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The addition of methylammonium chloride (MACl) significantly improves the performance and stability of perovskite fabricated by two-step processes. However, its role in crystallization dynamics has not been thoroughly studied. In this work, a comparison study is carried out using different additions of MACl to investigate the impact of the perovskite crystallization dynamics. In situ grazing incidence wide-angle X-ray scattering (GIWAXS) observations during the annealing process of perovskite revealed that the amount of MACl significantly influences the crystallinity and orientation of the perovskite. Increasing the MACl addition enhances the crystallinity of the perovskite in the wet film's intermediate phase and strengthens the out-of-plane orientation of the FAPbI3 perovskite α-phase (001) planes during annealing. Moreover, it was found that both excessive and insufficient amounts of MACl introduce defects into the perovskite, which are detrimental to device performance. In contrast, an optimal ratio of MACl-9 mg leads to the formation of uniform and large-grained FAPbI3 perovskite films, with the longest carrier lifetimes (163.7 ns) compared to MACl-5 mg (68.4 ns) and MACl- 13 mg (120.1 ns). As a result, the fabricated MACl-9 mg-based solar cell achieved the highest efficiency (22.63%), which is higher than those of MACl-5 mg (21.47%) and MACl-13 mg (20.07%). [ABSTRACT FROM AUTHOR]

Highlights: High-quality large-area perovskite films are prepared using a solid–liquid two-step film formation method combined with CsBr modification for the buried interface and Urea additive for perovskite crystallization. The inverted perovskite solar modules' performance is enhanced to 20.56% in 61.56 cm2 with improved stability. A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid–liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiOx/perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm2 (10 × 10 cm2 substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication. [ABSTRACT FROM AUTHOR]

Perovskite photovoltaics, typically based on a solution-processed perovskite layer with a film thickness of a few hundred nanometres, have emerged as a leading thin-film photovoltaic technology. Nevertheless, many critical issues pose challenges to its commercialization progress, including industrial compatibility, stability, scalability and reliability. A thicker perovskite film on a scale of micrometres could mitigate these issues. However, the efficiencies of thick-film perovskite cells lag behind those with nanometre film thickness. With the mechanism remaining elusive, the community has long been under the impression that the limiting factor lies in the short carrier lifetime as a result of defects. Here, by constructing a perovskite system with extraordinarily long carrier lifetime, we rule out the restrictions of carrier lifetime on the device performance. Through this, we unveil the critical role of the ignored lattice strain in thick films. Our results provide insights into the factors limiting the performance of thick-film perovskite devices. The power conversion efficiencies of thick-film perovskite solar cells lag behind those with nanometre film thickness. Here, the authors rule out the restrictions of carrier lifetime on device performance and reveal the critical role of lattice strain in micron-scale thick perovskite films. [ABSTRACT FROM AUTHOR]

Quasi‐two‐dimensional (quasi‐2D) perovskites are emerging as efficient emitters in blue perovskite light‐emitting diodes (PeLEDs), while the imbalanced crystallization of the halide‐mixed system limits further improvements in device performance. The rapid crystallization caused by Cl doping produces massive defects at the interface, leading to aggravated non‐radiative recombination. Meanwhile, unmanageable perovskite crystallization is prone to facilitate the formation of nonuniform low‐dimensional phases, which results in energy loss during the exciton transfer process. Here, we propose a multifunctional interface engineering for nucleation and phase regulation by incorporating the zwitterionic additive potassium sulfamate into the hole transport layer. By using potassium ions (K+) as heterogeneous nucleation seeds, finely controlled growth of interfacial K+‐guided grains is achieved. The sulfamate ions can simultaneously regulate the phase distribution and passivate defects through coordination interactions with undercoordinated lead atoms. Consequently, such synergistic effect constructs quasi‐2D blue perovskite films with smooth energy landscape and reduced trap states, leading to pure‐blue PeLEDs with a maximum external quantum efficiency (EQE) of 17.32 %, spectrally stable emission at 478 nm and the prolonged operational lifetime. This work provides a unique guide to comprehensively regulate the halide‐mixed blue perovskite crystallization by manipulating the characteristics of grain‐growth substrate. [ABSTRACT FROM AUTHOR]

The deviated crystallization kinetics of solution‐processed perovskite layers caused by the bottom interface is a barrier to comprehensively suppressing the defect formation and further to efficaciously improve the film quality and device performance. Herein, it is reported that the incorporation of a PEA2PbBr4 interlayer can effectively modify the crystallization process of the quasi‐2D mixed‐halide perovskite layers, resulting in enhanced Lewis acid‐base interaction and improved film homogeneity, which contributes to the strong defect passivation efficacy toward efficient sky‐blue emission. As a result, the devices with the bottom‐interface modification show a maximum external quantum efficiency of 14.2%, impressively an outstanding power efficiency of 17.0 lm W−1, and an external quantum efficiency of 12.3% at 1000 cd m−2. This work provides an insight into crystallization kinetics for defect suppression of the perovskite layer and further highlights the defect passivation efficacy of 2D perovskite‐based bottom‐interface modification toward high‐efficiency sky blue‐emitting diodes. [ABSTRACT FROM AUTHOR]

