene, a material with low electron affinity (3.0 eV). Doping-induced reduction of the hopping transport activation energy indicates that the increase in film conductivity is due in part to the filling of deep gap states by carriers released by the dopants. [ABSTRACT FROM AUTHOR]

Abstract: Atomic force microscopy (AFM) has found its applications in a wide range of research fields. In this review, we show by examples that atomic force microscopy is a powerful technique to investigate structural, mechanical and electrical properties of organic films. We start with an introduction of AFM instrumentation highlighting AFM developments that are of direct relevance to organic films. Next, we review AFM studies on organic films according to their preparation methods: self-assembly, the Langmuir–Blodgett technique, solution preparation, and thermal evaporation. In the discussion on self-assembled monolayers, we focus on aspects such as structural evolution, load-induced molecular tilting, annealing, and incorporation of conjugated groups. For solution prepared organic films, we stress annealing-induced structural evolution as well as the effects of phase separation/segregation. We also briefly summarize the progress of AFM investigation on Langmuir–Blodgett films and thermally evaporated organic films. We conclude the review by providing some thoughts for future exploration. In particular, atomic force microscopy combined with ultra-flat coplanar nano-electrodes provides a promising platform to isolate single or a small number of molecular features (e.g. vacancies, defects, grain boundaries) in organic films as well as to identify the role of these features at the nanometer scale. [Copyright &y& Elsevier]

Abstract: The electronic structure of the prototypical self-assembled monolayer (SAM) system, i.e. alkanethiol molecules on Au, is investigated via ultraviolet and inverse photoemission spectroscopy measurements. The determination of the density of filled and empty states of the system reveals that the metal Fermi level is significantly closer to the lowest unoccupied molecular orbital (LUMO) of the molecules than to their highest occupied molecular orbital (HOMO). The results suggest that charge carrier tunneling is controlled by the LUMO, rather than by the HOMO, in contrast to what is commonly assumed. [Copyright &y& Elsevier]

Abstract: In this work we demonstrate that the room-temperature deposition of the organic molecule 9,10-phenanthrenequinone (PQ) reduces the surface defect density of the silicon (100) surface by chemically bonding to the surface dangling bonds. Using various spectroscopic measurements we have investigated the electronic structure and band alignment properties of the PQ/Si interface. The band-bending at the PQ-passivated silicon surface is negligible for both n- and p-type substrates, demonstrating a low density of surface defects. Finally we show that PQ forms a semiconducting wide-bandgap type-I heterojunction with silicon. [Copyright &y& Elsevier]

Abstract: Temperature-dependent I–V measurements determine that pentacene is effectively p-doped by tetrafluoro-tetracyanoquinodimethane (F4-TCNQ). It has been shown by scanning tunneling microscopy (STM) that the donated hole is localized by the ionized dopant counter potential, and that the hole can be visualized . Here, it is argued that the effect of the localized hole on STM images should depend on distance as 1/ϵr, as per the Coulomb potential. By fitting line profiles of localized hole features to the Coulomb potential, it is shown that approximate values for the relative permittivity and Hubbard U of pentacene can be extracted. [ABSTRACT FROM AUTHOR]

The PL intensity of DMA0.11 is almost 2 times higher than MA1, and the PL decay lifetime of the DMA0.11 is also much longer than that of MA1, confirming reduced trap states after the incorporation of DMA. Apart from the reduction of defects, compared with the primary amine MA, the secondary amine DMA can increase the steric hindrance (Fig. By introducing the secondary amine molecule DMA, the perovskite solar cells (PSCs) achieved a power conversion efficiency of 21.6%. [Extracted from the article]

We demonstrate that holes from a p-doped N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layer transfer to an adjacent pentacene film. The spatial separation of carriers from dopants, or remote doping, is demonstrated with a combination of photoemission spectroscopy and current-voltage measurements for a p-doped α-NPD/pentacene heterojunction. Increased conductivity of the pentacene film is observed in both nongated temperature-dependent conductivity and gated thin-film transistor measurements. [ABSTRACT FROM AUTHOR]

Carrier diffusion length and lifetime parameters for electron transport at nanoscale semiconductor slabs have been fitted using a 1D model and the decay data extracted from transient photoemission electron microscopy. Meanwhile, a conventional photoluminescence quenching measurement needs two separate samples with an active material between blocking and quenching layers to characterize the carrier transport properties. In this work, only one few‐layer monocrystalline sample of γ‐InSe containing different thicknesses of active material is used to obtain a common diffusion coefficient consistent with previously reported values for vertical carrier diffusion in layered InSe. [ABSTRACT FROM AUTHOR]

Inverted positive‐intrinsic‐negative (p‐i‐n) perovskite solar cells (IPSCs) have attracted widespread attention due to their low fabrication temperature, good stability in ambient air, and the potential for use in flexible and tandem devices. In recent years, self‐assembled monolayers (SAMs) have been investigated as a promising hole‐selective contact for IPSCs, leading to an impressive record efficiency of about 26%, which is comparable to that of the regular n‐i‐p counterparts. This review focuses on the progress of SAM‐based IPSCs from the perspective of energy level matching, defect passivation, interface carrier extraction, and SAMs’ stability improvement, as well as the advances in up‐scalable fabrication of SAMs and perovskite layers for efficient solar modules and tandem devices. A cost analysis of the SAMs and other commonly used hole‐selective materials is conducted to evaluate their cost‐effectiveness for photovoltaic applications. Finally, the future challenges are pointed out and the perspectives on how to up‐scale SAM‐based IPSCs and improve their long‐term operational stability are provided. [ABSTRACT FROM AUTHOR]

