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A universal and stable photovoltaic cell based on Cs_0.05MA_0.95PbBr _x I_{3− x} perovskite and Nb:TiO₂ electron transport layer is reported to harvest artificial light by a synergetic manipulating strategy. Morphology, composition, and energy band engineering produce a remarkable power conversion efficiency of 36.3%. Diverse practical applications are successfully demonstrated by the online driving of a sodium‐ion battery and electronic devices.

Abstract

As the fastest developing photovoltaic device, perovskite solar cells have achieved an extraordinary power conversion efficiency (PCE) of 25.3% under AM 1.5 illumination. However, few studies have been devoted to perovskite solar cells harvesting artificial light, owing to the great challenge in the simultaneous manipulation of bandgap‐adjustable perovskite materials, corresponding matched energy band structure of carrier transport materials, and interfacial defects. Herein, through systematic morphology, composition, and energy band engineering, high‐quality Cs_0.05MA_0.95PbBr _x I_{3− x} perovskite as the light absorber and Nb _y Ti_{1− y} O₂ (Nb:TiO₂) as the electron transport material with an ideal energy band alignment are obtained simultaneously. The theoretical‐limit‐approaching record PCEs of 36.3% (average: 34.0 ± 1.2%) under light‐emitting diode (LED, warm white) and 33.2% under fluorescent lamp (cold white) are achieved simultaneously, as well as a PCE of 19.5% (average: 18.9 ± 0.3%) under solar illumination. An integrated energy conversion and storage system based on an artificial light response solar cell and sodium‐ion battery is established for diverse practical applications, including a portable calculator, quartz clock, and even environmental monitoring equipment. Over a week of stable operation shows its great practical potential and provides a new avenue to promote the commercialization of perovskite photovoltaic devices via integration with ingenious electronic devices.

The thiazolium iodide‐passivated perovskite layer reduces CH₃NH₃ ⁺ thermal diffusion and shallow as well as deep traps, which in turn yield improved performance.

Abstract

Interface engineering has become one of the most facile and effective approaches to improve solar cells performance and its long‐term stability and to retard unwanted side reactions. Three passivating agents are developed which can functionalize the surface and induce hydrophobicity, by employing substituted thiazolium iodide (TMI) for perovskite solar cells fabrication. The role of TMI interfacial layers in microstructure and electro‐optical properties is assessed for structural as well as transient absorption measurements. TMI treatment resulted in V _OC and fill factor enhancement by reducing possible recombination paths at the perovskite/hole selective interface and by reducing the shallow as well as deep traps. These in turn allow to achieve higher performance as compared to the pristine surface. Additionally, the TMI passivated perovskite layer considerably reduces CH₃NH₃ ⁺ thermal diffusion and degradation induced by humidity. The un‐encapsulated perovskite solar cells employing TMI exhibit a remarkable stability under moisture levels (≈50% RH), retaining ≈95% of the initial photon current efficiency after 800 h of fabrication, paving the way towards a potential scalable endeavor.

Superoxide formation in mesoporous carbon perovskite solar cells is dependent upon a combination of competitive factors including defect concentrations, charge carrier extraction, oxygen diffusion, and grain morphology. The addition of 5‐aminovaleric acid iodide to the methylammonium lead iodide perovskite allows the formation of smaller grains, thus hindering oxygen diffusion in the film, reducing superoxide formation.

