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The vacancy-ordered quadruple perovskite Cs4CdBi2Cl12, as a newly-emerging lead-free perovskite system, has attracted great research interest due to its excellent stability and direct band gap. However, the poor luminescence performance limits its application in light-emitting diodes (LEDs) and other fields. Herein, for the first time, an Ag+ ion doping strategy was proposed to greatly improve the emission performance of Cs4CdBi2Cl12 synthesized by hydrothermal method. Density functional theory calculations combined with experimental results evidence that the weak orange emission from Cs4CdBi2Cl12 is attributed to the phonon scattering and energy level crossing due to the large lattice distortion under excited states. Fortunately, Ag+ ion doping breaks the intrinsic crystal field environment of Cs4CdBi2Cl12, suppresses the crossover between ground and excited states, and reduces the energy loss in the form of nonradiative recombination. At a critical doping amount of 0.8%, the emission intensity of Cs4CdBi2Cl12:Ag+ reaches the maximum, about eight times that of the pristine sample. Moreover, the doped Cs4CdBi2Cl12 still maintains excellent stability against heat, ultraviolet irradiation, and environmental oxygen/moisture. The above advantages make it possible for this material to be used as solid-state phosphors for white LEDs applications, and the Commission International de l'Eclairage color coordinates of (0.31, 0.34) and high color rendering index of 90.6 were achieved. More importantly, the white LED demonstrates remarkable operation stability in air ambient, showing almost no emission decay after a long working time for 48 h. We believe that this study puts forward an effective ion-doping strategy for emission enhancement of vacancy-ordered quadruple perovskite Cs4CdBi2Cl12, highlighting its great potential as efficient emitter compatible for practical applications. [ABSTRACT FROM AUTHOR]

The rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin‐film semiconductors has triggered interest in their use for direct solar‐driven water splitting to produce hydrogen. However, application of these low‐cost, electronic‐structure‐tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic‐catalyst‐electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n+silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high‐temperature annealing of the catalyst/TiO2‐protected‐n+silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA1‐xCsx)PbI3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro‐OMeTAD‐hole‐transport‐layer (HTL)‐based HOIP/n+Si solar cell, and a high photocurrent density of −15.9 mA cm−2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n+Si/Pt photocathode in 1 m NaOH under simulated 1‐sun illumination. While this thin‐film design creates stable interfaces, the intrinsic photo‐ and electro‐degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices. [ABSTRACT FROM AUTHOR]

α‐phase formamidine lead iodine (α‐FAPbI3) as a competitive candidate to pursue high‐performance perovskite solar cells (PSCs) suffers from the weakness of random nucleation and disordered growth in chasing high‐grade polycrystalline films. Here, single‐crystal seeds crystallization (SCSC) method is proposed to obtain high‐quality α‐FAPbI3 perovskite films for the first time. Six single‐crystals seeds (CsPbBr3, CsPbI3, FAPbBr3, FAPbI3, MAPbBr3, and MAPbI3) are employed to regulate α‐FAPbI3 perovskite crystallization. These seeds act as nucleation sites and allow the perovskite to grow directly. The rapid crystallization significantly improves the crystallinity of perovskite films with uniform morphology, large grain size, and less defects. Of particular note, FAPbBr3 seed prefers to grow α‐FAPbI3 epitaxially from FAPbBr3@PbI2 heterostructure through a halogen anion exchange process. The average grain size of FAPbBr3‐perovskite film is boosted to 2.6 µm, and the trap density reduced by 11 times. The resultant FAPbBr3‐PSCs achieve a maximum power conversion efficiency (PCE) of 23.84% with a high open‐circuit voltage of 1.18 V. The unencapsulated PSC retains 91% of the initial PCE after 3000 h of storage at ≈30–50% relative humidity and preserves 98.5% of the original value after 155 h illumination with maximum power point tracking. [ABSTRACT FROM AUTHOR]

Highlights: A mixed GAI and MAI (MGM) treatment modulating the bulk and interfacial defects simultaneously is reported. The devices' performance is enhanced to ~24.5% in 0.12 cm2 and ~18.7% in 64 cm2 with improved stability. The MGM treatment can be applied to a wide range of perovskite compositions. Here, we report a mixed GAI and MAI (MGM) treatment method by forming a 2D alternating-cation-interlayer (ACI) phase (n = 2) perovskite layer on the 3D perovskite, modulating the bulk and interfacial defects in the perovskite films simultaneously, leading to the suppressed nonradiative recombination, longer lifetime, higher mobility, and reduced trap density. Consequently, the devices' performance is enhanced to 24.5% and 18.7% for 0.12 and 64 cm2, respectively. In addition, the MGM treatment can be applied to a wide range of perovskite compositions, including MA-, FA-, MAFA-, and CsFAMA-based lead halide perovskites, making it a general method for preparing efficient perovskite solar cells. Without encapsulation, the treated devices show improved stabilities. [ABSTRACT FROM AUTHOR]