In several photovoltaic (PV) technologies, the presence of electronic defects within the semiconductor band gap limit the efficiency, reproducibility, as well as lifetime. Metal halide perovskites (MHPs) have drawn great attention because of their excellent photovoltaic properties that can be achieved even without a very strict film‐growth control processing. Much has been done theoretically in describing the different point defects in MHPs. Herein, we discuss the experimental challenges in thoroughly characterizing the defects in MHPs such as, experimental assignment of the type of defects, defects densities, and the energy positions within the band gap induced by these defects. The second topic of this Review is passivation strategies. Based on a literature survey, the different types of defects that are important to consider and need to be minimized are examined. A complete fundamental understanding of defect nature in MHPs is needed to further improve their optoelectronic functionalities. [ABSTRACT FROM AUTHOR]

In zahlreichen Photovoltaik (PV)‐Technologien begrenzt das Vorhandensein elektronischer Defekte innerhalb der Halbleiter‐Bandlücke den Wirkungsgrad, die Reproduzierbarkeit und die Lebensdauer. Metallhalogenid‐Perowskite (MHPs) haben wegen ihrer hervorragenden Photovoltaik‐Eigenschaften, die auch ohne eine sehr strenge Filmwachstumskontrolle erreicht werden können, große Aufmerksamkeit gefunden. Es wurde in theoretischer Hinsicht viel getan, um die Punktdefekte in MHPs zu beschreiben. Dieser Aufsatz diskutiert die experimentellen Hürden für eine gründliche Charakterisierung der Defekte in MHPs, wie experimentelle Zuordnung der Defektart, Defektdichten und die durch diese Defekte induzierten Energiepositionen innerhalb der Bandlücke. Das zweite Schwerpunktthema sind die Passivierungsstrategien. Auf Grundlage einer Literaturrecherche werden die Defektenarten untersucht, die zu berücksichtigen und zu minimieren sind. Ein grundlegendes Verständnis der Defektbeschaffenheit von MHPs ist wünschenswert, um deren optoelektronische Funktionen zu verbessern. [ABSTRACT FROM AUTHOR]

Hybrid chemical vapor deposition (HCVD) is a promising method for the up‐scalable fabrication of perovskite solar cells/modules (PSCs/PSMs). However, the efficiency of the HCVD‐based perovskite solar cells still lags behind the solution‐processed PSCs/PSMs. In this work, the oxygen loss of the electron transport layer of SnO2 in the HCVD process and its negative impact on solar cell device performance are revealed. As the counter‐measure, potassium sulfamate (H2KNO3S) is introduced as the passivation layer to both mitigate the oxygen loss issue of SnO2 and passivate the uncoordinated Pb2+ in the perovskite film. In parallel, N‐methylpyrrolidone (NMP) is used as the solvent to dissolve PbI2 by forming the intermediate phase of PbI2•NMP, which can greatly lower the energy barrier for perovskite nucleation in the HCVD process. The perovskite seed is employed to further modulate the kinetics of perovskite crystal growth and improve the grain size. The resultant solar cells yield a champion power conversion efficiency (PCE) of 21.98% (0.09 cm2) with a stable output performance of 21.15%, and the PCEs of the mini‐modules are 16.16% (22.4 cm2, stable output performance of 14.72%) and 12.12% (91.8 cm2). Furthermore, the unencapsulated small area device shows an outstanding operational stability with a T80 lifetime exceeding 4000 h. [ABSTRACT FROM AUTHOR]

Mixing cations in the perovskite structure has been shown to improve optoelectronic device performance and stability. In particular, CsxMA1‐xPbBr3 (MA = CH3NH3) has been used to build high‐efficiency light‐emitting diodes. Despite those advantages, little is known about the exact location of the cations in the mixed perovskite film, and how cation distribution affects device properties and stability. By using scanning tunneling microscopy , the exact atomic structure of the mixed cation CsxMA1‐xPbBr3 perovskite interface is revealed. In addition, X‐ray photoelectron spectroscopy, ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are used to study the stability and electronic properties of the CsxMA1‐xPbBr3 perovskite film. Partial substitution of MA+ by Cs+ induces a modification of the perovskite surface structure, leading to improved device stability is shown. These results provide a better understanding of the key parameters involved in the stability of mixed cation perovskite solar cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface degradation process of the lithium-layered transition metal oxide cathode is revealed by an operando Raman spectroscopy study. • The degradation process is visualized by Raman mapping with the spectral window of ∼600 cm−1. • The degradation process not only involves the structural changes, but also the growth and merging between the degenerated layers on charge–discharge. • The present study offers crucial information to counter the capacity decay of the NMC batteries. The well-defined layered structure for Li+ (de)intercalation of transition metal oxide cathodes plays a crucial role in delivering high capacity for lithium-ion batteries. Therefore, structural deformations of the layered structure are often considered as the evidence of deterioration in the battery performance and stability. In this study, the surface degradation mechanism of the layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode is examined on charge–discharge using an operando Raman cell. We revealed the surface degradation process of the cathode with the A 1g Raman spectral window (∼600 cm−1) in the voltage range of 2.8–4.35 V, and proposed the nucleation-merging mechanism. The spectral shifts and mappings have been compared between the early-stage and later-stage cycles (≥15 cycles). It has been identified that the degradation process not only involves the structural changes (i.e., nucleation of the degenerated layers), but also the growth/merging between the degenerated layers during charge and discharge. This observation provides key information on how the reconstructed surface can expand during cycling. [ABSTRACT FROM AUTHOR]