Abstract

Perovskite solar cells have attracted a great deal of attention thanks to their high efficiency, ease of manufacturing, and potential low cost. However, the stability of these devices is considered their main drawback and needs to be addressed. Mesoporous carbon perovskite solar cells (m‐CPSC), consisting of three mesoporous layers (TiO₂/ZrO₂/C) infiltrated with CH₃NH₃PbI₃ (MAPI) perovskite, have presented excellent lifetimes of more than 10 000 h when the additive NH₂(CH₂)₄CO₂HI (5‐ aminovaleric acid iodide; 5‐AVAI) is used to modify the perovskite structure. Yet, the role of 5‐AVAI in enhancing the stability has yet to be determined. Here, superoxide‐mediated degradation of MAPI m‐CPSC with and without the 5‐AVAI additive is studied using the fluorescence probe dihydroethidium for superoxide detection. In situ X‐ray diffractometry shows that aminovaleric acid methylammonium lead iodide (AVA‐MAPI) perovskite infiltrated in mesoporous layers presents higher stability in an ambient environment under illumination, evidenced by a slower decrease of the MAPI/PbI₂ peak ratio. Superoxide yield measurements demonstrate that AVA‐MAPI generates more superoxide than regular MAPI when deposited on glass but generates significantly less when infiltrated in mesoporous layers. It is believed that superoxide formation in m‐CPSC is dependent on a combination of competitive factors including oxygen diffusion, sample morphology, grain size, and defect concentration.

Colloidal core/shell quantum dots (QDs) exhibit promising optical and electrical properties. Herein, a comprehensive overview is presented of the recent developments in the engineering of the structure of core/shell QDs to tune exciton dynamics so as to improve the performance of QD‐sensitized solar cells.

Abstract

Semiconductor nanocrystals, the so‐called quantum dots (QDs), exhibit versatile optical and electrical properties. However, QDs possess high density of surface defects/traps due to the high surface‐to‐volume ratio, which act as nonradiative carrier recombination centers within the QDs, thereby deteriorating the overall solar cell performance. The surface passivation of QDs through the growth of an outer shell of different materials/compositions called “core/shell QDs” has proven to be an effective approach to reduce the surface defects and confinement potential, which can enable the broadening of the absorption spectrum, accelerate the carrier transfer, and reduce exciton recombination loss. Here, the recent research developments in the tailoring of the structure of core/shell QDs to tune exciton dynamics so as to improve solar cell performance are summarized. The role of band alignment of core and shell materials, core size, shell thickness/compositions, and interface engineering of core/thick shell called “giant” QDs on electron–hole spatial separation, carrier transport, and confinement potential, before and after grafting on the carrier scavengers (semiconductor/electrolyte), is described. Then, the solar cell performance based on core/shell QDs is introduced. Finally, an outlook for the rational design of core/shell QDs is provided, which can further promote the development of high‐efficiency and stable QD sensitized solar cells.

The thiazolium iodide‐passivated perovskite layer reduces CH₃NH₃ ⁺ thermal diffusion and shallow as well as deep traps, which in turn yield improved performance.

Abstract

Interface engineering has become one of the most facile and effective approaches to improve solar cells performance and its long‐term stability and to retard unwanted side reactions. Three passivating agents are developed which can functionalize the surface and induce hydrophobicity, by employing substituted thiazolium iodide (TMI) for perovskite solar cells fabrication. The role of TMI interfacial layers in microstructure and electro‐optical properties is assessed for structural as well as transient absorption measurements. TMI treatment resulted in V _OC and fill factor enhancement by reducing possible recombination paths at the perovskite/hole selective interface and by reducing the shallow as well as deep traps. These in turn allow to achieve higher performance as compared to the pristine surface. Additionally, the TMI passivated perovskite layer considerably reduces CH₃NH₃ ⁺ thermal diffusion and degradation induced by humidity. The un‐encapsulated perovskite solar cells employing TMI exhibit a remarkable stability under moisture levels (≈50% RH), retaining ≈95% of the initial photon current efficiency after 800 h of fabrication, paving the way towards a potential scalable endeavor.

A simple low‐temperature‐processed In₂O₃/SnO₂ bilayer electron‐transport layer (ETL) is used for fabricating efficient perovskite solar cells (PSCs). The bilayer ETL with appropriate energy alignment is beneficial for charge transfer, thus minimizing open‐circuit voltage (V _OC) loss. An optimized planar PSC with a power conversion efficiency (PCE) of 23.24% is obtained. In contrast, devices based on single SnO₂ only achieve efficiency of 21.42%.