Tin halide perovskite solar cells are promising for the next generation of highly efficient photovoltaics. Their commercialization can be accelerated by increasing their stability in moisture and oxygen. Herein, an n‐type organic molecule (IO‐4Cl) is applied as an interlayer between the perovskite films and electron transport layers in p‐i‐n structured devices. The electron‐rich indacenodithieno‐[3,2‐b]thiophene enhances electron transport, while the hydrocarbon side chains and rigid conjugated backbone isolate air. It is also shown that the C═O in IO‐4Cl can coordinate with Sn2+ on perovskite films' surface and grain boundaries to enhance perovskite crystal stability. In addition, IO‐4Cl slows down crystallization dynamics, resulting in lower non‐radiation recombination. The moisture ingress in the perovskite films is tracked under high relative humidity (RH) and it is found that IO‐4Cl can mitigate moisture infiltration. Finally, the devices with IO‐4Cl maintain 95% of the initial power conversion efficiency after 1200 h of storage in a nitrogen‐filled glovebox, and their stability in ambient air (60–80% RH) is significantly improved against pristine devices, thus demonstrating the beneficial effects of IO‐4Cl interlayer on device stability. [ABSTRACT FROM AUTHOR]

The development of perovskite light‐emitting diodes (PeLEDs) with both high efficiency and excellent stability remains challenging. Herein, a strong correlation between the lattice strain in perovskite films and the stability of resulting PeLEDs is revealed. Based on high‐efficiency PeLEDs, the device lifetime is optimized by rationally tailoring the lattice strain in perovskite films. A PeLED with a high peak external quantum efficiency of 18.2% and a long lifetime of 151 h (T70, under a current density of 20 mA cm−2) is realized with a minimized lattice strain in the perovskite film. In addition, an increase in the lattice strain is found during the long‐time device stability test, indicating that the degradation of the local perovskite lattice structure could be one of the degradation mechanisms for long‐term stable PeLEDs. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials have demonstrated significant potential in various optoelectronic applications, such as photovoltaics, light emitting diodes, photodetectors, and lasers. However, the stability issues of perovskite materials continue to impede their widespread use. Many studies have attempted to understand the complex degradation mechanism and dynamics of these materials. Among them, in situ and/or operando approaches have provided remarkable insights into the degradation process by enabling precise control of degradation parameters and real-time monitoring. In this review, we focus on these studies utilizing in situ and operando approaches and demonstrate how these techniques have contributed to reveal degradation details, including structural, compositional, morphological, and other changes. We explore why these two approaches are necessary in the study of perovskite degradation and how they can be achieved by upgrading the corresponding ex situ techniques. With recent stability improvements of halide perovskite using various methods (compositional engineering, surface engineering, and structural engineering), the degradation of halide perovskite materials is greatly retarded. However, these improvements may turn into new challenges during the investigation into the retarded degradation process. Therefore, we also highlight the importance of enhancing the sensitivity and probing range of current in situ and operando approaches to address this issue. Finally, we identify the challenges and future directions of in situ and operando approaches in the stability research of halide perovskites. We believe that the advancement of in situ and operando techniques will be crucial in supporting the journey toward enhanced perovskite stability. [ABSTRACT FROM AUTHOR]

Highlights: The (011) facet has excellent charge transport properties achieving closer alignment of energy levels. By exploiting the (011) facet a device (0.06 cm2) and a module (29 cm2) achieved power conversion efficiencies of 25.24% and 21.12%, respectively. Perovskite crystal facets greatly impact the performance and stability of their corresponding photovoltaic devices. Compared to the (001) facet, the (011) facet yields better photoelectric properties, including higher conductivity and enhanced charge carrier mobility. Thus, achieving (011) facet-exposed films is a promising way to improve device performance. However, the growth of (011) facets is energetically unfavorable in FAPbI3 perovskites due to the influence of methylammonium chloride additive. Here, 1-butyl-4-methylpyridinium chloride ([4MBP]Cl) was used to expose (011) facets. The [4MBP]+ cation selectively decreases the surface energy of the (011) facet enabling the growth of the (011) plane. The [4MBP]+ cation causes the perovskite nuclei to rotate by 45° such that (011) crystal facets stack along the out-of-plane direction. The (011) facet has excellent charge transport properties and can achieve better-matched energy level alignment. In addition, [4MBP]Cl increases the activation energy barrier for ion migration, suppressing decomposition of the perovskite. As a result, a small-size device (0.06 cm2) and a module (29.0 cm2) based on exposure of the (011) facet achieved power conversion efficiencies of 25.24% and 21.12%, respectively. [ABSTRACT FROM AUTHOR]

Organic–inorganic perovskite solar cells (PSCs) have achieved great attention due to their expressive power conversion efficiency (PCE) up to 25.7%. To improve the photovoltaic performance of PSCs, interface engineering between the perovskite and hole transport layer (HTL) is a widely used strategy. Following this concept, benzyl trimethyl ammonium chlorides (BTACls) are used to modify the wet chemical processed perovskite film in this work. The BTACl‐induced low dimensional perovskite is found to have a bilayer structure, which efficiently decreases the trap density and improves the energy level alignment at the perovskite/HTL interface. As a result, the BTACl‐modified PSCs show an improved PCE compared to the control devices. From device modeling, the reduced charge carrier recombination and promoted charge carrier transfer at the perovskite/HTL interface are the cause of the open‐circuit (Voc) and fill factor (FF) improvement, respectively. This study gives a deep understanding for surface modification of perovskite films from a perspective of the morphology and the function of enhancing photovoltaic performance. [ABSTRACT FROM AUTHOR]

Metal halide perovskite solar cells may work for application in extreme temperatures, such as those experienced under extraterrestrial conditions. However, device performances in extreme temperatures are poorly investigated. This work systematically explores the performance of perovskite solar cells between −160 and 150 °C. In situ grazing‐incidence wide‐angle X‐ray scattering discloses perovskite phase transition and crystal disordering as dominant factors for the temperature‐dependent device efficiency deterioration. It is shown that perovskite lattice strain and relaxation originating from extreme temperature variations are recoverable, and so are the perovskite structure and photovoltaic performances. This work provides insights into the functioning under extreme temperatures, clarifying bottlenecks to overcome and the potential for extraterrestrial applications. [ABSTRACT FROM AUTHOR]