Metal halide perovskite solar cells (PSCs) have been showing up in the commercial field, with an inspiring power conversion efficiency (PCE) of over 26 % in the laboratory. The quality of perovskite films is still a bottleneck due to the random and fast crystallization of ionic perovskite materials. Seeding agent‐mediated crystallization has consistently been recognized as an efficient method for preparing bulk single crystals and high‐quality films. Herein, we summarized the seeding mechanism, characterization techniques, and seeding agents working in different locations during PSC device fabrication. This Review could further facilitate researchers with a deeper understanding of seeding agents and enhance more choices for seeding crystallization to improve the performance further and the device's large‐scale fabrication toward commercialization. [ABSTRACT FROM AUTHOR]

The absent photo‐response in near‐infrared (NIR) light (>800 nm) of lead‐based perovskite solar cells (PSCs) limits the further improvement of their power conversion efficiency (PCE). Here, a narrow bandgap p‐type phthalocyanine derivative (Copper(II) 2,3,9,10,16,17,23,24‐octakis((4‐(bis(4‐methoxyphenyl)amino)phenyl)ethynyl)phthalocyanine –8TPAEPC) with NIR absorption is synthesized to extend the photovoltaic response of perovskite to 850 nm. After doping the 8TPAEPC into the perovskite photoactive layer, the perovskite crystal quality is improved, resulting in its good electrical conductivity and less surface defects. Furthermore, the molecules stacking on the grain boundaries construct the charge transportation paths, as well as the p–n bulk heterojunction with enhanced built‐in potential. The target PSCs are optimized with notably enhanced PCE from 20% up to 22.10%, and excellent stability that is over 80% of the initial level at 70–80% relative humidity can be maintained for more than 500 h, benefiting from the improved hydrophobicity of 8TPAEPC. In addition, 8TPAEPC also serves as a dopant‐free, highly carrier‐mobile, and moreover, NIR‐responsive hole transport layer (HTL) with boosted PCE of 20.42% that reaches state of the art level among the dopant‐free metal phthalocyanines HTL‐based PSCs. [ABSTRACT FROM AUTHOR]

Poor crystallinity of perovskite and extensive defects around grain boundaries are the acknowledged hindrances to obtaining high efficiency and long‐term stability for organic metal halide perovskite solar cells (PSCs). Here, a 2D covalent organic framework (2D COF) nanosheets, [(TPA)1(TPhT)1]CN, is first in situ synthesized in a PbI2 layer with a highly crystalline structure to precisely regulate the crystallization process of perovskite in the sequential deposition method. The existence of 2D COF nanosheets can decelerate intermolecular interdiffusion and induce perovskite crystals to grow along (110) planes with enlarged grain size. Meanwhile, 2D COF nanosheets distributed around the grain boundaries reduce the defect density and promote carriers transporting in the perovskite film. The superior properties of the perovskite film afford the champion PSC device with a power conversion efficiency of 22.04%, which is over 10% higher than the control device. Moreover, the target PSC also demonstrates outstanding long‐term stability. It can maintain over 90% of its initial value after 90 days storage in ambient conditions for unencapsulated devices. This work paves a new path for regulating the crystallization process of perovskites via 2D crystalline materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of KCl treatment on SnO 2 ETL and perovskite absorber were investigated. • KCl treatment modified conduction band minimum and Fermi energy so as to improve band alignment between ETL and perovskite absorber. • By the KCl treatment, K + ion diffused into absorber and passivated defects both at perovskite/ETL interface and in bulk perovskite. • Admittance spectroscopy firstly showed direct evidence of the defect passivation via the diffused K + ion. • Due to better band alignment and defect passivation, J-V hysteresis was diminished in the KCl-treated cell. SnO 2 has been studied intensively as an electron transport layer (ETL) for highly efficient metal halide perovskite solar cells. However, SnO 2 ETL frequently exhibits defect-related issues associated with the bulk SnO 2 and the perovskite/SnO 2 interface, and to passivate the defect states potassium ion has been used. In order to investigate the passivation effect of potassium ion, we carried out KCl treatment on the solution-processed SnO 2 ETL. It was found that KCl-treatment shifted up conduction band maximum and Fermi energy of SnO 2 , and reduced the band gap of perovskite absorber by K+ diffusion, which resulted in a better conduction band alignment at perovskite/SnO 2. Admittance spectroscopy revealed that diffused K+ ions can passivate defects of the perovskite absorber layer. With the improvement of band alignment and defect passivation via the KCl treatment, the J-V hysteresis was almost eliminated and power conversion efficiency was much enhanced with improved open-circuit voltage and fill factor. [ABSTRACT FROM AUTHOR]

The performance of three-dimensional (3D) organic-inorganic halide perovskite solar cells (PSCs) can be enhanced through surface treatment with 2D layered perovskites that have efficient charge transport. We maximized hole transport across the layers of a metastable Dion-Jacobson (DJ) 2D perovskite that tuned the orientational arrangements of asymmetric bulky organic molecules. The reduced energy barrier for hole transport increased out-of-plane transport rates by a factor of 4 to 5, and the power conversion efficiency (PCE) for the 2D PSC was 4.9%. With the metastable DJ 2D surface layer, the PCE of three common 3D PSCs was enhanced by approximately 12 to 16% and could reach approximately 24.7%. For a triple-cation-mixed-halide PSC, 90% of the initial PCE was retained after 1000 hours of 1-sun operation at ~40°C in nitrogen. [ABSTRACT FROM AUTHOR]