Abstract

An electron‐transport layer (ETL) with appropriate energy alignment and enhanced charge transfer is critical for perovskite solar cells (PSCs). However, interfacial energy level mismatch limits the electrical performance of PSCs, particularly the open‐circuit voltage (V _OC). Herein, a simple low‐temperature‐processed In₂O₃/SnO₂ bilayer ETL is developed and used for fabricating a new PSC device. The presence of In₂O₃ results in uniform, compact, and low‐trap‐density perovskite films. Moreover, the conduction band of In₂O₃ is shallower than that of Sn‐doped In₂O₃ (ITO), enhancing the charge transfer from perovskite to ETL, thus minimizing V _OC loss at the perovskite and ETL interface. A planar PSC with a power conversion efficiency of 23.24% (certified efficiency of 22.54%) is obtained. A high V _OC of 1.17 V is achieved with the potential loss at only 0.36 V. In contrast, devices based on single SnO₂ layers achieve 21.42% efficiency with a V _OC of 1.13 V. In addition, the new device maintains 97.5% initial efficiency after 80 d in N₂ without encapsulation and retains 91% of its initial efficiency after 180 h under 1 sun continuous illumination. The results demonstrate and pave the way for the development of efficient photovoltaic devices.

All held together: A simple post‐treatment procedure uses 2‐aminoterephthalic acid as a cross‐linking agent to modify the exposed grain boundary of a perovskite film, which is directly observed with conductive atomic force microscopy (C‐AFM). Under the optimized cross‐linking agent concentration, a solar cell achieves a power conversion efficiency (PCE) of 21.09 % and improved stability.

Abstract

Metal halide perovskite solar cells (PSCs), with their exceptional properties, show promise as photoelectric converters. However, defects in the perovskite layer, particularly at the grain boundaries (GBs), seriously restrict the performance and stability of PSCs. Now, a simple post‐treatment procedure involves applying 2‐aminoterephthalic acid to the perovskite to produce efficient and stable PSCs. By optimizing the post‐treatment conditions, we created a device that achieved a remarkable power conversion efficiency (PCE) of 21.09 % and demonstrated improved stability. This improvement was attributed to the fact that the 2‐aminoterephthalic acid acted as a cross‐linking agent that inhibited the migration of ions and passivated the trap states at GBs. These findings provide a potential strategy for designing efficient and stable PSCs regarding the aspects of defect passivation and crystal growth.

Superoxide formation in mesoporous carbon perovskite solar cells is dependent upon a combination of competitive factors including defect concentrations, charge carrier extraction, oxygen diffusion, and grain morphology. The addition of 5‐aminovaleric acid iodide to the methylammonium lead iodide perovskite allows the formation of smaller grains, thus hindering oxygen diffusion in the film, reducing superoxide formation.

Abstract

Perovskite solar cells have attracted a great deal of attention thanks to their high efficiency, ease of manufacturing, and potential low cost. However, the stability of these devices is considered their main drawback and needs to be addressed. Mesoporous carbon perovskite solar cells (m‐CPSC), consisting of three mesoporous layers (TiO₂/ZrO₂/C) infiltrated with CH₃NH₃PbI₃ (MAPI) perovskite, have presented excellent lifetimes of more than 10 000 h when the additive NH₂(CH₂)₄CO₂HI (5‐ aminovaleric acid iodide; 5‐AVAI) is used to modify the perovskite structure. Yet, the role of 5‐AVAI in enhancing the stability has yet to be determined. Here, superoxide‐mediated degradation of MAPI m‐CPSC with and without the 5‐AVAI additive is studied using the fluorescence probe dihydroethidium for superoxide detection. In situ X‐ray diffractometry shows that aminovaleric acid methylammonium lead iodide (AVA‐MAPI) perovskite infiltrated in mesoporous layers presents higher stability in an ambient environment under illumination, evidenced by a slower decrease of the MAPI/PbI₂ peak ratio. Superoxide yield measurements demonstrate that AVA‐MAPI generates more superoxide than regular MAPI when deposited on glass but generates significantly less when infiltrated in mesoporous layers. It is believed that superoxide formation in m‐CPSC is dependent on a combination of competitive factors including oxygen diffusion, sample morphology, grain size, and defect concentration.