Metal halide perovskite solar cells have made significant breakthroughs in power conversion efficiency and operational stability in the last decade, thanks to the advancement of perovskite deposition methods. Solution-based methods have been intensively investigated and deliver record efficiencies. On the other hand, vapor deposition-based and assisted methods were less studied in the early years but have received more attention recently due to their great potential toward large-area solar module manufacturing and high batch-to-batch reproducibility. In addition, an in-depth understanding of perovskite crystallization kinetics during the vapor deposition based and assisted process allows increasing perovskite deposition rate and enhancing perovskite quality. In this review, the advances in vapor-based and assisted methods for the fabrication of perovskite solar cells are introduced. The quality of the perovskite layers (i.e., morphology, crystallinity, defect chemistry, carrier lifetime) fabricated by different methods is compared. The limitations of state-of-the-art vapor-deposited perovskite layers are discussed. Finally, insights into the engineering of vapor deposition based and assisted perovskite layers toward efficient and stable perovskite solar cells and modules are provided. [ABSTRACT FROM AUTHOR]

Polycrystalline properties of perovskites can induce the growth of different nanostructures, thanks to their facile fabrication. In this work, the CsPb2Br5 perovskite grains were used as templates to induce the growth of the ring-like structures on a SiO2/Si substrate. Owing to the oxidation of the volatile PbBr2 originated from the decomposition of CsPb2Br5, the grain boundaries of perovskites are prone to reaction with SiO2, which leads to the formation of Pb-silicate glass at high temperatures. The quasi-circular grain structure of CsPb2Br5 defines the final dimension of the Pb-silicate glass ring-like structures. X-ray photoelectron spectroscopy (XPS) measurement results reveal the formation and composition of the Pb-silicate glass ring-like structures converting from the halide perovskite film on the SiO2/Si substrate. Furthermore, these ring-like structures can extend to the field of display and pulsed-laser by combining existing techniques. [ABSTRACT FROM AUTHOR]

Highlights: A novel strategy to further improve the efficiency of lead-free tin perovskite solar cells by carefully controlling the built-in electric field in the absorber is described. A promising efficiency of 13.82% was obtained based on the formamidinium tin iodide (FASnI3) perovskite solar cells with a vertical Sn2+ gradient and an enhanced electric field. The solar cell with a heterogeneous FASnI3 absorber is ultrastable, maintaining over 13% efficiency after operation under 1-sun illumination for 1,000 h in air. Lead-free tin perovskite solar cells (PSCs) have undergone rapid development in recent years and are regarded as a promising eco-friendly photovoltaic technology. However, a strategy to suppress charge recombination via a built-in electric field inside a tin perovskite crystal is still lacking. In the present study, a formamidinium tin iodide (FASnI3) perovskite absorber with a vertical Sn2+ gradient was fabricated using a Lewis base-assisted recrystallization method to enhance the built-in electric field and minimize the bulk recombination loss inside the tin perovskites. Depth-dependent X-ray photoelectron spectroscopy revealed that the Fermi level upshifts with an increase in Sn2+ content from the bottom to the top in this heterogeneous FASnI3 film, which generates an additional electric field to prevent the trapping of photo-induced electrons and holes. Consequently, the Sn2+-gradient FASnI3 absorber exhibits a promising efficiency of 13.82% for inverted tin PSCs with an open-circuit voltage increase of 130 mV, and the optimized cell maintains over 13% efficiency after continuous operation under 1-sun illumination for 1,000 h. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials (MHPMs) have attracted significant attention because of their superior optoelectronic properties and versatile applications. The power conversion efficiency of MHPM solar cells (PSCs) has skyrocketed to 25.5 %. Although the performance of PSCs is already competitive, several important challenges still need to be solved to realize commercial applications. A thorough understanding of surface atomic structures and structure–property relationships is at the heart of these remaining issues. Scanning tunneling microscopy (STM) and spectroscopy (STS) can be used to characterize the surface properties of MHPMs, which can offer crucial insights into MHPMs at the atomic scale. This Review summarizes recent progress in STM and STS studies on MHPMs, with a focus on the surface properties. We provide understanding from the comparative perspective of several different MHPMs. We also highlight a series of novel phenomena observed by STM and STS. Finally, we outline a few research topics of primary importance for future studies. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials (MHPMs) have attracted significant attention because of their superior optoelectronic properties and versatile applications. The power conversion efficiency of MHPM solar cells (PSCs) has skyrocketed to 25.5 %. Although the performance of PSCs is already competitive, several important challenges still need to be solved to realize commercial applications. A thorough understanding of surface atomic structures and structure–property relationships is at the heart of these remaining issues. Scanning tunneling microscopy (STM) and spectroscopy (STS) can be used to characterize the surface properties of MHPMs, which can offer crucial insights into MHPMs at the atomic scale. This Review summarizes recent progress in STM and STS studies on MHPMs, with a focus on the surface properties. We provide understanding from the comparative perspective of several different MHPMs. We also highlight a series of novel phenomena observed by STM and STS. Finally, we outline a few research topics of primary importance for future studies. [ABSTRACT FROM AUTHOR]

The buried interface between the perovskite and the electron transport layer (ETL) plays a vital role for the further improvement of power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). However, it is challenging to efficiently optimize this interface as it is buried in the bottom of the perovskite film. Herein, a buried interface strengthening strategy for constructing efficient and stable PSCs by using CsI‐SnO2 complex as an ETL is reported. The CsI modification facilitates the growth of the perovskite film and effectively passivates the interfacial defects. Meanwhile, the gradient distribution of Cs+ contributes to a more suitable band alignment with the perovskite, and the incorporation of Cs+ into the perovskite at the bottom interface enhances the resistance against UV illumination. Eventually, a significantly improved PCE up to 23.3% and a much‐enhanced UV stability of FAPbI3‐based PSCs are achieved. This work highlights the importance of cesium‐enhanced interfaces and provides an effective approach for the simultaneous realization of highly efficient and UV‐stable perovskite solar cells. [ABSTRACT FROM AUTHOR]