The relatively lower crystallinity and random orientation of quantum well structures hinder carrier transport and limit the performance of formamidinium (FA) based low‐n 2D perovskite devices. In this work, the crystallization and quantum well orientation are fine tuned to achieve efficient low‐n FA based Ruddlesden–Popper perovskite solar cells. The effects of different ionic additives on the crystallization, orientation, and photovoltaic performance of FA based low‐n 2D perovskites are comparatively investigated. It is found that NH4+ and SCN− can significantly retard the heterogeneous crystallization of low‐n phases in the intermediate state, and drive the templated growth of quantum well structure with vertical orientation. The optimized photovoltaic device based on (BA)2(FA)3Pb4I13 achieved a power conversion efficiency (PCE) of 18.14%, setting the highest record for FA‐based low‐n 2D perovskite solar cells as far as it is known (average n = 4). The unencapsulated device exhibited excellent stability and maintained 93.3% of its original PCE at 85 °C, and 86.3% at 1 Sun illumination after 720 h in humid ambient condition. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting didoes (PeLEDs) have shown considerable potential in solution‐processable display applications. However, the performance of blue PeLEDs in terms of efficiency and stability hinders their practicality on account of severe trap‐mediated nonradiative recombination losses and halide phase segregation. To ameliorate these issues, mixed‐halide sky‐blue perovskite materials are strategically modulated through crystal defect passivation with a trifurcate isocyanate oligomer, which leads to the synergistical suppression of charge trap density and halide ion migration. The proposed approach enables the performance improvement for sky‐blue PeLEDs, exhibiting a peak external quantum efficiency of 14.82% and spectrally stable emission at 487 nm. In addition, prolonged operational lifetime and enhanced capability of moisture resistance are achieved simultaneously, approaching a half‐lifetime of ≈2900 s at an initial brightness of 178 cd m–2. [ABSTRACT FROM AUTHOR]

2D perovskites possess superior humidity stability but inferior power conversion efficiency (PCE) compared with 3D perovskites due to their typically insulating spacers. Size of the spacer cation is determinative for the formation of 2D perovskite, and fullerene is believed not to be capable of templating 2D perovskite structure because of its larger size than the width of the lead‐halide octahedron despite its well‐known strong electron‐accepting ability. Herein, a novel amino‐functionalized fullerene derivative (abbreviated as C60‐BPAM) is developed and an 'improbable' spacer for 2D/3D hybrid perovskite solar cells (PSCs), achieving enhanced electron transport is applied. Unlike most of the reported alkylammonium spacers that are based on insulating organic tails, the incorporation of a highly conductive fullerene tail within C60‐BPAM2+ leads to increased electron density in 2D/3D perovskite and induces an additional built‐in electric field, facilitating electron transport in PSCs. Besides, the 2D/3D hybrid structure helps to passivate both of the shallow‐ and deep‐level defects within perovskite. As a result, the PCE of 2D/3D PSCs improves from 19.36% (3D MAPbI3 PSCs) to 20.21%. Moreover, the 2D/3D PSCs show significant improvement in the humidity stability compared to the 3D counterparts. [ABSTRACT FROM AUTHOR]

Quasi‐2D metal halide perovskite light emitting diodes (PeLEDs) have attracted a lot of attentions in recent years, while their potential applications in displays and lighting are limited by the device stability. Although defect passivation in PeLEDs is an effective method to ameliorate the unstable problem, the underlying mechanisms need to be further explored. Herein, organic spacer cations with different charge distributions and formation energies in quasi‐2D CsPbBr3 perovskites are utilized to unravel the defect passivation mechanisms, including phenylmethanamine, 2‐phenylethanamine bromide, and 4‐phenylbutylammonium. The experimental findings and density functional theory calculation reveal that the defect passivation occurs by the electrostatic interaction between defective PbBr64− octahedrons and proper organic spacer cations during the annealing process, particularly at the grain boundaries. The thermal stability of the perovskite films and device performance are improved after the effective defect passivation process. The exploration of the defect passivation process in perovskites will be beneficial to the development of high‐performance PeLEDs. [ABSTRACT FROM AUTHOR]

While there is promising achievement in terms of the power conversion efficiency (PCE) of perovskite solar cells (PSCs), long‐term stability has been considered the main obstacle for their practical application. In this work, the authors demonstrate the small monomer 2‐(dimethylamino) ethyl methacrylate (DMAEMA) with unsaturated carboxylic acid ester bond in the antisolvent for perovskite formation to improve the PCE and stability. The results show that DMAEMA is self‐polymerized and uniformly distributed in the film, contributing to the improved crystallinity of the perovskites. Equally important, it is found that there are newly established interactions of Pb2+ and DMAEMA, and iodine and ternary amine between DMAEMA and perovskites, which improves the uniformity of the lead (II) iodide vertical distribution along with the films and thus phase stability, as well as largely decreases defects density in the film. Overall, the inverted PSCs with DMAEMA exhibit a open‐circuit voltage of 1.10 V, short‐circuit current of 23.86 mA cm−2, fill factor of 0.82, and finally PCE reaches 21.52%. Meanwhile, the PSC stability is significantly improved due to the inhibition of the formation of iodine, reduction of the uncoordinated Pb2+, and suppression of phase segregation. [ABSTRACT FROM AUTHOR]