Stable and efficient mixed tin–lead (Sn–Pb) perovskite solar cells (PSCs) are demonstrated by defect passivation with ultrathin layered perovskites. The passivation layer provides defect passivation both at the film surface and the grain boundaries, without blocking the carrier transport. The devices exhibit a certified power conversion efficiency (PCE) of 18.95%, and a 200 h diurnal operating stability.

Abstract

The development of narrow‐bandgap (E _g ≈ 1.2 eV) mixed tin–lead (Sn–Pb) halide perovskites enables all‐perovskite tandem solar cells. Whereas pure‐lead halide perovskite solar cells (PSCs) have advanced simultaneously in efficiency and stability, achieving this crucial combination remains a challenge in Sn–Pb PSCs. Here, Sn–Pb perovskite grains are anchored with ultrathin layered perovskites to overcome the efficiency‐stability tradeoff. Defect passivation is achieved both on the perovskite film surface and at grain boundaries, an approach implemented by directly introducing phenethylammonium ligands in the antisolvent. This improves device operational stability and also avoids the excess formation of layered perovskites that would otherwise hinder charge transport. Sn–Pb PSCs with fill factors of 79% and a certified power conversion efficiency (PCE) of 18.95% are reported—among the highest for Sn–Pb PSCs. Using this approach, a 200‐fold enhancement in device operating lifetime is achieved relative to the nonpassivated Sn–Pb PSCs under full AM1.5G illumination, and a 200 h diurnal operating time without efficiency drop is achieved under filtered AM1.5G illumination.

Self‐Assembled Monolayers

In article number 1900251, Jongmin Choi, Taiho Park, and co‐workers report on self‐assembled monolayers that can be anchored to metal oxides and help to transport charges from perovskite. An overview of interface engineering methods for perovskite solar cells is provided, particularly with regards to the types of self‐assembled monolayers and their roles in device energy level alignment and passivation effects.

Add the imide: A series of imide‐fused diazatetracenes were synthesized by Buchwald‐Hartwig C−N coupling. Their optical and electronic properties as well as solid‐state structures were investigated. Further application in perovskite solar cells also illustrated the electron‐transporting properties of our imide‐fused diazatetracenes (see figure).

Abstract

A series of imide‐fused diazatetracenes were synthesized via Buchwald–Hartwig C−N coupling with a highly active palladium source. The introduction of an imide segment effectively lowers the LUMO levels compared with that of unsubstituted diazatetracene. By adjusting the alkyl chains of the diazatetracenes, different solid‐state packings were achieved, resulting in distinct photoluminescent behaviors. Their electron‐transporting properties were demonstrated in the proof‐of‐concept Perovskite solar cells as electron transporting layers.

Add the imide: A series of imide‐fused diazatetracenes were synthesized by Buchwald‐Hartwig C−N coupling. Their optical and electronic properties as well as solid‐state structures were investigated. Further application in perovskite solar cells also illustrated the electron‐transporting properties of our imide‐fused diazatetracenes (see figure).

Abstract

A series of imide‐fused diazatetracenes were synthesized via Buchwald–Hartwig C−N coupling with a highly active palladium source. The introduction of an imide segment effectively lowers the LUMO levels compared with that of unsubstituted diazatetracene. By adjusting the alkyl chains of the diazatetracenes, different solid‐state packings were achieved, resulting in distinct photoluminescent behaviors. Their electron‐transporting properties were demonstrated in the proof‐of‐concept Perovskite solar cells as electron transporting layers.