In order to purify phosphoric acid, the suspension melt crystallization process was studied. The suspension crystallization experiments were carried out with 80, 84 and 88 wt% phosphoric acid melt at the cooling rates of 0.05, 0.1 and 0.2 K/min, respectively. Sweating experiments were executed for various crystals obtained in suspension crystallization step. The purification effects of the sweating parameters including sweating time, initial inclusion amount and initial impurity content were studied. The inclusion fraction increases with the increase in cooling rate. The inclusion fraction of the crystals which were formed with feed concentration of 84 wt% phosphoric acid melt is lowest among the three feed concentrations. Different impurities have different purification performances during sweating. High inclusion amount and low impurity concentration favor the purification of H3PO4·0.5H2O crystals during sweating. [ABSTRACT FROM AUTHOR]

Abstract: We report on the effect of the deposition of self-assembled monolayers (SAMs) on the source and drain electrodes on the contact resistance and mobility in organic thin film transistors (OTFTs). Ultraviolet photoelectron spectroscopy (UPS) shows a variation of the work function of the electrodes depending on the SAM. OTFTs were fabricated with solution processible Polyera ActivInk™ N1400, TIPS-pentacene and TFB, giving access to both polarities of transistors and to both crystalline and amorphous materials. The transfer line method (TLM) was used to separately estimate the contact resistance and mobility. A clear correlation is found between the work function of the modified electrodes and the corresponding contact resistance. The effect on mobility is more puzzling, and tentatively attributed to morphological effects. [Copyright &y& Elsevier]

Perovskite light‐emitting diodes (PeLEDs) have attracted attention because of their high efficiencies. However, due to the sensitivity of perovskites to ambient condition, perovskite emitter layers are generally fabricated under an inert gas environment (e.g., dry N2), which increases processing complexity and cost. Here, air‐prepared quasi‐2D perovskites are reported for efficient PeLEDs. It is found that the phase aggregation is the major obstacle deteriorating the characteristics of air‐prepared perovskites. Through antisolvent engineering to modulate the nucleation and growth characteristics of perovskite films from precursor solution, phase aggregations are restrained. Confocal laser scanning fluorescence microscopy results demonstrate homogeneous perovskite films with uniform photoluminescence distributions. Traps at grain boundaries are passivated, and exciton transfer among perovskite phases becomes effective. Finally, efficient green PeLEDs based on air‐prepared perovskites are realized with an external quantum efficiency of 15.4%. This work provides a promising strategy to fabricate cost‐effective perovskite devices in ambient air condition. [ABSTRACT FROM AUTHOR]

Upscaling efficient and stable perovskite layers is one of the most challenging issues in the commercialization of perovskite solar cells. Here, a lead halide–templated crystallization strategy is developed for printing formamidinium (FA)–cesium (Cs) lead triiodide perovskite films. High-quality large-area films are achieved through controlled nucleation and growth of a lead halide•N-methyl-2-pyrrolidone adduct that can react in situ with embedded FAI/CsI to directly form a-phase perovskite, sidestepping the phase transformation from d-phase. A nonencapsulated device with 23% efficiency and excellent long-term thermal stability (at 85°C) in ambient air (~80% efficiency retention after 500 hours) is achieved with further addition of potassium hexafluorophosphate. The slot die–printed minimodules achieve champion efficiencies of 20.42% (certified efficiency 19.3%) and 19.54% with an active area of 17.1 and 65.0 square centimeters, respectively. [ABSTRACT FROM AUTHOR]

In addition to high efficiencies, upscaling and long‐term operational stability are key pre‐requisites for moving perovskite solar cells toward commercial applications. In this work, a strategy to fabricate large‐area uniform and dense perovskite films with a thickness over one‐micrometer via a two‐step coating process by introducing NH4Cl as an additive in the PbI2 precursor solution is developed. Incorporation of NH4Cl induces the formation of the intermediate phases of x[NH4+]·[PbI2Clx]x− and HPbI3−xClx, which can effectively retard the crystallization rate of perovskite leading to uniform and compact full‐coverage perovskite layers across large areas with high crystallinity, large grain sizes, and small surface roughness. The 5 × 5 and 10 × 10 cm2 perovskite solar modules (PSMs) based on this method achieve a power conversion efficiency (PCE) of 14.55% and 10.25%, respectively. These PSMs also exhibit good operational stability with a T80 lifetime (the time during which the solar module PCE drops to 80% of its initial value) under continuous light illumination exceeding 1600 h (5 × 5 cm2) and 1100 h (10 × 10 cm2), respectively. [ABSTRACT FROM AUTHOR]

Highlights: High-quality large-area SnO2 films are fabricated by chemical bath deposition with the addition of KMnO4. The presence of K and Mn ions can improve both the crystallinity and the phase stability of perovskites and reduce hysteresis of devices simultaneously. Perovskite solar modules (22.4 and 91.8 cm2) are demonstrated with active area efficiencies of 17.26% and 13.72%, respectively, and the 22.4 cm2 perovskite solar module exhibits a T80 operation lifetime exceeding 1000 h in ambient condition.Tin dioxide (SnO2) has been demonstrated as one of the promising electron transport layers for high-efficiency perovskite solar cells (PSCs). However, scalable fabrication of SnO2 films with uniform coverage, desirable thickness and a low defect density in perovskite solar modules (PSMs) is still challenging. Here, we report preparation of high-quality large-area SnO2 films by chemical bath deposition (CBD) with the addition of KMnO4. The strong oxidizing nature of KMnO4 promotes the conversion from Sn(II) to Sn(VI), leading to reduced trap defects and a higher carrier mobility of SnO2. In addition, K ions diffuse into the perovskite film resulting in larger grain sizes, passivated grain boundaries, and reduced hysteresis of PSCs. Furthermore, Mn ion doping improves both the crystallinity and the phase stability of the perovskite film. Such a multifunctional interface engineering strategy enabled us to achieve a power conversion efficiency (PCE) of 21.70% with less hysteresis for lab-scale PSCs. Using this method, we also fabricated 5 × 5 and 10 × 10 cm2 PSMs, which showed PCEs of 15.62% and 11.80% (active area PCEs are 17.26% and 13.72%), respectively. For the encapsulated 5 × 5 cm2 PSM, we obtained a T80 operation lifetime (the lifespan during which the solar module PCE drops to 80% of its initial value) exceeding 1000 h in ambient condition. [ABSTRACT FROM AUTHOR]