2D/3D mixed tin (Sn)‐based perovskites serving as excellent active layers possess a potential for enhancing film/device stabilities, open‐circuit voltage, and power conversion efficiency (PCE) of perovskite solar cells (PSCs). Unfortunately, the poor morphology and low film coverage of these 2D/3D perovskites jeopardize their device performance and stability. Herein, doping of hydroxyl‐rich d‐sorbitol into hole transport layer poly(3,4‐ethenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) can effectively address the PEDOT:PSS/perovskite interfacial issues. The multihydroxyl groups from d‐sorbitol can sufficiently anchor iodide ions ([SnI6]4− or free I−) of PEA0.1(FA0.75MA0.25)0.9SnI3 perovskite via hydrogen bond, which not only introduces more nucleation sites with improved crystallinity along the preferential crystal orientations, but also reduces the trap states' density and suppresses the iodide ions' migration. In the meanwhile, the content of SnI2 is reduced in the resulting perovskite films. All of these are conducive to form compact and smooth high‐quality perovskite films with less traps and enhanced stability. Benefitting from these, an inverted PSC with a champion PCE of 10.46% and a lifetime of 700 h (25% attenuation in N2) is eventually achieved. This work provides a promising approach to manufacture highly efficient and stable Sn‐based PSCs based on 2D/3D mixed perovskites. [ABSTRACT FROM AUTHOR]

Regardless of the rapid advance on perovskite light‐emitting diodes (PeLEDs), the lack of long‐term operational stability hinders the practicality of this technology. Particularly, thermal management is indispensable to control the Joule heating induced by charge transport and parasitic re‐absorption of internally confined photons. Herein, a synergetic device architecture is proposed for minimizing the optical energy losses in PeLEDs toward high efficiency and long lifetime. By adopting a carefully modified perovskite emitter in combination with an improved light outcoupling structure, red PeLEDs emitting at 666 nm achieve a peak external quantum efficiency of 21.2% and an operational half‐lifetime of 4806.7 h for an initial luminance of 100 cd m‐2. The enhanced light extraction from trapped modes can efficiently reduce the driving current and suppress optical energy losses in PeLEDs, which in turn ameliorate the heat‐induced device degradation during operation. This work paves the way toward high‐performance PeLEDs for display and lighting applications in the future. [ABSTRACT FROM AUTHOR]

Efficient and stable blue emission of perovskite light‐emitting diodes (PeLEDs) is a requisite toward their potential applications in full‐color displays and solid‐state lighting. Rational manipulation over the entire electroluminescence process is promising to break the efficiency limit of blue PeLEDs. Herein, a facile device architecture is proposed to achieve efficient blue PeLEDs for simultaneously reducing the energetic loss during electron‐photon conversion and boosting the light outcoupling. Effective interfacial engineering is employed to manipulate the perovskite crystallization nucleation, enabling highly compact perovskite nanocrystal assemblies and suppressing the trap‐induced carrier losses by means of interfacial hydrogen bonding interactions. This strategy contributes to a high external quantum efficiency (EQE) of 12.8% for blue PeLEDs emitting at 486 nm as well as improved operational stability. Moreover, blue PeLEDs reach a peak EQE of 16.8% with the incorporation of internal outcoupling structures for waveguided light, which can be further raised to 27.5% by integrating a lens‐based structure for substrate‐mode light. These results verify the validity of this strategy in producing efficient and stable blue PeLEDs for practical applications. [ABSTRACT FROM AUTHOR]

While tremendous progress has recently been made in perovskite light‐emitting diodes (PeLEDs), large‐area blue devices feature inferior performance due to uneven morphologies and vast defects in the solution‐processed perovskite films. To alleviate these issues, a facile and reliable interface engineering scheme is reported for manipulating the crystallization of perovskite films enabled by a multifunctional molecule 2‐amino‐1,3‐propanediol (APDO)‐triggered "anchoring effect" at the grain‐growth interface. Sky‐blue perovskite films with large‐area uniformity and low trap states are obtained, showing the distinctly improved radiative recombination and hole‐transport capability. Based on the APDO‐induced interface engineering, synergistical boost in device performance is achieved for large‐area sky‐blue PeLED (measuring at 100 mm2) with a peak external quantum efficiency (EQE) of 9.2% and a highly prolonged operational lifetime. A decent EQE up to 6.1% is demonstrated for the largest sky‐blue device emitting at 400 mm2. [ABSTRACT FROM AUTHOR]

Inkjet printing is a powerful technology for realizing high‐density pixelated perovskite light‐emitting diodes (PeLEDs). However, the coffee‐stain effect in the inkjet printing process often leads to uneven thickness and poor crystallization of printed perovskite features, which deteriorates the performance of PeLEDs. Here, a strategy is developed to suppress the coffee‐stain effect via enhancing Marangoni flow strength. An interfacial poly(vinylpyrrolidone) (PVP) layer is incorporated to tune the surface tension of the underlying hole transport layer (HTL) and enhance the perovskite crystallization. The substrate temperature is also carefully controlled to tune the printing solvent evaporation rate rationally. By optimizing the thickness of the PVP layer and the temperature of the printing stage, the coffee‐stain effect is dramatically restrained. In addition, the interfacial insulating PVP layers play a positive role in suppressing leakage current level of PeLEDs by avoiding any direct electrical contact between HTL and electron transporting layer. Finally, an inkjet‐printed PeLED with a brightness of 3640 cd m–2 and external quantum efficiency of 9.0% is achieved. This work highlights the availability of inkjet‐printing technology for fabricating patterned PeLEDs in information display applications. [ABSTRACT FROM AUTHOR]

Tin halide perovskites attract incremental attention to deliver lead‐free perovskite solar cells. Nevertheless, disordered crystal growth and low defect formation energy, related to Sn(II) oxidation to Sn(IV), limit the efficiency and stability of solar cells. Engineering the processing from perovskite precursor solution preparation to film crystallization is crucial to tackle these issues and enable the full photovoltaic potential of tin halide perovskites. Herein, the ionic liquid n‐butylammonium acetate (BAAc) is used to tune the tin coordination with specific O...Sn chelating bonds and NH...X hydrogen bonds. The coordination between BAAc and tin enables modulation of the crystallization of the perovskite in a thin film. The resulting BAAc‐containing perovskite films are more compact and have a preferential crystal orientation. Moreover, a lower amount of Sn(IV) and related chemical defects are found for the BAAc‐containing perovskites. Tin halide perovskite solar cells processed with BAAc show a power conversion efficiency of over 10%. This value is retained after storing the devices for over 1000 h in nitrogen. This work paves the way toward a more controlled tin‐based perovskite crystallization for stable and efficient lead‐free perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