Highly efficient organic–inorganic hybrid perovskite solar cells (OIHP‐SCs) are often fabricated on a transparent conducting oxide (TCO) substrate such as indium tin oxide (ITO). However, the presence of TCOs is disadvantageous to the development of flexible OIHP‐SCs due to the brittle nature of ITO which is easily breakable during bending. Herein, a flexible TCO‐free OIHP‐SC is demonstrated by using lithium bis(trifluoromethane)sulfonimide (Li‐TFSI) as a codopant for the single‐layer graphene transparent conducting electrode and poly(triarylamine) hole‐transporting material (HTM) on a flexible polydimethylsiloxane substrate. The optical and electrical properties of the Li‐TFSI‐doped graphene substrate are measured by controlling the doping amount and the best conditions for charge extraction are established at a doping concentration of 20 mm Li‐TFSI, thus optimizing the device photovoltaic performance. As a result, a highest power conversion efficiency of 19.01% is demonstrated by the flexible TCO‐free OIHP‐SC devices with an active area of 1 cm2. In addition, the flexible TCO‐free OIHP‐SCs exhibit good bending stability after 5000 bending cycles at radii of 6, 4, and 2 mm and excellent light soaking stability under 1 Sun light intensity over 1000 h as opposed to the poor stability when using poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate as the HTM. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) Ruddlesden–Popper-type perovskites, possessing tunable bandgap, narrow light emission, strong quantum confinement effect, as well as a simple preparation method, are identified as a new generation of candidate materials for efficient light-emitting diodes. However, the preparation of high-quality quasi-2D perovskite films is still a challenge currently, such as the severe mixing of phases and a high density of defects within the films, impeding the further promotion of device performance. Here, we prepared the quasi-2D PEA2MAn−1PbnBr3n+1 perovskite films by a modified spin-coating method, and the phases with large bandgap were effectively suppressed by the vacuum evaporation treatment. We systematically investigated the optical properties and stability of the optimized films, and the photoluminescence (PL) quantum yield of the treated films was enhanced from 23% to 45%. We also studied the emission mechanisms by temperature-dependent PL spectra. Moreover, the stability of films against moisture, ultraviolet light, and heat was also greatly improved. [ABSTRACT FROM AUTHOR]

Metal halide perovskite solar cells (PSCs) have risen in efficiency from just 3.81% in 2009 to over 25.2% today. While metal halide perovskites have excelled in efficiency, advances in stability are significantly more complex and have progressed more slowly. The advance of efficiency, which is readily measured, over stability, which can require literally thousands of hours to demonstrate, is to be expected given the rapid rate of innovation in the field. In the face of changing absorber composition, synthetic approaches, and device stack components it is necessary to understand basic material properties to rationalize how to enable stability in devices. In this article the aim is to present an in‐depth review of the current understanding of metal halide perovskite devices and module stability by focusing on what is known retarding intrinsic and extrinsic degradation mechanisms at the material, device, and module level. Once these considerations are presented the discussion then moves to connecting different degradation mechanisms to stresses anticipated in operation and how they can impact efficiency of cells and ultimately modules over time. [ABSTRACT FROM AUTHOR]

The replacement of a small amount of organic cations with bulkier organic spacer cations in the perovskite precursor solution to form a 2D perovskite passivation agent (2D‐PPA) in 3D perovskite thin films has recently become a promising strategy for developing perovskite solar cells (PSCs) with long‐term stability and high efficiency. However, the long, bulky organic cations often form a barrier, hindering charge transport. Herein, for the first time, 2D‐PPA engineering based on wide‐bandgap (≈1.68 eV) perovskites are reported. Pentafluorophenethylammonium (F5PEA+) is introduced to partially replace phenylethylammonium (PEA+) as the 2D‐PPA, forming a strong noncovalent interaction between the two bulky cations. The charge transport across and within the planes of pure 2D perovskites, based on mixed ammoniums, increases by a factor of five and three compared with that of mono‐cation 2D perovskites, respectively. The perovskite films based on mixed‐ammonium (F5PEA+‐PEA+) 2D‐PPA exhibit similar surface morphology and crystal structure, but longer carrier lifetime, lower exciton binding energy, less trap density and higher conductivity, in comparison with those using mono‐cation (PEA+) 2D‐PPA. The performance of PSCs based on mixed‐cation 2D‐PPA is enhanced from 19.58% to 21.10% along with improved stability, which is the highest performance for reported wide‐bandgap PSCs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have reached a certified 25.2% efficiency in 2019 due to their high absorption coefficient, high carrier mobility, long diffusion length, and tunable direct bandgap. However, due to the nature of solution processing and rapid crystal growth of perovskite thin films, a variety of defects can form as a result of the precursor compositions and processing conditions. The use of additives can affect perovskite crystallization and film formation, defect passivation in the bulk and/or at the surface, as well as influence the interface tuning of structure and energetics. Here, recent progress in additive engineering during perovskite film formation is discussed according to the following common categories: Lewis acid (e.g., metal cations, fullerene derivatives), Lewis base based on the donor type (e.g., O‐donor, S‐donor, and N‐donor), ammonium salts, low‐dimensional perovskites, and ionic liquid. Various additive‐assisted strategies for interface optimization are then summarized; additives include modifiers to improve electron‐ and hole‐transport layers as well as those to modify perovskite surface properties. Finally, an outlook is provided on research trends with respect to additive engineering in PSC development. [ABSTRACT FROM AUTHOR]

