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The ratio of Sn2+ to Sn4+ plays an essential role in influencing the characteristics of SnO2 film, which is commonly used in the normal structure of perovskite solar cells (PSCs). It is identified that different sequences of addition lead to varying concentrations of Sn2+ and Sn4+ within the SnO2 film. Through this strategic approach, an enhanced SnO2 film with improved electron transport capabilities, a smoother surface texture, and more suitable energy levels are successfully engineered. Consequently, the efficiency of PSCs has seen a notable increase from 22.58% for the control device to 24.16% for the target PSC. Furthermore, PSCs utilizing the optimized SnO2 have demonstrated superior long‐term environmental stability when compared to the control devices. Specifically, PSCs incorporating optimized SnO2 expose to approximately 30% humidity in ambient air for 41 days without encapsulation retain 87% of their initial efficiency. In contrast, the control devices under the same conditions only maintain 77% of their original value. [ABSTRACT FROM AUTHOR]

Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is 26.1%, their stability is still a roadblock for large‐scale commercialization. In the initial density‐functional theory research, it is shown that the most damaging type of defect that destroys device performance is undercoordinated Pb2+ on the surface of the perovskite thin film. An ultraviolet‐absorbent material, 2‐hydroxybenzophenone (HBP), is utilized to specifically passivate this type of defect. In theoretical studies, it is shown that it effectively binds to the undercoordinated Pb2+ via its –C═O group. It also passivates I−‐related defects by forming a hydrogen bond using its –OH group, resulting in decreased trap density and hence prolonged carrier lifetime. The HBP can absorb ultraviolet irradiation, leading to much‐reduced UV degradation; its hydrophobic benzene rings protect the perovskite from moisture permeation. As a result, the constructed device reaches a high PCE of 16.39% with superior stability. The bare device maintains 80.4% of its initial PCE after exposure to ambient air for 792 h. In comparison, the control device without HBP retains only 63.2% of its initial efficiency. Under UV irradiation (80 mW cm−2, 365 nm) for 13 h, the former retains 77.9% of its initial PCE while the control device lost 52% of its initial value. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (FPSCs) with excellent recoverability show a wide range of potential applications in portable power sources. The recoverability of FPSCs requires outstanding bendability of each functional layer, including the flexible substrates, electrodes, perovskite light absorbers, and charge transport materials. This review highlights the recent progress and practical applications of high‐recoverability FPSCs, and illustrates the routes toward improvement of the recoverability and environmental stability through the choice of flexible substrates and the preparation of high‐quality perovskite films, as well as the optimization of charge‐selective contacts. In addition, we explore the intrinsic properties of each functional layer from the physical perspective and analyze how to select suitable functional layers. Additionally, some effective strategies are summarized, including material modification engineering of selective contacts, additives and interface engineering of interlayers, which can release mechanical stress and increase the power‐conversion efficiency (PCE) and recoverability of the FPSCs. The challenges of making high‐performance FPSCs with long‐term stability and high recoverability are discussed. Finally, future applications and perspectives for FPSCs are discussed, aiming to promote more extensive commercialization processes for lightweight and durable FPSCs. [ABSTRACT FROM AUTHOR]

The defects within perovskite films are the fatal roadblock limiting the performance of perovskite solar cells (PSCs). Herein, we develop a patching strategy to obtain high‐quality perovskite film using bifunctional trifluorophenylacetic acid (TFPA). Theoretical calculation and experiments reveal that the –COOH groups in TFPA effectively passivate the deep‐energy‐level defects of perovskite by combining with Pb clusters on the perovskite grain surfaces to enhance the efficiency of PSCs, and hydrophobic benzene groups containing fluorine in TFPA are exposed to improve the stability of PSCs. The power conversion efficiency (PCE) of PSCs with TFPA is enhanced from 22.95% to 24.56%. Most importantly, we successfully fabricated flexible PSCs using TFPA with the high PCE of 22.65%. The devices with TFPA maintain 93.22% of the initial efficiency MPP under continuous irradiation for 10.5 h, while the devices without TFPA only retain 82.22% of the initial efficiency under the same conditions for just 5 h. Meanwhile, the unsealed devices with TFPA hold 93.59% of the initial efficiency when stored in air for 3912 h. [ABSTRACT FROM AUTHOR]