The crystallization mechanism of the perovskite crystals inside the mesopores of printable mesoscopic perovskite solar cells is demonstrated by in situ grazing-incidence X-ray diffraction. Ionic liquids can universally tune the crystallization process of different perovksites in the mesopores regradless of the precursor solvents, resulting in enhanced efficiency. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) are emerging candidates for the applications of solution‐processed full‐color displays. However, the device performance of deep‐blue PeLED still lags far behind that of their red and green counterparts, which is largely limited by low external quantum efficiency (EQE) and poor operational stability. Here, a facile and reliable crystallization strategy for perovskite grains is proposed, with improved deep‐blue emission through rational interfacial engineering. By modifying the substrate with potassium cation (K+) as the supplier of heterogeneous nucleation seeds, the interfacial K+‐guided grain growth is realized for well‐packed perovskite assemblies with high surface coverage and the controlled crystal orientation, leading to the enhanced radiative recombination and hole‐transport capabilities. Synergistical boost in device performance is achieved for deep‐blue PeLEDs emitting at 469 nm with a peak EQE of 4.14%, a maximum luminance of 451 cd m–2, and spectrally stable color coordinates of (0.125, 0.076) that matches well with the National Television System Committee (NTSC) standard blue. [ABSTRACT FROM AUTHOR]

Interfacial engineering is essential for facilitating carrier separation, charge extraction, and enhancing the stability in organic–inorganic perovskite solar cells (PSCs). Herein, a facile and effective method is demonstrated not only to tune the electronic performance of electron transporting layer (ETL) but also to passivate the defects at the interface between the ETL and perovskite. On the top of the tin(IV) oxide (SnO2) ETL, butylammonium chloride (BACl) and lead(II) iodide (PbI2) are introduced as interface to modify the ETL/perovskite interface. The PSCs with interface modified exhibit a power conversion efficiency (PCE) of 21.15%, compared to 18.33% for the device without interface modified. Such enhancement in efficiency is mainly attributed to a better energy band alignment, and the quality of perovskite films is improved through the interface modification, thus enhancing photogenerated charge extraction and leading to low charge carrier recombination at the interface of ETL/perovskite. Furthermore, the device with interface modified exhibits significant stability. This work provides an alternative strategy on the ETL/perovskite interface to obtain highly stable and efficient PSCs. [ABSTRACT FROM AUTHOR]

All‐inorganic lead halide perovskites are promising candidates for optoelectronic applications. However, fundamental questions remain over the component interaction in the perovskite precursor solution due to the limitation of the most commonly used solvents of N,N‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Here, we report an interaction tailoring strategy for all‐inorganic CsPbI3−xBrx perovskites by involving the ionic liquid solvent methylammonium acetate (MAAc). C=O shows strong interaction with lead (Pb2+) and N−H⋅⋅⋅I hydrogen bond formation is observed. The interactions stabilize the perovskite precursor solution and allow production of the high‐quality perovskite films by retarding the crystallization. Without the necessity for antisolvent treatment, the one‐step air‐processing approach delivers photovoltaic cells regardless of humidity, with a high efficiency of 17.10 % along with long operation stability over 1500 h under continuous light illumination. [ABSTRACT FROM AUTHOR]

Here, we report the electronic structures at the N, N′-dipentyl-3,4,9,10-perylenedicarboximide (PTCDI-C5)/CH3NH3PbI3 interface identified in-situ by X-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. Strong chemical reactions are found to occur upon the deposition of PTCDI-C5 molecules on CH3NH3PbI3. Electron donation from PTCDI-C5 molecules to CH3NH3PbI3 leads to the filling of surface states and the emergence of an interfacial gap state with its onset tailed to the Fermi level. As a consequence, the downward surface band bending resulting from surface states acting as donor states at the pristine perovskite surface is reduced by 0.2 eV. After the energy level alignment at the interface is established, the perovskite conduction band minimum is found to be in line with the lowest unoccupied molecular orbital favoring the electron extraction with a moderate valence band maximum-highest occupied molecular orbital offset of ∼0.7 eV. The present results demonstrate that interfacial chemical reactions can dictate energetics at organic/perovskite interfaces. Understanding the chemical interaction and resultant electronic structures at those interfaces is crucial for efficient and long-term stable perovskite-based devices when passivation of chemical active sites and matched energy level could be readily reached. [ABSTRACT FROM AUTHOR]

Abstract: In this contribution, a facile and universal method is successfully reported to fabricate perovskite solar cells (PSCs) with enhanced efficiency and stability. Through dissolving functional conjugated polymers in antisolvent chlorobenzene to treat the spinning CH3NH3PbI3 perovskite film, the resultant devices exhibit significantly enhanced efficiency and longevity simultaneously. In‐depth characterizations demonstrate that thin polymer layer well covers the top surface of perovskite film, resulting in certain surface passivation and morphology modification. More importantly, it is shown that through rational chemical modification, namely molecular fluorination, the air stability and photostability of the perovskite solar cells are remarkably enhanced. Considering the vast selection of conjugated polymer materials and easy functional design, promising new results are expected in further enhancement of device performance. It is believed that the findings provide exciting insights into the role of conjugated polymer in improving the current perovskite‐based solar cells. [ABSTRACT FROM AUTHOR]