Lead‐free halide perovskite nanocrystals (NCs) have drawn wide attention for solving the problem of lead perovskites toxicity and instability. Herein, we synthesize the direct band gap double perovskites undoped and Ag‐doped Cs2NaInCl6 NCs by variable temperature hot injection. The Cs2NaInCl6 NCs have little photoluminescence because of dark self‐trapped excitons (STEs). The dark STEs can be converted into bright STEs by doping with Ag+ to produce a bright yellow emission, with the highest photoluminescence quantum efficiency of 31.1 %. The dark STEs has been directly detected experimentally by ultrafast transient absorption (TA) techniques. The dynamics mechanism is further studied. In addition, the Ag‐doped NCs show better stability than the undoped ones. This result provides a new way to enhance the optical properties of lead‐free perovskites NCs for high‐performance light emitters. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid two‐dimensional (2D) perovskites (n≤5) have recently attracted significant attention because of their promising stability and optoelectronic properties. Normally, 2D perovskites contain a monocation [e.g. methylammonium (MA+) or formamidinium (FA+)]. Reported here for the first time is the fabrication of 2D perovskites (n=5) with mixed cations of MA+, FA+, and cesium (Cs+). The use of these triple cations leads to the formation of a smooth, compact surface morphology with larger grain size and fewer grain boundaries compared to the conventional MA‐based counterpart. The resulting perovskite also exhibits longer carrier lifetime and higher conductivity in triple cation 2D perovskite solar cells (PSCs). The power conversion efficiency (PCE) of 2D PSCs with triple cations was enhanced by more than 80 % (from 7.80 to 14.23 %) compared to PSCs fabricated with a monocation. The PCE is also higher than that of PSCs based on binary cation (MA+‐FA+ or MA+‐Cs+) 2D structures. [ABSTRACT FROM AUTHOR]

Developing high‐performance hole transporting materials (HTMs) is one of the hottest topics to enhance both efficiency and stability in perovskite solar cells (PSCs). One tetraphenylbenzidine (TPB) based HTM, XY1, was designed and synthesized. XY1 exhibits suitable thermal stability, film‐forming property, and hole mobility. Notably, a power conversion efficiency (PCE) of 13.23 % under 100 mW cm−2 AM 1.5G illumination is obtained from cells by using XY1 as HTM. Moreover, the unsealed device based on XY1 maintains its initial PCE for 600 h when aged under ambient air of 40% relative humidity in the dark and dropped by 30.2% after 480 h under continuous operation at 1‐sun illumination in ambient air, respectively, which is much better than devices based on Spiro‐OMeTAD. The results demonstrate a simple molecular engineering strategy to design TPB based hole‐transporting materials for highly stable perovskite solar cells, which is important for commercial application. A low‐costTPB based HTM XY1 was synthesized and applied in PSC with a PCE of 13.23% along with outstanding stability under humidity and illumination. [ABSTRACT FROM AUTHOR]

Recent theoretical studies indicated that the Curie temperature of perovskite manganite thin films can be increased by more than an order of magnitude by applying appropriate interfacial strain to control orbital ordering. In this work, we demonstrate that the regular intercalation of BaTiO layers between LaSrMnO layers effectively enhances ferromagnetic order and increases the Curie temperature of LaSrMnO/BaTiO superlattices. The preferential orbital occupancy of e( x -y) in LaSrMnO layers induced by the tensile strain of BaTiO layers is identified by X-ray linear dichroism measurements. Our results reveal that controlling orbital ordering can effectively improve the Curie temperature of LaSrMnO films and that in-plane orbital occupancy is beneficial to the double exchange ferromagnetic coupling of thin-film samples. These findings create new opportunities for the design and control of magnetism in artificial structures and pave the way to a variety of novel magnetoelectronic applications that operate far above room temperature. [ABSTRACT FROM AUTHOR]

A hole-transport material (HTM), 1,1,2,2-tetrakis[4-(3,6-di- tert-butyl-9 H-carbazol-9-yl)phenyl]ethene (TTBCPE), was prepared straightforwardly and employed in the fabrication of perovskite solar cells (PSCs). The investigated HTM with tetraphenylethene as the core and tert-butylcarbazole as terminal units was synthesized in two steps from commercially available and cheap raw materials. The devices based on TTBCPE without the use of any dopants and additives exhibited a power conversion efficiency (PCE) of 12.65 %, which is comparable to 14.46 % obtained by using devices based on 2,2′,7,7′-tetrakis( N, N′ -di- p-methoxyphenylamino)-9,9′-spirobifluorene ( p-doped spiro-OMeTAD). Importantly, the device based on TTBCPE showed a higher stability than devices based on doped spiro-OMeTAD if stored under ambient conditions. In this regard, this easily synthesized and dopant-free system paves a new way to develop low-cost HTMs. [ABSTRACT FROM AUTHOR]

