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Two‐dimensional materials have been widely used to tune the growth and energy‐level alignment of perovskites. However, their incomplete passivation and chaotic usage amounts are not conducive to the preparation of high‐quality perovskite films. Herein, we succeeded in obtaining higher‐quality CsPbBr3 films by introducing large‐area monolayer graphene as a stable physical overlay on top of TiO2 substrates. Benefiting from the inert and atomic smooth graphene surface, the CsPbBr3 film grown on top by the van der Waal epitaxy has higher crystallinity, improved (100) orientation, and an average domain size of up to 1.22 μm. Meanwhile, a strong downward band bending is observed at the graphene/perovskite interface, improving the electron extraction to the electron transport layers (ETL). As a result, perovskite film grown on graphene has lower photoluminescence (PL) intensity, shorter carrier lifetime, and fewer defects. Finally, a photovoltaic device based on epitaxy CsPbBr3 film is fabricated, exhibiting power conversion efficiency (PCE) of up to 10.64% and stability over 2000 h in the air. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

Organic solar cells (OSCs) have been attracting considerable interest due to their unique advantages of low cost, light weight, and especially mechanical flexibility. The low-cost and high-throughput techniques matching with the large-scale and roll-to-roll (R2R) process for fabricating efficient OSCs in the ambient condition would greatly accelerate the potential commercialization of OSCs. Herein, we demonstrate that the fabrication processes of OSCs using the bulk heterojunction (BHJ) composed of poly[(2,6–(4,8-bis(5–(2-ethylhexy)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5–(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′5′-c′]dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(2-methylene-(3–(1,1-dicyanomethylene)-5-methylindanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]-dithiophene (IT-M) are transferred from a glovebox to the ambient condition, where the deposition of doctor blading instead of conventional spin coating is investigated. The morphology, microphase separation, and crystallinity of BHJ PBDB-T:IT-M are dramatically influenced by the fabrication processes. The OSCs with a structure of ITO/ZnO/PBDB-T:IT-M/MoO3/Ag fabricated via doctor-blading in the ambient condition show a power conversion efficiency (PCE) of 9.0% as compared to conventional spin-coated OSCs in a glovebox with a PCE of 11.91% and in the ambient condition with a PCE of 9.91%. These results suggest that efficient OSCs could be processed in the ambient condition by large-scale and low-cost doctor-blading, which can be compatible with the R2R manufacturing process. [ABSTRACT FROM AUTHOR]

ABSTRACT Two novel polymeric acceptors based on naphthalene diimide (NDI) and 2.2′-bithiophene, named as P(NDI2THD-T2) and P(NDI2TOD-T2), were designed and synthesized for all polymer solar cells application. The structural and electronic properties of the two acceptors were modulated through side-chain engineering of the NDI units. The optoelectronic properties of the polymers and the morphologies of the blend films composed of the polymer acceptors and a donor polymer PTB7-Th were systemically investigated. With thiophene groups introduced into the side chains of the NDI units, both polymers showed wider absorption from 350 nm to 900 nm, compared with the reference polymer acceptor of N2200. No redshift of absorption spectra from solutions to films indicated reduced aggregation of the polymers due to the steric hindrance effect of thiophene rings in the side chains. The photovoltaic performance were characterized for devices in a configuration of ITO/PEDOT:PSS/PTB7-Th:acceptors/2,9-bis(3-(dimethylamino)propyl)anthra[2,1,9-def:6,5,10-def]diisoquinoline-1,3,8,10(2H,9H)-tetraone (PDIN)/Al. With the addition of diphenyl ether as an additive, the power conversion efficiencies (PCEs) of 2.73% and 4.75% for P(NDI2THD-T2) and P(NDI2TOD-T2) based devices were achieved, respectively. The latter showed improved Jsc, Fill Factor (FF), and PCE compared with N2200 based devices. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3679-3689 [ABSTRACT FROM AUTHOR]

Derived from perylenediimide (PDI) building blocks, 3D PDI molecules are considered as a type of promising structure to overcome molecular aggregation, thus improving the performance of organic solar cells. Herein, we report a novel PDI-based derivative, SCPDT-PDI4, with four PDI units connected to a unique spiro core. Attributed to this novel molecular design, SCPDT-PDI4 exhibits a rigid 3D structure, in which the aggregation tendency of PDI chromophores could be effectively attenuated. Additionally, strong intramolecular charge transfer and high charge mobility are achieved due to the well-conjugated structure and electron-rich property of SCPDT. Therefore, fullerene-free organic solar cells based on SCPDT-PDI4 and PTB7-Th achieve a remarkable high efficiency of 7.11 %. Such an excellent result demonstrates the opportunity of SCPDT to be a promising building block for non-fullerene acceptors. [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]

Recently, considerable researches have reported that the incorporation of potassium cation (K+) in lead halide perovskites obviously improves the performance of perovskite solar cells. The recent finding indicates that the interstitial occupancy position of K+ in perovskite lattice can increase ion‐migration barrier, which dramatically suppresses the hysteresis of the device. However, the enhancement of photoluminescence (PL) as well as bandgap variation cannot be interpreted by K+ interstitial state in perovskite. Considering this discrepancy, it has been found out that potassium‐rich phase grows in three dimensional (3D) perovskite crystal grain boundary through both experiments and theoretical simulations, which can efficiently passivate the grain boundaries on the 3D crystal surface and decrease trap states. Meanwhile, the dielectric confinement effect between potassium‐rich phase and 3D perovskite crystal, contributing to improvement of radiative recombination in perovskite absorber, can further support the enhancement and red‐shift of photoluminescence (PL) spectrum. Therefore, a power conversion efficiency of 20.4% has been achieved in K+ doped halide perovskite solar cell, and still maintains 90% initial efficiency after stored in 30% humidity at room temperature for 1000 h. These findings offer a new path for the structural manipulation by incorporating multi cations in perovskite materials. [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]

Up the junction: A non ‐ fullerene acceptor, SCPDT ‐ PDI4, composed of perylenediimide (PDI) and a spiro core of 4,4’ ‐ spirobi[cyclopenta[2,1 ‐ b;3,4 ‐ b’]dithiophene] (SCPDT), has been developed. SCPDT ‐ PDI4 exhibits a unique 3D structure and isotropic charge transport properties. Organic solar cells based on SCPDT ‐ PDI4 and a donor polymer of poly[4,8 ‐ bis(5 ‐ (2 ‐ ethylhexyl)thiophen ‐ 2 ‐ yl)benzo[1,2 ‐ b;4,5 ‐ b’]di ‐ thiophene ‐ 2,6 ‐ diyl ‐ alt ‐ (4 ‐ (2 ‐ ethylhexyl) ‐ 3 ‐ fluorothieno[3,4 ‐ b]thiophene ‐ ) ‐ 2 ‐ carboxylate ‐ 2–6 ‐ diyl)] PTB7 ‐ Th achieved a remarkable quantum efficiency of 7.11%, indicating SCPDT ‐ PDI4 is a very promising non ‐ fullerene acceptor for organic solar cells. More information can be found in the Communication by Fei Chen, Zongxiang Xu, Zhi ‐ Kuan Chen, Wei Huang et   al. on page   721 in Issue 7, 2017 (DOI: 10.1002/asia.201601741). [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]

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]

[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]