Interlayer excitons (IXs) are demonstrated in two‐dimensional (2D) perovskite/transition‐metal dichalcogenide (TMD) heterostructures regardless of the lattice match, momentum mismatch, and thermal annealing processes. The broad selection of 2D perovskites and TMDs together with the robust interlayer coupling between constituent layers make 2D perovskite/TMD heterostructures an attractive platform for studying IXs. However, studies on IXs in 2D perovskite/TMD heterostructures are still in their infancy, and how the organic cation affects the IXs in 2D perovskite/TMD heterostructures remains elusive. Herein, this article reports on IXs emission from heterostructures consisting of monolayer WSe2 and 2D perovskites with different organic cations. Notably, by temperature‐dependent photoluminescence studies on (EA)2PbI4/WSe2 and (PEA)2PbI4/WSe2 heterostructures (EA = ethylamine and PEA = phenylethylammonium), it is found that the organic cations of 2D perovskites can effectively change the exciton binding energy of the IXs and thus the emission peak of the IXs. The observed difference can be ascribed to the significant dielectric constant difference between their organic cations. Furthermore, the change in the organic cations can also affect the dipole–dipole interaction and lifetime of IXs. The findings provide critical insights into the 2D perovskite/TMD heterointerfaces and also open up new opportunities for exploiting tunable exciton devices based on IXs. [ABSTRACT FROM AUTHOR]

2D/3D bilayer perovskite synthesized using sequential deposition methods has shown effectiveness in enhancing the stability of perovskite solar devices. However, these approaches present several limitations such as uncontrolled chemical processes, disordered interfacial states, and microscale heterogeneities that can chemically, structurally, and electronically compromise the performance of solar modules. Here, this work demonstrates an emulsion‐based self‐assembly approach using natural lipid biomolecules in a nonionic solution system to form a 0D/3D bilayer structure. The new capping layer is composed of 0D‐entity nanoparticles of perovskite encapsulated by a hydrophobic lipid membrane, analogous to a cell structure, formed through a molecular self‐assembly process. This 0D layer provides a strong water repellent characteristics, optimum interface microstructure, and excellent homogeneity that drives significant enhancement in stability. Solar modules with a large active area of 70 cm2 fabricated using films comprising of 0D/3D bilayer structure are found to show consistent efficiency of >19% for 2800 h of continuous illumination in the air (60% relative humidity). This emulsion‐based self‐assembly approach is expected to have a transformative impact on the design and development of stable perovskite‐based devices. [ABSTRACT FROM AUTHOR]

Solution‐processable organic–inorganic hybrid perovskite materials have been applied to a variety of optoelectronic devices due to its long exciton lifetime and small binding energy. It has emerged as promising front‐runners for next‐generation non‐volatile flash photomemory devices. However, the effect of crystal orientation of perovskite on the performance of photomemory still has not fully developed. Herein, non‐volatile flash photomemory with quasi‐2D perovskite/polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) as photoactive floating‐gate and p‐type semiconductor poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as the chare‐transporting layer is successfully demonstrated. By adding phenylethylammonium bromide (PEABr) in formamidinium lead bromide perovskite (FAPbBr3), the crystal orientation of quasi‐2D perovskite is highly improved, which results in raised charge transfer efficiency from 76% to 90% compared to the pure FAPbBr3. Furthermore, ON/OFF current ratio of 104, low photo‐programming time of 5 ms under light intensity of 0.85 mW cm−2, charge transfer rate of 0.063 ns−1, and data storage capacity of over 7 bits (128 levels) in one cell can be achieved. In addition, the correlation between photo‐responsive current and photoluminescence (PL) is first examined by in operando PL measurement, which provides a new platform to explore the charge transfer process in photomemory. [ABSTRACT FROM AUTHOR]