A star-shaped hole-transporting material (HTM) using the triphenylamine (TPA) as the core named TP1 is designed and synthesized. The implementation of the new HTM in CH3NH3PbI3-based perovskite solar cells exhibits an excellent overall power conversion efficiency (PCE) of 12.63 % without the use of any dopants and additives, which is comparable to the 14.93 % obtained using p-doped spiro-OMeTAD. Importantly, the devices based on TP1 show relatively stable device performance compared to spiro-OMeTAD after aging in ambient air with 30 % relative humidity without encapsulation in the dark. The present results demonstrate that TPA could be an excellent building block to design dopant-free HTMs for perovskite solar cells and holds promise to replace p-doped spiro-OMeTAD, which is important for the fabrication of cost-effective and stable devices. [ABSTRACT FROM AUTHOR]

Despite the rapid increase in the performance of perovskite solar cells (PSC), they still suffer from low lab-to-lab or people-to-people reproducibility. Aiming for a universal condition to high-performance devices, we investigated the morphology evolution of a composite perovskite by tuning annealing temperature and precursor concentration of the perovskite film. Here, we introduce thermal annealing as a powerful tool to generate a well-controlled excess of PbI2 in the perovskite formulation and show that this benefits the photovoltaic performance. We demonstrated the correlation between the film microstructure and electronic property and device performance. An optimized average grain size/thickness aspect ratio of the perovskite crystallite is identified, which brings about a highly reproducible power conversion efficiency (PCE) of 19.5 %, with a certified value of 19.08 %. Negligible hysteresis and outstanding morphology stability are observed with these devices. These findings lay the foundation for further boosting the PCE of PSC and can be very instructive for fabrication of high-quality perovskite films for a variety of applications, such as light-emitting diodes, field-effect transistors, and photodetectors. [ABSTRACT FROM AUTHOR]

2,9,16,23-Tetrakis(7-coumarinoxy-4-methyl)- phthalocyanineiron (II) (FePc-Cou) and 2,9,16,23-tetrakis(7-coumarinoxy-4-methyl)- phthalocyaninenickel (II) (NiPc-Cou) have been synthesized and applied in perovskite solar cell as hole transporting materials(HTMs). The ground state absorption, fluorescence properties and thermal properties of FePc-Cou and NiPc-Cou have been investigated at the same time. Furthermore, Density Functional Theory (DFT) calculations show that FePc-Cou and NiPc-Cou are fit for HTMs in perovskite solar cells and their LUMO and HOMO levels are favorably positioned for injecting electrons and scavenging holes. The devices based on NiPc-Cou achieve a high open-circuit voltage of 1.061 V with a maximum power conversion efficiency (PCE) of 10.23% under AM1.5G standard conditions while the devices based on FePc-Cou obtained a PCE of 9.40%. Moreover,the devices present a good stability when in ambient air of 30% relative humidity. [ABSTRACT FROM AUTHOR]

Two hole-transporting materials (HTMs) based on N, N, N′,N′- tetraphenylbenzidine (TPB) and MeO-triphenylamine (MOTPA) are synthesized. The HTMs offer outstanding thermal stability, film-forming properties, and hole mobilities. Perovskite solar cells (PSCs) are prepared using either pristine HTM layers or layers doped with cobalt salts. The nondoped PSCs with as-synthesized HTMs show better performance compared to spiro-OMeTAD, especially for long-time stability in ambient air. The power conversion efficiency (PCE) of the cells decreases by only 3 % after 600 h of storage. The nondoped hole-transport layer (HTL) are hydrophobic, with a contact angle of 94.3° to water. The moisture-repelling ability of these HTMs are demonstrated by exposing the nondoped PSCs to an atmosphere saturated with water vapor. The PCE of doped PSCs with spiro-OMeTAD as HTL decreased 53 %, while that of nondoped PSCs with the as-synthesized HTMs as HTL only decreased 27 % after 15 min. These result thus show a new method to improve the operational stability of PSCs, especially at high humidity levels. [ABSTRACT FROM AUTHOR]

Two star-shaped TPA-based small-molecule materials (Z1012 and Z1013) were designed and synthesized in this paper. These molecules show high hole mobility and suitable energy levels for CH 3 NH 3 PbI 3 -based perovskite solar cells. Photovoltaic cells based on the Z1013 without any dopants or additives achieve an excellent power conversion efficiency (PCE) of 15.4%, which is comparable to devices based on state-of-art p-doped spiro -OMeTAD. Moreover, the devices based on these two HTMs show much better stability than that of devices based on spiro -OMeTAD when aging in ambient air both at room temperature and 80 °C. These results demonstrate that star-shape TPAs could be excellent dopant-free HTMs for perovskite solar cells and hold promise to replace the p-doped spiro -OMeTAD, which is important for the fabrication of cost-effective and stable devices. [ABSTRACT FROM AUTHOR]