Highlights: Recent progress of efficiency and long-term stability for perovskite solar cells, and the development of perovskite-based tandem solar cells are described. The progress of lead-free perovskite solar cells and their potential for industrial production are discussed in detail. The current status, ongoing challenges, and the future outlooks of perovskite solar cells are highlighted.Perovskite solar cells (PSCs) emerging as a promising photovoltaic technology with high efficiency and low manufacturing cost have attracted the attention from all over the world. Both the efficiency and stability of PSCs have increased steadily in recent years, and the research on reducing lead leakage and developing eco-friendly lead-free perovskites pushes forward the commercialization of PSCs step by step. This review summarizes the main progress of PSCs in 2020 and 2021 from the aspects of efficiency, stability, perovskite-based tandem devices, and lead-free PSCs. Moreover, a brief discussion on the development of PSC modules and its challenges toward practical application is provided. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have emerged as the next‐generation high‐efficiency solar cell, but their absorption is mostly limited to the visible (vis) range. One possible solution is to integrate near‐infrared (NIR)‐to‐vis photon upconversion (UC). Herein, we show the first example of endowing perovskite solar cells with NIR sensitivity by using solid films showing NIR‐to‐vis UC based on triplet‐triplet annihilation (TTA). A high TTA‐UC efficiency of 4.1±0.3 % at an excitation intensity of 125 W/cm2 is achieved by sensitizing a rubrene (acceptor) triplet with an osmium (Os) complex donor having singlet‐to‐triplet (S−T) absorption in the NIR range, and by increasing the fluorescence quantum yield through energy harvesting to a highly fluorescent collector. In particular, our spectroscopic studies indicate that the upconverted acceptor singlet energy is almost selectively transferred to the collector rather than being quenched by the donor. By attaching the TTA‐UC film behind a semi‐transparent perovskite solar cell, a photocurrent generation is observed under excitation at 938 nm. [ABSTRACT FROM AUTHOR]

A large number of derivative phases in inorganic perovskites are reported with special structures and extraordinary performances in photoelectronic device applications. The reverse phase transition between derivative phases and perovskites usually induces recrystallization or forms mixed components. In this work, derivative phase‐induced growth of the CsPbBr3 micro–nanowire (MW) array by utilizing phase transition of the 2D CsPb2Br5 phase is reported. Owing to its layered structure and phase transition, annealing of CsPb2Br5 at a temperature of 550 °C combined with solvent quenching leads to a templating effect to form a high‐quality CsBr MW array. Subsequent PbBr2 deposition and the second annealing are employed to form aligned CsPbBr3 MW arrays. Based on this method, a CsPbBr3 MW array‐based photodetector is fabricated. The large grain size, less grain boundaries, and lower surface potential of the CsPbBr3 MW array lead to high device performance with a responsivity of 7.66 A W−1, a detectivity of ≈1012 Jones, and long‐term operational stability over 1900 min. [ABSTRACT FROM AUTHOR]

Solar cells based on metal halide perovskites have emerged as a promising low‐cost photovoltaic technology. In contrast to inert atmospheres where most of the lab‐scale devices are made to date, large‐area low‐cost production of perovskite solar cells often involves processing of perovskites in various atmospheres including ambient air, nitrogen, and/or vacuum. Herein, the impact of atmosphere on the energy levels of methylammonium lead halide perovskite films is systematically investigated. The atmosphere is varied to simulate the typical fabrication process. Through a comprehensive analysis combining the Fermi level evolution, surface photovoltage, photoluminescence properties, photovoltaic performance, and device simulation, an overall landscape of the energy diagram of the perovskite layer is able to be determined. The findings have direct implications for real‐world devices under typical atmospheres, and provide insights into the fabrication‐process design and optimization. Furthermore, a universal Fermi level shift under vacuum for lead halide‐based perovskites revealed in this study, urges a refreshed view on the energetics studies conducted without considering the atmospheric effect. [ABSTRACT FROM AUTHOR]

ABX3 type metal halide perovskite solar cells (PSCs) have shown efficiencies over 25%, rocketing toward their theoretical limit. To gain the full potential of PSCs relies on the understanding of the device working mechanisms and recombination, the material quality, and the match of energy levels in the device stacks. In this review, the importance of designing PSCs from the viewpoint of surface/interface science studies is presented. For this purpose, recent case studies are discussed to demonstrate how probing of local heterogeneities (e.g., grains, grain boundaries, atomic structure, etc.) in perovskites by surface science techniques can help correlate material properties and PSC device performance. At the solar cell device level with active areas larger than millimeter scale, the ensemble average measurement techniques can characterize the overall average properties of perovskite films as well as their adjacent layers and provide clues to understand better the solar cell parameters. How generation and healing of electronic defects in perovskite films limit the device efficiency, reproducibility, and stability, and induce the time‐dependent transient behavior in the current‐voltage curves are also the central focus of this review. On the basis of these studies, strategies to further improve efficiency and stability, as well as reducing hysteresis are presented. [ABSTRACT FROM AUTHOR]