We systematically investigated the impact of stoichiometric ratio variation between PbX2 and AX on hybrid perovskite films from the perspective of microstructure, especially on the plane stacking directions, using the two-dimensional synchrotron radiation grazing incidence wide-angle X-ray scattering (GIWAXS) technique. The tuned crystal plane stacking in perovskite films can consequently enlighten further explorations about the relationship between microstructure and solar cell performance. [ABSTRACT FROM AUTHOR]

Influence of K/ Na ratio in ( K x Na1− x) NbO3 on the ferroelectric stability and consequent changes in the electrical properties of 0.99( Bi0.5 Na0.4 K0.1) TiO3-0.01( K x Na1− x) NbO3 ( BNKT- K x NN) ceramics were investigated. Results showed that change of K/ Na ratio in KNN induces a phase transition from ferroelectric to ergodic relaxor phase with a significant disruption of the long-range ferroelectric order, and correspondingly adjusts the ferroelectric-relaxor transition point TF−R to room temperature. Accordingly, giant strain of ~0.46% (corresponding to a large signal d33* of ~575 pm/V) which is comparable to that of Pb-based antiferroelectrics is obtained at a K/ Na ratio of ~1, and the emergence of large strain response induced by the change of K/ Na ratio of KNN can be well explained by the correlation between the position of ferroelectric-ergodic relaxor phase boundary in the BNKT-K x NN system and the tolerance factor t of the end number ( K x NN). In situ high-energy X-ray scattering experiments with external field reveals that the large strain response in the studied system is likely related to the electric field-induced distortion from the pseudocubic structure. [ABSTRACT FROM AUTHOR]

Blending perovskite with different cations has been successful in improving performance of perovskite solar cells, but the complex pathway of perovskite crystal formation remains a mystery, hindering its further development. In this paper, the detailed crystallization process of formamidinium lead iodide (FAPbI3) perovskite films doped by methylammonium lead bromide (MAPbBr3) additive was investigated by in situ grazing incident wide-angle X-ray scattering measurements during both spin coating and annealing. During spin-coating, it was found that the FAPbI3 perovskite precursor easily formed a mixture of black perovskite phase (α phase) and non-perovskite yellow phase (δ phase) after the addition of MAPbBr3, whereas only δ phase formed without MAPbBr3. The δ phase gradually converted to α phase during annealing and there was only α phase left in both films with and without MAPbBr3. However, the doped films presented high film quality without PbI2 residue in contrast to the undoped films. These findings imply that the MAPbBr3 additive can effectively suppress the formation of the unfavorable δ phase and trigger the formation of the optically active α phase even during spin-coating, which enhances the film quality possibly by removing the energy barriers from δ phase to α phase at room temperature. Finally, PSCs based on MAPbBr3-doped FAPbI3 were fabricated with a champion efficiency as high as 19.4% from 14.2% for the PSCs based on undoped FAPbI3. [ABSTRACT FROM AUTHOR]

Phase segregation can bring low crystallinity and orientation, giving rise to poor carrier transport and high defect density, leading to poor device performance. In order to reduce oxidation and defect density and regulate film growth, lots of reductive additives such as SnF2 are explored as additives in tin perovskite film growth. Despite the oxidation is effectively reduced, it induces phase segregation. Herein, a reductive molecule NH5F2 with a bi‐fluoride anion is explored to address this challenge for tin perovskite solar cells. This bi‐fluoride anion reduces coordination energy with Sn2+ compared to SnF2, hence the byproduct of [F─H─F]− can be eliminated during the film annealing process, effectively preventing fluoride segregation. As a result, a highly oriented perovskite film with reduced oxidation is fabricated. The film shows reduced defect density and carrier recombination, leading to improved current density. Consequently, a tin‐based perovskite solar cell with an efficiency of 15.04% is fabricated, ranking as one of the highest efficiencies reported up to now. [ABSTRACT FROM AUTHOR]

Two‐step sequential deposition of perovskite films is proven efficient and compatible with large‐scale production. Nevertheless, its critically regulated environmental humidity often remains a burden, hindering its applications in reproducible fabrication of perovskite solar cells (PSCs). Herein, by introducing a water ethyl acetate (W‐EA) solution treatment before annealing, improved perovskite crystallinity and homogeneity in FA0.95‐xMAxCs0.05PbI3 films without additional composition regulation is achieved. In situ Grazing‐incidence Wide‐angle X‐ray Scattering experiments highlighted accelerated crystallization kinetics in W‐EA‐treated films, leading to high‐quality perovskite formation. PSCs based on this method reached an optimal power conversion efficiency of 25.01% and demonstrated enhanced moisture resistance, retaining 88% efficiency after 1000 h in ambient conditions. This W‐EA treatment simplifies the fabrication process, greatly reducing the need for controlled humidity, and offers insights into the role of water in perovskite film crystallization, with significant implications to produce high‐performance PSCs. [ABSTRACT FROM AUTHOR]

Deep-Blue Emission: Interfacial Potassium-Guided Grain Growth for Efficient Deep-Blue Perovskite Light-Emitting Diodes (Adv. Funct. Keywords: crystallization manipulation; deep-blue emission; interface engineering; perovskite light-emitting diodes EN crystallization manipulation deep-blue emission interface engineering perovskite light-emitting diodes 1 1 1 02/05/21 20210203 NES 210203 In article number 2006736, Yan-Qing Li, Jian-Xin Tang, and co-workers demonstrate a facile and reliable crystallization strategy for interfacial potassium-guided perovskite grain growth, leading to efficient deep-blue light-emitting diodes with an external quantum efficiency of 4.14% and stable color coordinates of (0.125, 0.076). Crystallization manipulation, deep-blue emission, interface engineering, perovskite light-emitting diodes. [Extracted from the article]