Herein, calcium chloride is applied to passivate and dope inorganic CsPbI₂Br. It enhances the crystallinity of CsPbI₂Br to decrease trap density and prolong carrier lifetime and to raise its Fermi level to lie very close to the conduction band, leading to a high voltage of 1.32 V, and a record efficiency of 16.79% for CsPbI₂Br cells.

Abstract

Cesium‐based inorganic perovskites, such as CsPbI₂Br, are promising candidates for photovoltaic applications owing to their exceptional optoelectronic properties and outstanding thermal stability. However, the power conversion efficiency of CsPbI₂Br perovskite solar cells (PSCs) is still lower than those of hybrid PSCs and inorganic CsPbI₃ PSCs. In this work, passivation and n‐type doping by adding CaCl₂ to CsPbI₂Br is demonstrated. The crystallinity of the CsPbI₂Br perovskite film is enhanced, and the trap density is suppressed after adding CaCl₂. In addition, the Fermi level of the CsPbI₂Br is changed by the added CaCl₂ to show heavy n‐type doping. As a result, the optimized CsPbI₂Br PSC shows a highest open circuit voltage of 1.32 V and a record efficiency of 16.79%. Meanwhile, high air stability is demonstrated for a CsPbI₂Br PSC with 90% of the initial efficiency remaining after more than 1000 h aging in air.

High‐quality Cs₃Bi₂I₉ single crystal thin film (SCTF) with ≈1 µm in thickness and 4 mm in lateral size is grown via a space‐limited solvent evaporation crystallization method. The Cs₃Bi₂I₉ SCTF–based photodetectors exhibit superior photodetecting performance such as a high on–off ratio of 10⁴, low dark current, wide linear dynamic range, and fast response speed.

Abstract

Hybrid organic–inorganic lead halide perovskite single crystal thin film (SCTF) recently has attracted enormous interest in the field of optoelectronic devices, since it efficiently resolves the trade‐off between thickness and carrier diffusion length. However, the toxicity of lead element and the instability induced by organic component still hinder its future developments. In this work, lead‐free all‐inorganic Cs₃Bi₂I₉ SCTF with a high orientation along (00h) has been in situ grown on indium tin oxide (ITO) glass via a space‐limited solvent evaporation crystallization method. The trap density of Cs₃Bi₂I₉ SCTF (5.7 × 10¹² cm⁻³) is 263 folds lower than that of the polycrystalline thin film (PCTF) counterpart, together with a 5‐order‐of‐magnitude higher carrier mobility. These superior charge transfer properties enable a photoresponse on–off ratio as high as 11 000, which far surpasses that of the PCTF device by 460 folds, comparable to the lead halide perovskite. Furthermore, the Cs₃Bi₂I₉ SCTF photodetector exhibits outstanding stability even without any encapsulation, whose initial performance is well maintained after aging 1000 h in humid air of 50% RH or continuous on–off light illumination for 20 h. This work will pave the way to produce new families of high‐performance, stable, and nontoxic perovskite SCTF for future optoelectronic applications.

Superoxide formation in mesoporous carbon perovskite solar cells is dependent upon a combination of competitive factors including defect concentrations, charge carrier extraction, oxygen diffusion, and grain morphology. The addition of 5‐aminovaleric acid iodide to the methylammonium lead iodide perovskite allows the formation of smaller grains, thus hindering oxygen diffusion in the film, reducing superoxide formation.