We report for the first time on both interface modification and co-sensitization by using novel asymmetry 7-coumarinoxy-4-methyltetrasubstituted metallophthalocyanines in a heterojunction solar cell. The short circuit photocurrent of mesoscopic heterojunction solar cell exhibits an improvement of more than 8%, while the PCEs give an increase of more than 28% compared to CH 3 NH 3 PbI 3 -sensitized devices, and the power conversion efficiencies reached at 13.96% most. The introduction of novel asymmetry metallophthalocyanines can not only favor crystal growth of CH 3 NH 3 PbI 3 leading to a better carrier collection and retardation of charge recombination but also improve the light harvesting ability of perovskite resulting in a faster electron injection. Moreover, it can also reduce the hysteresis. [ABSTRACT FROM AUTHOR]

Three novel hole-transporting materials (HTMs) using the 4-methoxytriphenylamine (MeOTPA) core were designed and synthesized. The energy levels of the HTMs were tuned to match the perovskite energy levels by introducing symmetrical electron-donating groups linked with olefinic bonds as the π bridge. The methylammonium lead triiodide (MAPbI3) perovskite solar cells based on the new HTM Z34 (see main text for structure) exhibited a remarkable overall power conversion efficiency (PCE) of 16.1 % without any dopants or additives, which is comparable to 16.7 % obtained by a p-doped 2,2′,7,7′-tetrakis-( N, N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD)-based device fabricated under the same conditions. Importantly, the devices based on the three new HTMs show relatively improved stability compared to devices based on spiro-OMeTAD when aged under ambient air containing 30 % relative humidity in the dark. [ABSTRACT FROM AUTHOR]

In recent years, the lead-halide perovskite materials have shown great potential in lighting fields due to their excellent photoelectric properties. However, lead toxicity and instability severely limit their practical application and commercial development. In this work, zero-dimensional vacancy-ordered double perovskite Rb 2 ZrCl 6 microcrystal was synthesized by hydrothermal method for the first time. The Rb 2 ZrCl 6 microcrystals exhibit a blue-white light emission with high photoluminescence quantum yield of 60% and a large Stokes shift. The Rb 2 ZrCl 6 has a high exciton binding energy and a strong electron-phonon coupling, which supports the formation of self-trapped excitons under light excitation and the generation of broadband emission. In addition, the Rb 2 ZrCl 6 microcrystals show a remarkable stability against heat, ultraviolet light and environmental water/oxygen. Afterwards, we used the Rb 2 ZrCl 6 microcrystals as the phosphors to fabricate a white light-emitting diode (WLED). The device demonstrates a color coordinate of (0.30, 0.32), a high color rendering of 90.0, and a good working stability, with no emission degradation over continuous 10 h operation. Together with the eco-friendly features and low-cost solution processability, the nontoxic Rb 2 ZrCl 6 can therefore be deemed as a reliable light emitter for high-performance WLEDs. • The Rb 2 ZrCl 6 microcrystals exhibited a broadband blue-white emission with a large PLQY of 60%. • The broadband emission characteristic of Rb 2 ZrCl 6 originates from the self-trapped excitons emission. • The Rb 2 ZrCl 6 sample exhibit a good stability against heat, UV light and environmental water/oxygen. • The WLED prepared by Rb 2 ZrCl 6 as down-conversion phosphors have high color rendering and good stability. [ABSTRACT FROM AUTHOR]

A triphENylamine based molecular “butterfly” is developed as dopant ‐ free hole ‐ transport material for perovskite solar cells exhibiting excellENt power conversion efficiENcy of 16.3% which is comparable to the state ‐ of ‐ the ‐ art doped 2,2′,7,7′ ‐ tetrakis(N,N′ ‐ di ‐ p ‐ methoxy ‐ phENylamine) ‐ 9,9′ ‐ spirobifluorENe (spiro ‐ OMeTAD). Moreover, the device is much more stable than that of spiro ‐ OMeTAD based device under light irradiation. [ABSTRACT FROM AUTHOR]