Dion–Jacobson (DJ) phase halide perovskites have attracted extensive attention in photovoltaic devices due to their significantly enhanced stability when compared with conventional 3D analogs. However, fundamental questions concerning the quantum well (QW) barrier thicknesses, which are critical to design efficient DJ phase perovskite photovoltaics, remain unknown. Herein, it is unambiguously demonstrated that QW barrier thickness, depending on bulky organic ammonium spacers with different chain lengths, such as 1.3‐propanediamine (PDA), 1.4‐butanediamine (BDA), 1.5‐pentamethylenediamine (PeDA), and 1.6‐hexamethylenediamine (HDA), allows the control of orientation and QW distribution. The DJ phase perovskites based on PDA and BDA have suitable QW barrier thicknesses, which exhibit excellent orientation and more uniform QW distribution, allowing a smooth bandgap transition that leads to longer carrier diffusion length, higher charge mobility, and lower defect density. Conversely, PeDA and HDA, with thicker QW barriers, result in lower orientation and multiple DJ perovskite phases. DJ phase perovskite photovoltaic devices based on PDA and BDA show significantly improved power conversion efficiencies (PCEs) of 14.16% and 16.38% compared with PCEs of 12.95% and 10.55% for PeDA and HDA analogs, respectively. [ABSTRACT FROM AUTHOR]

Although all‐inorganic perovskite solar cells (PSCs) demonstrate high thermal stability, cesium‐lead halide perovskites with high iodine content suffer from poor stability of the black phase (α‐phase). In this study, it is demonstrated that incorporating InCl3 into the host perovskite lattice helps to inhibit the formation of yellow phase (δ‐phase) perovskite and thereby enhances the long‐term ambient stability. The enhanced stability is achieved by a strategy for the structural reconstruction of CsPbI2Br perovskite by means of In3+ and Cl− codoping, which gives rise to a significant improvement in the overall spatial symmetry with a closely packed atom arrangement due to the crystal structure transformation from orthorhombic (Pnma) to cubic (Pm‐3m). In addition, a novel thermal radiation heating method that further improves the uniformity of the perovskite thin films is presented. This approach enables the construction of all‐inorganic InCl3:CsPbI2Br PSCs with a champion power conversion efficiency of 13.74% for a small‐area device (0.09 cm2) and 11.4% for a large‐area device (1.00 cm2). Incorporation of indium(III) chloride is directly shown to induce the structural reconstruction of CsPbI2Br perovskite at the microscopic level, which allows the stabilization of the α‐phase perovskite by means of increasing the structure tolerance factor and decreasing the grain size. Consequently, the square‐centimeter all‐inorganic InCl3:CsPbI2Br perovskite solar cells yield a power conversion efficiency of 11.4% with high stability. [ABSTRACT FROM AUTHOR]

Quasi‐2D Ruddlesden–Popper (RP) perovskites with quantum‐size‐tuned nanoplatelet crystallites are particularly attractive for light‐emitting diode (LED) applications because of their excellent charge transport, bandgap tunability, and narrow emission peaks. Favorable energy cascade structure in 2D RP perovskites can funnel the photoexcitation from large‐bandgap nanoplatelets to the lowest bandgap ones, which promises efficient radiative recombination. However, how to rationally control the nanoplatelet distribution as well as the crystallization characteristics to ensure efficient energy transfer and charge transport in perovskite films is still challenging. Here, a simple path to facilely tune the nanoplatelet distribution as well as the crystal orientation via carefully controlling postannealing condition is provided. With optimizing the thermal annealing time, compact and flat perovskite films with high photoluminescence quantum yield are obtained. Based on the optimized perovskite films, green LED with a current efficiency of 43.7 cd A−1, corresponding to an external quantum efficiency of 13.9%, is achieved. This work provides a simple path to target highly efficient perovskite LED devices. Efficient perovskite light‐emitting diodes (LEDs) are achieved via tuning nanoplatelet distribution and the crystallinity orientation of quasi‐2D perovskite films. By using the optimized perovskite film to build LED devices, a current efficiency of 43.7 cd A−1 and an external quantum efficiency of 13.9% are achieved, which are the one of the impressive performances in this field. [ABSTRACT FROM AUTHOR]

Daily temperature variations induce phase transitions and lattice strains in halide perovskites, challenging their stability in solar cells. We stabilized the perovskite black phase and improved solar cell performance using the ordered dipolar structure of b-poly(1,1-difluoroethylene) to control perovskite film crystallization and energy alignment. We demonstrated p-i-n perovskite solar cells with a record power conversion efficiency of 24.6% over 18 square millimeters and 23.1% over 1 square centimeter, which retained 96 and 88% of the efficiency after 1000 hours of 1-sun maximum power point tracking at 25° and 75°C, respectively. Devices under rapid thermal cycling between −60° and +80°C showed no sign of fatigue, demonstrating the impact of the ordered dipolar structure on the operational stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wide-bandgap polymers in organic photovoltaics provide a valuable toolbox for developing hole transport materials (HTMs). • Perovskite solar cells (PSCs) using dopant-free PBQx-TCl HTM demonstrated an efficiency of 24.12 % with a high V OC of 1.20 V and good operational stability (T 90 > 600 hours). Dopant-free polymer hole transport materials (HTMs) exhibit high thermal stability, hydrophobicity and film-processing capabilities, demonstrating excellent device efficiency and stability in perovskite solar cells (PSCs). Continued innovation of wide-bandgap polymers in organic photovoltaics (OPV) provides a valuable toolbox for developing polymeric HTMs. Here, we propose an effective molecule design for selecting structurally relevant polymers (D18, D18-Cl, PBQx-TCl) available for commercialization. We discover that the highly planar conjugated backbones play a crucial role in regulating the packing orientation of the film relative to the perovskite. The moderate aggregation with face-on packing orientation is conducive to the high-quality film, which is responsible for better contact with perovskite and superior charge extraction and transport. Simultaneously, these polymers with robust passivation enhanced the open circuit voltage (V OC) without additional passivation layers, streamlining the device process. Consequently, a PSC using dopant-free PBQx-TCl HTL demonstrated an efficiency of 24.12 % with a high V OC of 1.20 V and good operational stability (T 90 > 600 h). This work reveals transparent structure–function-performance relationships between molecules and devices, paving the way for the subsequent development of high-performance HTMs. [ABSTRACT FROM AUTHOR]