In the past decade, the efficiency of perovskite solar cells quickly increased from 3.8% to 25.2%. The quality of perovskite films plays vital role in device performance. The films fabricated by solution‐process are usually polycrystalline, with significantly higher defect density than that of single crystal. One kind of defect in the films is uncoordinated Pb2+, which is usually generated during thermal annealing process due to the volatile organic component. Another detrimental kind of defect is Pb0, which is often observed during the film fabrication process or solar cell operation. Because the open circuit voltage has a close relation with the defect density, it is thus desirable to passivate these two kinds of defects. Here, a molecule with multiple ligands is introduced, which not only passivates the uncoordinated Pb2+ defects, but also suppresses the formation of Pb0 defects. Meanwhile, such a treatment improves the energy level alignment between the valence band of perovskite and the highest occupied molecular orbital of spiro‐OMeTAD. As a result, the performance of perovskite solar cells significantly increases from 19.0% to 21.4%. [ABSTRACT FROM AUTHOR]

Although b-CsPbI3 has a bandgap favorable for application in tandem solar cells, depositing and stabilizing b-CsPbI3 experimentally has remained a challenge. We obtained highly crystalline b-CsPbI3 films with an extended spectral response and enhanced phase stability. Synchrotron-based x-ray scattering revealed the presence of highly oriented b-CsPbI3 grains, and sensitive elemental analyses—including inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry—confirmed their all-inorganic composition. We further mitigated the effects of cracks and pinholes in the perovskite layer by surface treating with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment between the b-CsPbI3 absorber layer and carrier-selective contacts. The perovskite solar cells made from the treated material have highly reproducible and stable efficiencies reaching 18.4% under 45 ± 5°C ambient conditions. [ABSTRACT FROM AUTHOR]

The family of soluble fullerene derivatives comprises a widely studied group of electron transporting molecules for use in organic electronic and optoelectronic devices. For electronic applications, electron transporting (n-channel) materials are required for implementation into organic complementary logic circuit architectures. To date, few soluble candidate materials have been studied that fulfill the stringent requirements of high carrier mobility and air stability. Here we present a study of three soluble fullerenes with varying electron affinity to assess the impact of electronic structure on device performance and air stability. Through theoretical and experimental analysis of the electronic structure, characterization of thin-film structure, and characterization of transistor device properties we find that the air stability of the present series of fullerenes not only depends on the absolute electron affinity of the semiconductor but also on the disorder within the thin-film. [ABSTRACT FROM AUTHOR]

The corrected text is below, For ligand modification, 0.5 mg pentaerythritol tetrakis(3-mercaptopropionate) (ML) is dissolved in 1 mL CB and spun on top of perovskite, These errors do not affect the conclusions of the report. In the supporting information file of the same manuscript, on Page 2, in the "Device fabrication" an error related to the protocol for ligand modification was made. [Extracted from the article]

Carbon aerogel prepared using waste biomass as the carbon source can be utilized as the ideal absorption material for the remediation of oil spill accidents. However, the brittleness of the fiber and agglomeration of precursor fiber chains due to hydrogen bonding leads to poor mechanical properties and low absorption capacity of the carbon aerogel. The doping treatment used to overcome such defects still shows some deficiencies, such as high cost, cumbersome process, and part of the process involving toxicity. To overcome the agglomeration between the cellulose chains, a chemically-etched biomass-based carbon aerogel (EBCA) was prepared using pineapple cellulose nanofiber (CNF) etched by the deep eutectic solvents (DES) of choline chloride/urea under a low carbonization temperature of 400 °C. The as-prepared material, designated as EBCA-400, possesses a 3D structure with a huge BET specific surface area of 501.56 m2 g−1, a density of only 0.032 g cm−3 and a porosity of 97.3% with excellent elasticity performance and self-recovery performance owing to the enhancement of the surface roughness of fibers through DES etching. Also, EBCA-400 shows a superhydrophobicity with a water contact angle (WCA) of 157.6° and has a strong and fast absorption capacity for various oils in various scenarios, the absorption capacity for CCl 4 reaches 288 times its own weight, and the absorption efficiency to CCl 4 can still reach more than 97% of the maximum value even after 15 oil absorption-removal cycles. With the characteristics of very low density, huge porosity, excellent elasticity and superhydrophobicity as well as better reusability, EBCA-400 has great potential in oil spill remediation. This study provides a convenient and environment-friendly way for surface modification to improve the elasticity of carbon aerogel, which is crucial to the recovery of carbon aerogel for its reusability. [Display omitted] • EBCA-400 was prepared at a lower carbonization temperature. • Chemical etching imparts EBCA-400 excellent elasticity. • EBCA-400 possesses superhydrophobicity with WCA as high as 157.6°. • EBCA-400 shows excellent absorbency to various oils and reusability. [ABSTRACT FROM AUTHOR]