Abstract

Perovskite solar cells have attracted a great deal of attention thanks to their high efficiency, ease of manufacturing, and potential low cost. However, the stability of these devices is considered their main drawback and needs to be addressed. Mesoporous carbon perovskite solar cells (m‐CPSC), consisting of three mesoporous layers (TiO₂/ZrO₂/C) infiltrated with CH₃NH₃PbI₃ (MAPI) perovskite, have presented excellent lifetimes of more than 10 000 h when the additive NH₂(CH₂)₄CO₂HI (5‐ aminovaleric acid iodide; 5‐AVAI) is used to modify the perovskite structure. Yet, the role of 5‐AVAI in enhancing the stability has yet to be determined. Here, superoxide‐mediated degradation of MAPI m‐CPSC with and without the 5‐AVAI additive is studied using the fluorescence probe dihydroethidium for superoxide detection. In situ X‐ray diffractometry shows that aminovaleric acid methylammonium lead iodide (AVA‐MAPI) perovskite infiltrated in mesoporous layers presents higher stability in an ambient environment under illumination, evidenced by a slower decrease of the MAPI/PbI₂ peak ratio. Superoxide yield measurements demonstrate that AVA‐MAPI generates more superoxide than regular MAPI when deposited on glass but generates significantly less when infiltrated in mesoporous layers. It is believed that superoxide formation in m‐CPSC is dependent on a combination of competitive factors including oxygen diffusion, sample morphology, grain size, and defect concentration.

A novel benzo[1,2‐b:4,5‐b′]difuran (BDF)‐based copolymer, L2, is designed and synthesized. When blended with a non‐fullerene small molecule acceptor TTPT‐T‐4F, the L2‐based device exhibits an efficiency of 14.0%, which is higher than that (12.72%) of its analogue benzo[1,2‐b:4,5‐b′]dithiophene (BDT) copolymer‐based device. Thus, the performance of the BDF‐based copolymers are equal to or greater than that of the BDT‐based counterparts.

Abstract

The development of high‐performance donor polymers is important for obtaining high power conversion efficiencies (PCEs) of non‐fullerene polymer solar cells (PSCs). Currently, most high‐efficiency PSCs are fabricated with benzo[1,2‐b:4,5‐b′]dithiophene (BDT)‐based conjugated polymers. The photovoltaic performance of benzo[1,2‐b:4,5‐b′]difuran (BDF)‐based copolymers has lagged far behind that of BDT‐based counterparts. In this study, a novel BDF‐based copolymer L2 is designed and synthesized, in which BDF and benzotriazole (BTz) building blocks have been used as the electron‐sufficient and deficient units, respectively. When blending with a non‐fullerene small molecule acceptor (SMA), TTPT‐T‐4F, the L2‐based device exhibits a remarkably high PCE of 14.0%, which is higher than that of the device fabricated by its analogue BDT copolymer (12.72%). Moreover, PSCs based on the L2:TTPT‐T‐4F blend demonstrate excellent ambient stability with 92% of its original PCE remaining after storage in air for 1800 h. Thus, BDF is a promising electron‐donating unit, and the BDF‐based copolymers can be competitive or even surpass the performance of BDT‐based counterparts.

Molecules with controlled electron affinity processed at low temperature are used to tailor conductivity and the energy levels of hole transporting materials (HTMs), enabling fast holes extraction at the HTM/perovskite interface. This method with novel 3,6‐difluoro‐2,5,7,7,8,8‐hexacyanoquinodimethane enables the highest reported power conversion efficiency (PCE) of 22.13% and 20.01% for NiO _x ‐based rigid and flexible perovskite solar cells, respectively.

Abstract

Inverted perovskite solar cells (PSCs) with low‐temperature processed hole transporting materials (HTMs) suffer from poor performance due to the inferior hole‐extraction capability at the HTM/perovskite interfaces. Here, molecules with controlled electron affinity enable a HTM with conductivity improved by more than ten times and a decreased energy gap between the Fermi level and the valence band from 0.60 to 0.24 eV, leading to the enhancement of hole‐extraction capacity by five times. As a result, the 3,6‐difluoro‐2,5,7,7,8,8‐hexacyanoquinodimethane molecules are used for the first time enhancing open‐circuit voltage (V _oc) and fill factor (FF) of the PSCs, which enable rigid‐and flexible‐based inverted perovskite devices achieving highest power conversion efficiencies of 22.13% and 20.01%, respectively. This new method significantly enhances the V _oc and FF of the PSCs, which can be widely combined with HTMs based on not only NiO _x but also PTAA, PEDOTT:PSS, and CuSCN, providing a new way of realizing efficient inverted PSCs.