Emulation of photonic synapses through photo‐recordable devices has aroused tremendous discussion owing to the low energy consumption, high parallel, and fault‐tolerance in artificial neuromorphic networks. Nonvolatile flash‐type photomemory with short photo‐programming time, long‐term storage, and linear plasticity becomes the most promising candidate. Nevertheless, the systematic studies of mechanism behind the charge transfer process in photomemory are limited. Herein, the physical properties of APbBr3 perovskite quantum dots (PQDs) on the photoresponsive characteristics of derived poly(3‐hexylthiophene‐2,5‐diyl) (P3HT)/PQDs‐based photomemory through facile A‐site substitution approach are explored. Benefitting from the lowest valance band maximum and longest exciton lifetime of FAPbBr3 quantum dot (FA‐QDs), P3HT/FA‐QDs‐derived photomemory not only exhibits shortest photoresponsive characteristic time compared to FA0.5Cs0.5PbBr3 quantum dots (Mix‐QDs) and CsPbBr3 quantum dots (Cs‐QDs) but also displays excellent ON/OFF current ratio of 2.2 upon an extremely short illumination duration of 1 ms. Moreover, the device not only achieves linear plasticity of synapses by optical potentiation and electric depression, but also successfully emulates the features of photon synaptic such as pair‐pulse facilitation, long‐term plasticity, and multiple spike‐dependent plasticity and exhibits extremely low energy consumption of 3 × 10−17 J per synaptic event. [ABSTRACT FROM AUTHOR]

Perovskite photovoltaics (PV) is an emerging thin‐film solar energy technology that is advantageous over the currently dominant crystalline silicon PV in terms of its adjustable bandgap with sub‐bandgap transparency, potential flexibility, and more rapid continuous roll‐to‐roll manufacturing, showing promise for unique niche applications. Herein, methylammioun lead tribromide (MAPbBr3) is utilized in a semitransparent flexible solar cell with a transparent electrode using a sandwiched MoO3/Au/MoO3 (MAM) multilayer to harvest around 80% of the visible light region. Through design of the thickness of the MAM multilayer, the reflected light loss is significantly reduced, thereby improving the light transmittance in the visible light region to maximize the photosynthetic yield. The semitransparent flexible device exhibits a power conversion efficiency (PCE) of 7.67% (the highest efficiency of MAPbBr3‐based semitransparent flexible devices), and the opaque rigid MAPbBr3 solar cell shows a PCE of 9.73% with a high open‐circuit voltage of 1.629 V. Optical measurement demonstrates that the flexible cell without metal electrode shows over 77% transparency in the 540–1100 nm range, whereas the overall semitransparent cell shows an average transmittance of 60% in the 540–760 nm range, which is perfect for greenhouse vegetation to not only act as protective coverage but also provide practical output power. [ABSTRACT FROM AUTHOR]

Even though ZnO is commonly used as the ETL in the perovskite solar cell (PSC), the reactivity of perovskite deposited thereupon limits its performance. Herein, an ethylene diamine tetraacetic acid‐complexed ZnO (E‐ZnO) is successfully developed as a significantly improved electron selective layer (ESLs) in perovskite device. It is found that E‐ZnO exhibits higher electron mobility and better matched energy level with perovskite compared to ZnO. In addition, in order to eliminate the proton transfer reaction at the ZnO/perovskite interface, a high quality perovskite film fabrication process that requires neither annealing nor antisolvent is developed. By taking advantages of both E‐ZnO and the new process, the highest efficiency of 20.39% is obtained for PSCs based on E‐ZnO. Moreover, the efficiency of unencapsulated PSCs with E‐ZnO retains 95% of its initial value exposed in an ambient atmosphere after 3604 h. This work provides a feasible path toward high performance of PSCs, and it is believed that the present work will facilitate transition of perovskite photovoltaics in flexible and tandem devices since the annealing‐ and antisolvent‐free technology. [ABSTRACT FROM AUTHOR]

Surface defects have been a key constraint for perovskite photovoltaics. Herein, 1,3‐dimethyl‐3‐imidazolium hexafluorophosphate (DMIMPF6) ionic liquid (IL) is adopted to passivate the surface of a formamidinium‐cesium lead iodide perovskite (Cs0.08FA0.92PbI3) and also reduce the energy barrier between the perovskite and hole transport layer. Theoretical simulations and experimental results demonstrate that Pb‐cluster and Pb‐I antisite defects can be effectively passivated by [DMIM]+ bonding with the Pb2+ ion on the perovskite surface, leading to significantly suppressed non‐radiative recombination. As a result, the solar cell efficiency was increased to 23.25 % from 21.09 %. Meanwhile, the DMIMPF6‐treated perovskite device demonstrated long‐term stability because the hydrophobic DMIMPF6 layer blocked moisture permeation. [ABSTRACT FROM AUTHOR]