Abstract: In this work all‐inorganic perovskite CsPbIBr2 are doped with Mn to compensate their shortcomings in band structure for the application of perovskite solar cells (PSCs). The novel Mn‐doped all‐inorganic perovskites, CsPb1−xMnxI1+2xBr2−2x, are prepared in ambient atmosphere. As the concentration of Mn2+ ions increases, the bandgaps of CsPb1−xMnxI1+2xBr2−2x decrease from 1.89 to 1.75 eV. Additionally, when the concentration of Mn dopants is appropriate, this novel Mn‐doped all‐inorganic perovskite film shows better crystallinity and morphology than its undoped counterpart. These advantages alleviate the energy loss in hole transfer and facilitate the charge‐transfer in perovskites, therefore, PSCs based on these novel CsPb1−xMnxI1+2xBr2−2x perovskite films display better photovoltaic performance than the undoped CsPbIBr2 perovskite films. The reference CsPbIBr2 cell reaches a power conversion efficiency (PCE) of 6.14%, comparable with the previous reports. The CsPb1−xMnxI1+2xBr2−2x cells reach the highest PCE of 7.36% (when x = 0.005), an increase of 19.9% in PCE. Furthermore, the encapsulated CsPb0.995Mn0.005I1.01Br1.99 cells exhibit good stability in ambient atmosphere. The storage stability measurements on the encapsulated PSCs reveal that PCE is dropped by only 8% of the initial value after >300 h in ambient. Such improved efficiency and stability are achieved using low‐cost carbon electrodes (without expensive hole transport materials and Au electrodes). [ABSTRACT FROM AUTHOR]

A multi-layer of stacked-graphene (8 layers of basal planes) grown by chemical vapour deposition (CVD) is introduced as an artificial solid electrolyte interphase (SEI) layer onto a transition metal oxide cathode for lithium-ion batteries. The basal planes are generally regarded as a strong physical barrier that prevents lithium-ion diffusion, although it is believed that a small number of lithium-ions can migrate through the defect sites of the stacked layers. Interestingly, the unique design of the stacked-graphene perpendicular to the basal planes not only effectively suppresses the formation of instable SEI layers, but also achieves a reasonable amount of battery charge capacities. To correctly understand the impact from the stacked design, we further studied the rate kinetics difference between slow cycles (0.125 C→0.250 C→0.400 C→0.125 C) and rapid cycles (C→2 C→3 C→C). We propose that the clap-net like design of the stacked-graphene could enable the effective conducting pathway for electron transport, while protecting the active material inside. The magnetic measurements reveal the efficient Li + (de)intercalation into graphene-layers. The artificial SEI also renders the electrode/electrolyte interface more stable against dynamic rate changes. The present approach provides a particular advantage in developing high stability battery that can be utilized at various charge rates. [ABSTRACT FROM AUTHOR]

To achieve industrially viable fabrication process for perovskite-based solar cells, every process step must be optimized for maximum throughput. We present a study of substituting laboratory-type UV-Ozone surface treatment with a high-throughput Corona treatment in a scalable perovskite solar cell fabrication process. It is observed that water contact angle measurements provide insufficient information to determine the necessary dose of Corona or UV-Ozone treatment, but the surface carbon signal measured by x-ray photoelectron spectroscopy accurately identifies when surface contamination has been completely removed. Furthermore, we observe highly accelerated de-contamination of ZnO surfaces by UV-Ozone treatment. The effect can be explained by photocatalytic O 2 − ion generation indicating that UV-Ozone treatment is also applicable in high-throughput processing. [ABSTRACT FROM AUTHOR]

Semitransparent perovskite solar cells (st-PSCs) have received remarkable interest in recent years because of their great potential in applications for solar window, tandem solar cells, and flexible photovoltaics. However, all reported st-PSCs require expensive transparent conducting oxides (TCOs) or metal-based thin films made by vacuum deposition, which is not cost effective for large-scale fabrication: the cost of TCOs is estimated to occupy ≈75% of the manufacturing cost of PSCs. To address this critical challenge, this study reports a low-temperature and vacuum-free strategy for the fabrication of highly efficient TCO-free st-PSCs. The TCO-free st-PSC on glass exhibits 13.9% power conversion efficiency (PCE), and the four-terminal tandem cell made with the st-PSC top cell and c-Si bottom cell shows an overall PCE of 19.2%. Due to the low processing temperature, the fabrication of flexible st-PSCs is demonstrated on polyethylene terephthalate and polyimide, which show excellent stability under repeated bending or even crumbing. [ABSTRACT FROM AUTHOR]

Mixed cation hybrid perovskites such as Cs xFA1− xPbI3 are promising materials for solar cell applications, due to their excellent photoelectronic properties and improved stability. Although power conversion efficiencies (PCEs) as high as 18.16% have been reported, devices are mostly processed by the anti-solvent method, which is difficult for further scaling-up. Here, a method to fabricate Cs xFA1− xPbI3 by performing Cs cation exchange on hybrid chemical vapor deposition grown FAPbI3 with the Cs+ ratio adjustable from 0 to 24% is reported. The champion perovskite module based on Cs0.07FA0.93PbI3 with an active area of 12.0 cm2 shows a module PCE of 14.6% and PCE loss/area of 0.17% cm−2, demonstrating the significant advantage of this method toward scaling-up. This in-depth study shows that when the perovskite films prepared by this method contain 6.6% Cs+ in bulk and 15.0% at the surface, that is, Cs0.07FA0.93PbI3, solar cell devices show not only significantly increased PCEs but also substantially improved stability, due to favorable energy level alignment with TiO2 electron transport layer and spiro-MeOTAD hole transport layer, increased grain size, and improved perovskite phase stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Perovskite nanocrystals-polycarbonate composite films was patterned in three level. • Destroy the composite in high power to present the patterns in bright field. • Damage the nanocrystals in medium power to quench the fluorescence permanently. • Induce defects in low power to quench the fluorescence temporarily. • Water immersion allowed defects passivation and local fluorescence recovery. Ensuring the concealment and integrity of the loaded information during delivery remains a key challenge to cryptography. In this study, we synthesized CsPbBr 3 nanocrystals-polycarbonate composite films using the swelling-deswelling method, improved the stability and maintained the flexibility of the polymer. More importantly, we developed a novel patterning method using a nanosecond laser to engrave the composite selectively in three power grades: destroy the composite in high-power to present the patterns in bright field; damage the nanocrystals in medium-power to quench the fluorescence permanently; induce some defects to the nanocrystals in low-power to quench the fluorescence temporarily. A subsequent water immersion process allowed trace water penetration to passivate defects and recover the fluorescence locally to present the encrypted information. Our technology shows excellent performance by triple encryption level, convenient decryption (ultraviolet and water), low cost (2.8 × 10-3 USD/cm2) and high precision (minimum patterning size down to 15 μm). [ABSTRACT FROM AUTHOR]

