Flexible perovskite solar cells (f‐PSCs) have attracted great attention due to their promising commercial prospects. However, the performance of f‐PSCs is generally worse than that of their rigid counterparts. Herein, it is found that the unsatisfactory performance of planar heterojunction (PHJ) f‐PSCs can be attributed to the undesirable morphology of electron transport layer (ETL), which results from the rough surface of the flexible substrate. Precise control over the thickness and morphology of ETL tin dioxide (SnO2) not only reduces the reflectance of the indium tin oxide (ITO) on polyethylene 2,6‐naphthalate (PEN) substrate and enhances photon collection, but also decreases the trap‐state densities of perovskite films and the charge transfer resistance, leading to a great enhancement of device performance. Consequently, the f‐PSCs, with a structure of PEN/ITO/SnO2/perovskite/Spiro‐OMeTAD/Ag, exhibit a power conversion efficiency (PCE) up to 19.51% and a steady output of 19.01%. Furthermore, the f‐PSCs show a robust bending resistance and maintain about 95% of initial PCE after 6000 bending cycles at a bending radius of 8 mm, and they present an outstanding long‐term stability and retain about 90% of the initial performance after >1000 h storage in air (10% relative humidity) without encapsulation.

Highly efficient CsPbI2Br planar heterojunction (PHJ) perovskite solar cells (PSCs) with a structure of ITO/SnO2/CsPbI2Br/Spiro-OMeTAD/Ag are fabricated via a low-temperature solution process. A flash annealing technique is used to produce high-quality CsPbI2Br perovskite films with high density and uniformity, as well as highly crystallized CsPbI2Br films. These CsPbI2Br films are used as the light-harvesting layer in PHJ PSC devices using SnO2 as the electron transport layer and Spiro-OMeTAD as the hole transport layer. Based on the measurement of the energy levels via ultraviolet photoelectron spectroscopy, it indicates that there is a very good interfacial band alignment between SnO2 and CsPbI2Br, supporting the efficient electron extraction from CsPbI2Br to SnO2. Thus, simple structural CsPbI2Br PHJ PSCs with power conversion efficiencies (PCEs) up to 13.09% are achieved, which is comparable to the highest reported PCEs for all-inorganic PHJ PSCs. The findings show that the PHJ device architecture, instead of a mesoporous structure, can be used to fabricate highly efficient inorganic PSCs with a simple structure, offering the advantages of matching well the low-cost, high-throughout roll-to-roll printing process.

The origin of Urbach energy (E U ) in organic semiconductors and its effect on photovoltaic properties remain a topic of intense interest. In this letter, we demonstrate quantitative information on the E U value in emerging Y-series molecules by an in-depth analysis of the line shape of the temperature-dependent quantum efficiency spectra. We found that the static disorder (E U (0)), which is dominated by the conformational uniformity in Y-series acceptors, contributes 10−25 meV to the total Urbach energy. Particularly, this static contribution in organic solar cells (OSCs) is much higher than those (E U (0) ≈ 3−6 meV) in inorganic/hybrid counterparts, such as CH 3 NH 3 PbI 3 perovskite, crystalline silicon (c-Si), gallium nitride (GaN), indium phosphide (InP), and gallium arsenide (GaAs). More importantly, we establish clear correlations between the static disorder and photovoltaic performance and open-circuit voltage loss. These results suggest that suppressing the static disorder via rational molecular design is clearly a path for achieving higher performance.

Silver/copper monohalides exhibit multiferroicity with coupled ferroelasticity/ferroelectricity, high cohesive energies and low cleavage energies of multilayers.

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The near-infrared (NIR) absorbing fused-ring electron acceptor, COi8DFIC, has demonstrated very good photovoltaic performance when combined with PTB7-Th as a donor in binary organic solar cells (OSCs). In this work, the NIR acceptor was added to state-of-the-art PBDBT-2F:IT4F-based solar cells as a third component, leading to (i) an efficiency increase of the ternary devices compared to the binary solar cells in the presence of the highly crystalline COi8DFIC acceptor and (ii) much-improved photostability under 1-sun illumination. The electron transport properties were investigated and revealed the origin of the enhanced device performance. Compared to the binary cells, the optimized ternary PBDBT-2F:COi8DFIC:IT4F blends exhibit improved electron transport properties in the presence of 10% COi8DFIC, which is attributed to improved COi8DFIC molecular packing. Furthermore, transient absorption spectroscopy revealed a slow recombination of charge carriers in the ternary blend. The improved electron transport properties were preserved in the ternary OSC upon aging, while in the binary devices they seriously deteriorated after simulated 1-sun illumination of 240 h. Our work demonstrates a simple approach to enhance both OSC efficiency and photostability.

It is a great challenge to process highly efficient perovskite solar cells (PSCs) under ambient conditions, which limits their potential commercialization. Herein, high‐quality triple cation mixtures Cs0.21FA0.56MA0.23(I0.98Br0.02)3 perovskite films are fabricated through two‐step solution processes via in situ substrate‐heating‐assisted deposition under ambient conditions with a relative humidity of about 40%. The in situ substrate temperature during the deposition significantly influences the grain size and compactness of lead iodide films, and therefore greatly affects the morphology, composition, and band gap of resulted perovskite films. Based on the optimization of substrate temperature and the thickness of perovskite layer, PSCs with a planar heterojunction configuration of ITO/SnO2/perovskite/Spiro‐OMeTAD/Ag are fabricated, which deliver a power conversion efficiency up to 18.38%. These results suggest that high‐performance PSCs can be fabricated under ambient conditions instead of an inert environment, providing a fundamental step for accelerating PSC commercialization.

Superhalogens are nanoclusters with high electron affinities, exhibiting behavior similar to that of halogens. Their dimerization yields nonpolar symmetrical clusters, akin to diatomic halogen molecules, and they are unstable in the condensed phase in the absence of charge-compensating cations. Herein, we provide ab initio evidence that SbCl 4 superhalogen is an exception: its dimerization yields a polar cluster that can be viewed as a quasi-bonded [SbCl 5 ] δ− and [SbCl 3 ] δ+ Lewis acid−base cluster. The symmetry breaking arises from the valence stratification of Sb into Sb 5+ and Sb 3+ as well as their lone pair electrons. When assembled, SbCl 4 clusters form a supercrystal that is thermodynamically stable up to 600 K, with the unique bonding feature of Sb 2 Cl 8 prevailing in the bulk phase. Combination of mixed valence and lone pair electrons leads to electric polarizations along all directions, generating a type of unconventional multimode ferroelectricity in which three different modes of ferroelectricity with distinct magnitudes and Curie temperature are revealed.