Conductive atomic force microscopy can realize a real‐space visualization of topography coupled with electronic properties on the microscopic scale and thereby demonstrates a unique ability to probe local effects of perovskite materials and devices. This manuscript comprehensively reviews the applications in perovskite solar cells for electronic transport behavior, ion migration and hysteresis, ferroelectric polarization, and facet orientation investigation.

Abstract

Metal halide perovskite materials, benefiting from a combination of outstanding optoelectronic properties and low‐cost solution‐preparation processes, show tremendous potential for optoelectronics and photovoltaics. However, the nanoscale inhomogeneities of the electronic properties of perovskite materials cause a number of difficulties, such as recombination, stability, and hysteresis, all of which seriously restrict device performance. Scanning probe microscopy, as a high‐resolution imaging technique, has been widely used to connect local properties and micro‐area morphologies to overall device performance. Conductive atomic force microscopy (C‐AFM) can realize a real‐space visualization of topography coupled with optoelectronic properties on a microscopic scale and thereby is uniquely suited to probe the local effects of perovskite materials and devices. The fundamental principles, alternative operation modes, and development of C‐AFM are comprehensively reviewed, and applications in perovskite solar cells (PSCs) for electronic transport behavior, ion migration and hysteresis, ferroelectric polarization, and facet orientation investigation are discussed. A comprehensive understanding and summary of up‐to‐date applications in PSCs is beneficial to further fully exploit the potential of such an emerging technique, so as to provide a novel and effective approach for perovskite materials analysis.

A steric engineering strategy to impede ion migration in perovskite thin films is demonstrated where ion migration is effectively hindered by localized lattice distortions induced by incorporation of oversized A site cations. The steric engineering approach improves the operational lifetime of perovskite solar cells by more than nine‐fold from 222 h to 2011 h.

Abstract

The operational instability of perovskite solar cells (PSCs) is known to mainly originate from the migration of ionic species (or charged defects) under a potential gradient. Compositional engineering of the “A” site cation of the ABX₃ perovskite structure has been shown to be an effective route to improve the stability of PSCs. Here, the effect of size‐mismatch‐induced lattice distortions on the ion migration energetics and operational stability of PSCs is investigated. It is observed that the size mismatch of the mixed “A” site composition films and devices leads to a steric effect to impede the migration pathways of ions to increase the activation energy of ion migration, which is demonstrated through multiple theoretical and experimental evidence. Consequently, the mixed composition devices exhibit significantly improved thermal stability under continuous heating at 85 °C and operational stability under continuous 1 sun illumination, with an extrapolated lifetime of 2011 h, compared to the 222 h of the reference device.

Controlling the crystallization of organic–inorganic hybrid perovskite is of vital importance to achieve high performing perovskite solar cells. However, for the printable mesoscopic perovskite solar cells, it is difficult to study the crystallization mechanism of perovskite owing to the complicated mesoporous structure. In article number https://doi.org/10.1002/aenm.2019030921903092, Yue Hu and co‐workers develop a solvent evaporation‐controlled crystallization method to achieve ideal crystallization in the mesoscopic structure.

Efficient vacuum‐assisted growth control (VAGC) allows growing micron‐sized and pinhole‐free low bandgap (E _G ≈ 1.27 eV) perovskite thin‐films for fabrication of efficient low‐bandgap perovskite solar cells. This efficient low‐bandgap perovskite solar cells enable achieving efficient all‐perovskite tandem solar cells. VAGC exhibits promising reproducibility and potential in larger active‐area solar cells up to 1 cm². More details can be found in article number https://doi.org/10.1002/aenm.2019025831902583 by Bahram Abdollahi Nejand, Ulrich W. Paetzold, and co‐workers.