Reduced‐dimensional hybrid perovskite semiconductors have recently attracted significant attention due to their promising stability and optoelectronic properties. However, the issue of poor charge transport in 2D perovskites limits its application. Here, studies on intermediate‐controlled crystal growth are reported to improve charge carrier transport in 2D perovskite thin films. It is shown that the coordination strength of solvents with perovskite precursor affects the initial state of intermediate phase formation as well as the subsequent perovskite layer growth. Tuning the solvent composition with a mixture (5:5) of dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) leads to the growth of highly orientated 2D perovskite films with much‐improved optoelectronic properties (faster transport by ≈50x, longer carrier lifetime by ≈4x, and lower defect density by ≈30x) than the film prepared with pure DMF. Consequently, perovskite solar cells based on DMF/DMSO (5:5) show >80% efficiency improvement than the devices based on pure DMF. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) possess both high‐power conversion efficiency (PCE) and good operation stability for future application. Although many different types of hole‐transporting materials (HTMs) are assessed, few dopant‐free small organic molecule HTMs‐based PSC cells exist, which exhibit excellent stability under both heat and illumination. Herein, two novel HTMs that are based on 9‐(4‐methoxyphenyl) carbazole and benzodithiophene cores are synthesized and named N1,N1′‐(9‐(4‐methoxyphenyl)‐9H‐carbazole‐3,6‐diyl)bis(N1‐(4‐(bis(4‐methoxyphenyl)amino)phenyl)‐N4,N4‐bis(4‐methoxyphenyl)benzene‐1,4‐diamine) (PhCz‐4MeOTPA) and N1,N1′‐(benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)bis(N1‐(4‐(bis(4‐methoxyphenyl)amino)phenyl)‐N4,N4‐bis(4‐methixyphenyl)benzene‐1,4‐diamine) (BDT‐4MeOTPA). Of the two HTMs, PhCz‐4MeOTPA possesses a lower level of planarity than that of BDT‐4MeOTPA, which inhibits molecular stacking to improve film quality and increases hole‐transport mobility and charge transport. A PCE of 16.04% is achieved with the application of dopant‐free PhCz‐4MeOTPA in PSCs, which is higher than that of dopant‐free BDT‐4MeOTPA. The unencapsulated PSC devices based on PhCz‐4MeOTPA maintain 82% of their initial values under continuous sun illumination in an ambient environment at 40–45 °C after 672 h and 92% of their initial values at 80 °C in an ambient environment after 1200 h in the dark. [ABSTRACT FROM AUTHOR]

Two simple hole-transporting materials, Me-QTPA and Me-BPZTPA, which consist of p -π conjugated structure, have been synthesized and studied in solid-state perovskite solar cells. Me-QTPA and Me-BPZTPA show outstanding thermal stabilities and appropriate HOMO levels; in addition, these two materials show wide band gaps, thus they can block the electron transport and hence suppress the carrier recombination. The solution-processed CH 3 NH 3 PbI 3 -based device using dopant-free Me-QTPA and Me-BPZTPA can achieve a power conversion efficiency of 9.07% and 8.16%, respectively. The perovskite solar cells with dopant-free Me-QTPA show better performance than the cells with dopant-free spiro -OMeTAD, especially in long-term stability. The power conversion efficiency for the perovskite solar cells with dopant-free Me-QTPA remains almost constant after 600 h. The dopant-free Me-QTPA layer shows strong hydrophobicity with a contact angle of 101.6° to water, which indicates that Me-QTPA has a promising long-term stability at room temperature. [ABSTRACT FROM AUTHOR]

• The perovskite film was prepared by ultrasonic spraying method. • Isopropyl alcohol (IPA), a green solvent with low boiling point, was introduced into perovskite precursor solution. • IPA-based PSCs exhibit the champion device efficiency of 22.43 %. The ultrasonic spray coating has been shown to be an effective technique for scaling up production. The nucleation and crystallization process of the perovskite film prepared by the ultrasonic spraying approach is more complicated than that by the spin coating, but they are essential to gaining efficient perovskite solar cells (PSCs). At the same time, the green solvent is the primary problem that must be solved in the process of PSCs commercialization. In this paper, the low boiling point and green solvent isopropyl alcohol (IPA) is introduced into the perovskite precursor solution to prepare FAPbI 3 perovskite by ultrasonic spraying. The addition of IPA enhanced the saturated vapor pressure of the precursor solution, which can create the local chemical microenvironment on the film surface and subsequently retard the nucleation rate from 8.31 s to 8.54 s at nucleation stage. The local chemical improves the initial homogeneity of the sol–gel phase and then leads to improved structural and optoelectronic properties within the FAPbI 3 film via sufficient crystallization from the sol–gel phase to α-FAPbI 3. Ultimately, IPA-based PSCs exhibit the champion device efficiency of 22.43 %. The good long-term stability of PSCs (maintain more than 90 % of the initial efficiency after 1000 h, and keep 80 % after 400 h) in ambient conditions. [ABSTRACT FROM AUTHOR]

All-perovskite-based polycrystalline thin-film tandem solar cells have the potential to deliver efficiencies of >30%. However, the performance of all-perovskite-based tandem devices has been limited by the lack of high-efficiency, low-band gap tin-lead (Sn-Pb) mixed-perovskite solar cells (PSCs).We found that the addition of guanidinium thiocyanate (GuaSCN) resulted in marked improvements in the structural and optoelectronic properties of Sn-Pb mixed, low-band gap (~1.25 electron volt) perovskite films. The films have defect densities that are lower by a factor of 10, leading to carrier lifetimes of greater than 1 microsecond and diffusion lengths of 2.5 micrometers. These improved properties enable our demonstration of >20% efficient low-band gap PSCs. When combined with wider-band gap PSCs, we achieve 25% efficient four-terminal and 23.1% efficient two-terminal all-perovskite-based polycrystalline thin-film tandem solar cells. [ABSTRACT FROM AUTHOR]