With the power conversion efficiencies of perovskite solar cells (PSCs) exceeding 25%, the PSCs are a step closer to initial industrialization. Prior to transferring from laboratory fabrication to industrial manufacturing, issues such as scalability, material cost, and production line compatibility that significantly impact the manufacturing remain to be addressed. Here, breakthroughs on all these fronts are reported. Carbon‐based PSCs with architecture fluorine doped tin oxide (FTO)/electron transport layer/perovskite/carbon, that eliminate the need for the hole transport layer and noble metal electrode, provide ultralow‐cost configuration. This PSC architecture is manufactured using a scalable and industrially compatible electrospray (ES) technique, which enables continuous printing of all the cell layers. The ES deposited electron transport layer and perovskite layer exhibit properties comparable to that of the laboratory‐scale spin coating method. The ES deposited carbon electrode layer exhibits superior conductivity and interfacial microstructure in comparison to films synthesized using the conventional doctor blading technique. As a result, the fully ES printed carbon‐based PSCs show a record 14.41% power conversion efficiency, rivaling the state‐of‐the‐art hole transporter‐free PSCs. These results will immediately have an impact on the scalable production of PSCs. [ABSTRACT FROM AUTHOR]

As the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is increased to as high over 25%, it becomes pre‐eminent to study a scalable process with wide processing window to fabricate large‐area uniform perovskite films with good light‐trapping performance. A stable and uniform intermediate‐state complex film is obtained by using tetramethylene sulfoxide (TMSO), which extends the annealing window to as long as 20 min, promotes the formation of a high‐quality perovskite film with larger grains (over 400 nm) and spontaneously forms the surface texture to result in an improved fill factor and open‐circuit voltage (Voc). Moreover, the superior surface texture significantly increases the long‐wavelength response, leading to an improved short‐circuit current density (Jsc). As a result, the maximum PCE of 21.14% is achieved based on a simple planar cell structure without any interface passivation. Moreover, a large area module with active area of 6.75 cm2 is assembled using the optimized TMSO process, showing efficiency as high as 16.57%. The study paves the way to the rational design of highly efficient PSCs for potential scaled‐up production. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells have attracted widespread research effort because of their potential in portable electronics. The efficiency has exceeded 18 % owing to the high‐quality perovskite film achieved by various low‐temperature fabrication methods and matching of the interface and electrode materials. This Review focuses on recent progress in flexible perovskite solar cells concerning low‐temperature fabrication methods to improve the properties of perovskite films, such as full coverage, uniform morphology, and good crystallinity; demonstrated interface layers used in flexible perovskite solar cells, considering key figures‐of‐merit such as high transmittance, high carrier mobility, suitable band gap, and easy fabrication via low‐temperature methods; flexible transparent electrode materials developed to enhance the mechanical stability of the devices; mechanical and long‐term environmental stability; an outlook of flexible perovskite solar cells in portable electronic devices; and perspectives of commercialization for flexible perovskite solar cells based on cost. Flexible perovskite solar cells have attracted significant attention owing to their promising potential in practical applications. This Review discusses the prerequisite conditions for flexible perovskite solar cells, provides an outlook of flexible perovskite devices in portable electronic products, and estimates their production cost by roll‐to‐roll vacuum deposition for commercialization. [ABSTRACT FROM AUTHOR]

Oxygen selective membranes with enhanced oxygen permeability and CO2 resistance are highly required in sustainable clean energy generation technologies. Here, we present novel, cobalt-free, SrFe1− xTa xO3− δ ( x=0, 0.025, 0.05, 0.1, 0.2) perovskite membranes. Ta-doping induced lattice structure progression from orthorhombic ( x=0) to cubic ( x=0.05). SrFe0.95Ta0.05O3− δ (SFT0.05) showed the highest oxygen flux rates reaching 0.85 mL min−1 cm−2 at 950 °C on a 1.0 mm-thick membrane. Surface decoration can increase the permeation rate further. Ta inclusion within the perovskite lattice of SrFeO3− δ (SF) enhanced the CO2 resistance of the membranes significantly as evidenced by the absence of the carbonate functional groups on the FTIR spectrum when exposed to CO2 atmosphere at 850 °C. The CO2 resistance of Ta-doped SF compounds correlates with the lower basicity and the higher binding energy for the lattice oxygen. SFT0.05 demonstrated high stability during long-term permeation tests under 10 % CO2 atmosphere. [ABSTRACT FROM AUTHOR]