Doping properties of 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene(spiro-MeOTAD) hole transport layer are investigated by X-ray photoelectronspectroscopy, ultraviolet photoelectron spectroscopy, and atomic forcemicroscopy under air exposure. XPS results reveal that 3 h exposureof Li-bis(trifluoromethanesulfonyl)-imide (LiTFSI) dopedspiro-MeOTAD to air results in the migration of LiTFSI from the bottomto the top across the spiro-MeOTAD film. AFM images reveal the presenceof pinholes with an average diameter of ∼135 nm and a densityof ∼3.72 holes/μm2. In addition, cross-sectionalscanning electron microscope images reveal that these pinholes formchannels across the doped spiro-MeOTAD film. Optical microscopy andFourier transform infrared microscopy images confirm the presenceof large pinholes with diameters in the range of 1–20 μmand a density of ∼289 holes/mm2as well. The presenceof pinholes may play a major role in the migration processes of theLiTFSI within the spiro-MeOTAD film as well as on the degradationprocesses of solar cells. This is further confirmed by the rapid decreasingefficiency of perovskite solar cells with solution prepared dopedspiro-MeOTAD layers when exposed to air. [ABSTRACT FROM AUTHOR]

Highlights: [•] Surface cleaning for electrodes with plastic and water-soluble layers. [•] Low work function recovery of ZnO layer by UV-ozone and oxygen plasma treatments. [•] Flexible electrode work function of 3.4–3.6eV with no physical or chemical damage. [•] PEDOT:PSS in multilayer electrode does not diffuse to the upper ZnO layer. [ABSTRACT FROM AUTHOR]

Liquid–liquid equilibrium and tie line data forthe nitricacid/phosphoric acid/water/tri-n-octylamine (TOA)system have been determined at 298.15 K for HNO3mass fractionsof 0.028 to 0.26 and H3PO4mass fractions of0.00 to 0.19. The distribution coefficients of nitric acid (D1) and water (D3) were studied, and the separation factors β(HNO3/H3PO4) was also investigated. The resultsshow that TOA is very selective, since only small quantities of waterand phosphoric acid are present in the organic phase, which indicatesthe good ability of TOA to extract nitric acid from nitric acid/phosphoricacid mixtures. The experimental tie line data were correlated usingthe nonrandom two-liquid (NRTL) model. TOA can be used as an effectiveextractant to separate nitric acid from the HNO3/H3PO4/H2O system. [ABSTRACT FROM AUTHOR]

A series of hybrid heterocyle-containing electron-transportmaterials(ETMs) with different pyridine substitution positions in a singlemolecule were successfully synthesized by regioselective sequentialpalladium-catalyzed Suzuki cross-coupling reactions. B3LYP calculationsshow that the experimental regioselectivity is consistent with thetrends in calculated bond dissociation energies of the carbon–halogen(C–X) bonds of the reactants and intermediates. The two carbonspecies associated with C–N and C–C can be detectedby X-ray photoelectron spectroscopy. Extremely low turn-on voltages(Von) of 2.1 V for electroluminescence,which are readily 0.2–0.3 V lower than the minimum value ofthe emitted photon energy (hv)/e, were experimentally achieved by utilizing the developed ETMs asan electron-transport and hole/exciton-block layer for the classical fac-tris(2-phenylpyridine) iridium (Ir(PPy)3)-basedgreen phosphorescent organic light-emitting devices (OLEDs). In addition,hitherto the lowest operating voltages of 2.39, 2.72, and 3.88 V for100, 1000, and 10 000 cd m–2were achievedwith simultaneously improved external quantum efficiency (ηext) to give a high power efficiency, and the operating voltagefor 100 cd m–2is already corresponding to the valueof hv/e. Atomic force microscopymeasurements reveal morphological fine structure of the thin filmsamples of ETMs with a pyrimidine core, which possibly contributesto the low driving voltages that were achieved for the devices thatare based on these ETMs. These findings indicate that aside from theultralow operating voltage well-balanced carriers can be also achievedwith a finely synthesized hybrid heterocyle-containing ETM as a nondopedelectron-transport layer, and the B3LYP calculation is an effectivemethod to predict the regioselective cross-coupling reactions forfine design of such an ETM. [ABSTRACT FROM AUTHOR]

Reliable measurement of electrical charge transport in molecular layers is a delicate task that requires establishing contacts with electrodes without perturbing the molecular structure of the film. We show how this can be achieved by means of novel device consisting of ultra-flat electrodes separated by insulating material to support the molecular film. We show the fabrication process of these electrodes using a replica technique where gold electrodes are embedded in a silicon oxide film deposited on the angstrom-level flat surface of a silicon wafer. Importantly, the co-planarity of the electrode and oxide areas of the substrate was in the sub-nanometer range. We illustrate the capabilities of the system by mapping the distribution of electrical transport pathways in molecular thin films of self-assembled oligothiophene derivatives using conductive atomic force microscopy. In comparison with traditional bottom contact non-coplanar electrodes, the films deposited on our electrodes exhibited contact resistances lower by a factor of 40 than that of the similar but non-coplanar electrodes. [ABSTRACT FROM AUTHOR]