Abstract Three novel dopant-free hole-transporting materials (HTMs) based on phthalocyanine core containing (4-methyl formate) phenoxy or (4-butyl formate) phenoxy as the peripheral groups with cupper or zinc as the core metals (CuPcNO 2 -OMFPh, CuPcNO 2 -OBFPh, ZnPcNO 2 -OBFPh) were designed and synthesized. All of the phthalocyanine complexes show excellent thermal stabilities, appropriate energy levels and suitable hole mobilities. The potential of three HTMs were tested in perovskite solar cells (PSCs) and ZnPcNO 2 -OBFPh based PSC obtained power conversion efficiency (PCE) of 15.74% under 100 mA cm−2 standard AM 1.5G solar illumination. Most important of all, PSC based on ZnPcNO 2 -OBFPh shows better stability than that of the other two phthalocyanines and Spiro-OMeTAD under continuous light irradiation at 60 °C and maximum power point tracking in ambient air without encapsulation after 500 h. The results show that the introduction of appropriate peripheral groups and core metals can improve the performance and stability of PSCs dramatically, which provides an alternative way to develop HTMs for efficient and stable PSCs. Graphical abstract Image 1 Highlights • Novel asymmetric metallophthalocyanines (CuPcNO 2 -OMFPh, CuPcNO 2 -OBFPh and ZnPcNO 2 -OBFPh) were synthesized. • They were applied in perovskite solar cells as hole transporting material. • The cell devices based on ZnPcNO 2 -OBFPh show excellent stability under continuous light irradiation. • The power conversion efficiency of the device based on dopant-free ZnPcNO 2 -OBFPh is up to 15.74%. [ABSTRACT FROM AUTHOR]

• A green anti-solvent EA method for MA-free quasi-2D DJ phase perovskite films with was reported. • The films presented a more homogeneous phase distribution with reduced defect density, higher mobility and conductivity. • A PCE of 18.86% was obtained, which is the highest for MA-free DJ phase 2D perovskite-based devices. • The devices maintained impressive stabilities under damp heat and continuous illumination at MPP tracking, respectively. The phase distribution of two-dimensional (2D) perovskites is critical for solar cell power conversion efficiency (PCE). Here, we report a simple green anti-solvent (ethyl acetate, EA) method for obtaining uniform phase dispersion of methylamine (MA)-free quasi-2D Dion-Jacobson (DJ) phase perovskite films (DMePDA)FA 3 Pb 4 I 13 (n = 4). The films present a more homogeneous phase distribution for their rapid extraction of solvents and the interaction between Pb2+ and the carbonyl group in EA, resulting in a more shining surface, reduced surface-defect density, higher out-plane mobility, and higher conductivity. We obtain a PCE of 18.86 %, which is the highest for MA-free DJ phase 2D perovskite-based devices. In addition, the target devices maintain 85 % and 90 % of their initial values after 1008 h under 85 % relative humidity at 85 ℃ (ISOS-D-3) and continuous illumination at maximum power point (MPP) tracking at ∼ 45 ℃ (ISOS-L-1), respectively. [ABSTRACT FROM AUTHOR]

The hole transporting materials for perovskite solar cells to increase power conversion efficiency ( PCE ) and improve the stability have been studied in recent years. In this paper, a novel asymmetric 2,9,16-triphenoxy-23-nitrophthalocyaninatocobalt (CoPcNO 2 -OPh) is synthesized, which can be employed as a promising hole transporting material in solid state perovskite solar cells. The three phenoxy groups introduced into phthalocyanine complex improved the solubility and inhibit the aggregation effectively. This material shows strong absorption and high thermal stability. The density functional theory (DFT) method of frontier molecular orbitals shows that the introduction of phenoxy and nitro can adjust the energy levels of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) to −5.14 eV and −3.05 eV respectively, indicating that CoPcNO 2 -OPh can be used as an hole transporting material. The optimized devices achieved a high open-circuit voltage of 1.04 V with a maximum power conversion efficiency of 8.24% under AM1.5 G standard conditions. The introduction of this new HTM offers a new and effective tool towards engineering the stability for large-scale applications. [ABSTRACT FROM AUTHOR]

A novel layered organometal halide perovskite material (CH 3 NH 3 ) 2 Pb(SCN) 2 I 2 was acquired by replacing the iodide ions locating on the axial positions of CH 3 NH 3 PbI 3 octahedron with thiocyanide anions. The molecular structure of this material was characterized by X-ray single crystal diffraction, through which the thiocyanides were proved to be coordinated as terminal ligands on the lead center. A variety of spectral tests reveal material’s energy gap ( E g ) and valence band (VB) as 1.65 eV and −5.76 eV, respectively. The concentration of holes has also been located as up to 1.07 × 10 14 cm −3 via Hall effect measurement. What is important, for the material shows great solubility and crystallinity in low boiling-point solvent tetrahydrofuran, excellent film morphology can be achieved via a convenient and practical one-step precursor solution-deposition method without thermal annealing. The fill factor (FF) of solar cell devices based on this material can be promoted as much as 0.725. [ABSTRACT FROM AUTHOR]