Multijunction/tandem solar cells have naturally attracted great attention because they are not subject to the Shockley–Queisser limit. Perovskite solar cells are ideal candidates for the top cell in multijunction/tandem devices due to the high power conversion efficiency (PCE) and relatively low voltage loss. Herein, sandwiched gold nanomesh between MoO3 layers is designed as a transparent electrode. The large surface tension of MoO3 effectively improves wettability for gold, resulting in Frank–van der Merwe growth to produce an ultrathin gold nanomesh layer, which guarantees not only excellent conductivity but also great optical transparency, which is particularly important for a multijunction/tandem solar cell. The top MoO3 layer reduces the reflection at the gold layer to further increase light transmission. As a result, the semitransparent perovskite cell shows an 18.3% efficiency, the highest reported for this type of device. When the semitransparent perovskite device is mechanically stacked with a heterojunction silicon solar cell of 23.3% PCE, it yields a combined efficiency of 27.0%, higher than those of both the sub‐cells. This breakthrough in elevating the efficiency of semitransparent and multijunction/tandem devices can help to break the Shockley–Queisser limit. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of inverted perovskite solar cells (i‐PSCs) is lower than that of the normal structures. The low efficiency is mainly ascribed to the inferior properties of commonly used [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) electron transport layers (ETLs) such as complexity in achieving high‐quality films, low electron mobility, imperfect energy level for electron extraction, and large electron capture region. Herein, the bulk heterojunction (BHJ) ETLs composed of PCBM and polymers are developed. The electron mobility of the BHJ film is enhanced by more than three times compared with PCBM, leading to efficient electron extraction. The electron capture region of the BHJ film decreases to 1.20 × 10−18 from 3.70 × 10−17 cm−3 for PCBM due to increased relative permittivity, which reduces the trap‐assistant recombination at the interface. Meanwhile, the devices with BHJ exhibit good stability regardless of illumination and dark storage conditions owing to the more hydrophobic BHJ films and full coverage of perovskite surface, which effectively prevent the moisture permeation into the perovskite devices. It is believed that this breakthrough provides a suitable approach to improve the efficiency and stability of i‐PSCs. [ABSTRACT FROM AUTHOR]

Up to now, multijunction cell design is the only successful way demonstrated to overcome the Shockley–Quiesser limit for single solar cells. Perovskite materials have been attracting ever‐increasing attention owing to their large absorption coefficient, tunable bandgap, low cost, and easy fabrication process. With their rapidly increased power conversion efficiency, organic–inorganic metal halide perovskite‐based solar cells have demonstrated themselves as the most promising candidates for next‐generation photovoltaic applications. In fact, it is a dream come true for researchers to finally find a perfect top‐cell candidate in tandem device design in commercially developed solar cells like single‐crystalline silicon and CIGS cells used as the bottom component cells. Here, the recent progress of multijunction solar cells is reviewed, including perovskite/silicon, perovskite/CIGS, perovskite/perovskite, and perovskite/polymer multijunction cells. In addition, some perspectives on using these solar cells in emerging markets such as in portable devices, Internet of Things, etc., as well as an outlook for perovskite‐based multijunction solar cells are discussed. Multijunction solar cells have demonstrated the capability to overcome the Shockley–Quiesser limit for sing‐junction solar cells. This work reviews the recent progress of the different types of multijunction solar cells based on perovskites, conceives a triple‐junction solar cell, and outlooks their applications in emerging markets such as in portable electrons, Internet of Things, etc. [ABSTRACT FROM AUTHOR]

In article number 1804419, Congcong Wu, Shashank Priya, and co‐workers develope a dual‐functional PMMA‐fullerene complex, where the fullerene C60 dwells in the caves of the PMMA polymer chain. The PMMA‐fullerene complex is incorporated into the perovskite layer, which resides along the grain boundary of the perovskites. The fullerene reduces the charge carrier recombination and the PMMA polymer improves the stability of the perovskite solar cell. [ABSTRACT FROM AUTHOR]