Anti-solvent washing has been widely used in preparation of compact and uniform perovskite films. However, it often brings more surface defects in the prepared film. Additive PTB7 in anti-solvent is proven to significantly enhance perovskite crystallinity on the film surface. Finally, a champion power-conversion efficiency of 21.41% was achieved in PTB7-washed PSCs which retained over 90% of the initial PCE after 350 h using maximum power point tracking without being encapsulated. [Display omitted] • PTB7 significantly enhance perovskite film surface crystallinity, as evidenced by depth sensitive grazing incidence X-ray diffraction. • PTB7 molecules tend to interact with Pb atoms which slows down crystallization dynamics in the surface region for enhanced perovskite crystallinity and effectively passivates defects at perovskite grain boundary and film surface. • The alkyl chains in PTB7 were shown to improve film surface hydrophobicity. • The champion device obtained an elevated efficiency of 21.41% and improved stability. Low temperature solution-processed organic–inorganic hybrid perovskite films inevitably encounter defects especially on surface and at grain boundaries. Anti-solvent washing has been widely practiced in fabricating uniform and dense perovskite films, but unfortunately it could cause even more defects on surface. Herein, polymer PTB7 was introduced into anti-solvent as an additive to significantly enhance perovskite film surface crystallinity with fewer defects, as evidenced by depth sensitive grazing incidence X-ray diffraction. Such improvements could be attributed to the Lewis base coordination bonds formed between PTB7 and Pb atoms in the surface region which slow down crystallization dynamics for enhanced perovskite surface crystallinity and effectively passivate defects at the perovskite grain boundary and film surface. With PTB7 in anti-solvent, the fabricated perovskite solar cells (PSCs) achieved a champion power conversion efficiency (PCE) of 21.41% from that of 19.79% for the control devices without PTB7. In addition, the hydrophobic alkyl chains in PTB7 were shown to improve film surface hydrophobicity with enhanced environmental stability of both the fabricated films and PSCs. Thus, addition of PTB7 in anti-solvent is proven to effectively improve the performance and stability of PSCs which could be easily applied in the fabrication of PSCs and other perovskite-based optoelectronics. [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]

Indoor photovoltaics (IPVs) are favored for their speciality to provide sustainable and reliable energy for low-power electronic devices. As an ideal IPVs material, perovskite has been well explored in recent years. Herein, we focus on enhancing the photoelectric properties of the perovskite crystal under low light. By introducing N , N ′-bis(dimethylaminopropyl- N ‴-oxide)-perylene-3,4,9,10-tetracarboxidiimide (PDINO) into the perovskite, the crystallinity degree of the perovskite films are proven to be improved by synchrotron-based grazing incidence X-ray diffraction, thereby effectively enhancing the exciton transmission and separation in the perovskite. By using ultrafast spectroscopy, the influence of the optimized charge separation inside the perovskite under low light has been systematically analyzed. The final optimal perovskite solar cell showed an impressive indoor power conversion efficiency (PCE) of 37.9% under 1000 lux low light, and a PCE of 21.3% under 1 sun illumination. These findings proved doping of the perovskite by strong electron acceptors as a valid strategy for efficient charge transport, paving the way to their applications as IPVs. • The PDINO molecules can optimize the perovskite crystals formation and effectively reduce the defects in the film. • Analyzing tDOS and ultrafast spectroscopy, the defects passivation and the optimization of exciton separation were revealed. • A ∼37.9% efficient (1000 lux) indoor PSC is obtained based on PDINO-based device. [ABSTRACT FROM AUTHOR]

[Display omitted] • MoO 3 dope PTAA to lower its HOMO aligning better with MAPbI 3 VBM. • The hole transport and the interfacial hole extraction are enhanced. • The fabricated inverted planar PSCs achieve a champion PCE of 20.06%. The hole transport layer (HTL) plays a key role in determining the performance of planar perovskite solar cells (PSCs). Poly[bis(4-phenyl)(2,4, 6-triMethylphenyl)aMine] (PTAA), a polymer with good stability, is one of the promising HTL candidates for PSCs. However, notable interfacial carrier recombination limits the performance of PSCs based on PTAA HTL, due to the large gap between the highest-occupied molecular orbital (HOMO) of PTAA and the valance band maximum (VBM) of MAPbI 3 perovskite as well as the low intrinsic hole mobility of PTAA. Herein, PTAA was doped by 3 wt% of molybdenum oxide (MoO 3) to move down its HOMO by 0.16 eV, leading to a better matching with the MAPbI 3 perovskite. Meanwhile, the MoO 3 dopant was demonstrated to improve the hole transport in PTAA and hole extraction at the PTAA/perovskite interface. Eventually, the fabricated inverted planar PSCs using PTAA HTL with 3 wt% MoO 3 achieved the PCE of 20.06% as compared to that of 17.71% by using pristine PTAA HTL. The present work thus proposes a simple approach to utilize MoO 3 as a dopant to substantially improve the molecular HTLs for high-performance PSCs and other perovskite-based optoelectronics. [ABSTRACT FROM AUTHOR]