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CsPbI3 perovskite is a promising light absorber in perovskite solar cells (PSCs) due to its suitable bandgap (Eg) and high chemical stability, but the perovskite phase is metastable in ambient atmosphere and prone to defect formation. To enhance phase stability and reduce defects, forming a low dimensional (LD) perovskite on CsPbI3 has proved effective. However, the energy levels for most of low‐conductivity LD perovskites are not very compatible with those of CsPbI3, which will impair charge separation and device performance. Herein, a new 1D perovskite (5‐Azaspiro[4.4]nonan‐5‐ium lead triiodide, ASNPbI3) with compatible energy levels and a large Eg is reported as a capping layer. The p‐type ASNPbI3 forms a p‐n heterojunction with n‐CsPbI3 with a staggered band alignment, considerably enhancing the carrier separation. Besides, by pre‐forming a ASNPbI3 at an intermediate stage, defects are suppressed in perovskite film. Consequently, the CsPbI3 PSCs based on carbon electrode without hole transporter (C‐PSCs) achieves a PCE of 18.34%, which is among the highest‐reported values for inorganic C‐PSCs. Furthermore, the hydrophobic ASNPbI3 capping layer has a high thermal stability that greatly enhances perovskite phase stability. Hence, the CsPbI3 C‐PSCs maintains 68% of its initial PCE after 400 h aging at 85°C in a N2 glovebox. [ABSTRACT FROM AUTHOR]

The tsunami of research on halide perovskites over the last decade is sparked by the unexpected revelation of their singular properties, creating a new field of perovskite optoelectronics with great achievements. Soon recognized is the importance of perovskite–perovskite (pe–pe) interfaced structures with coherent interfaces on account of the ease with which to tailor perovskite semiconducting properties, and the prospect to inject new functions and boost device performance. There have been prominent developments in the pe–pe interfaced structures concerning their innovative construction strategies, distinctive properties, and interesting optoelectronic applications. This article provides an overview of recent advances on the pe–pe interfaced structures with a view to informing their rational design and guiding the improvement of the derivate devices. It begins with introduction of the structures, energy levels, band alignments, and ion migration pertaining to the pe–pe interfaced structures. Next, five synthetic approaches are systematically presented. Then, theories, simulations, and characterizations of the interfaced structures are discussed. This is followed by highlighting the distinctive applications of the pe–pe interfaced structures in solar cells, detectors, and light‐emitting diodes. Finally, the review is concluded by comprehensively summing up the key points covered and pointing out promising research directions along the line for future endeavors. [ABSTRACT FROM AUTHOR]

Transition metal elements such as Ni in high oxidation states can promote oxygen evolution reaction (OER) activity, but it is difficult to prepare dispersed Ni3+ or even Ni4+ species under mild conditions. Herein, a one‐step synthesis of high‐valence nickel‐doped CeO2−x covered with FeOOH nanosheets in the presence of Ni2+/Fe3+ is reported. A series of ex situ and in situ experiments reveal the etching effect on ceria of the H+ species from the hydrolysis of Fe3+, which induces substitutional doping of Ni2+ ions into the etched sites and their further oxidation to the high‐valance Ni3+/Ni4+ by coupling to the Ce4+/Ce3+ pair in the oxygen‐vacancy‐rich CeO2−x. Concomitantly, Fe3+ is deposited on the surface of ceria as FeOOH nanosheets. The dispersed high‐valent Ni3+/Ni4+ coupled with the decorated FeOOH nanosheets on CeO2−x leads to efficient OER electrocatalysis with a low overpotential of 195 mV cm−2 at a current density of 10 mA cm−2 and a high turnover frequency (TOF) of 0.99 s−1, which, to the best of the authors' knowledge represents the best Ce‐containing OER catalyst reported to date, and comparable to other top OER catalysts. This work opens an avenue for engineering high‐valence metal ions in an oxide matrix for the OER or other oxidation reactions. [ABSTRACT FROM AUTHOR]

Abstract: Organic–inorganic hybrid perovskite solar cells (PVSCs) have become the front‐running photovoltaic technology nowadays and are expected to profoundly impact society in the near future. However, their practical applications are currently hampered by the challenges of realizing high performance and long‐term stability simultaneously. Herein, the development of inverted PVSCs is reported based on low temperature solution‐processed CuCrO2 nanocrystals as a hole‐transporting layer (HTL), to replace the extensively studied NiOx counterpart due to its suitable electronic structure and charge carrier transporting properties. A ≈45 nm thick compact CuCrO2 layer is incorporated into an inverted planar configuration of indium tin oxides (ITO)/c‐CuCrO2/perovskite/[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)/bathocuproine (BCP)/Ag, to result in the high steady‐state power conversion efficiency of 19.0% versus 17.1% for the typical low temperature solution‐processed NiOx‐based devices. More importantly, the optimized CuCrO2‐based device exhibits a much enhanced photostability than the reference device due to the greater UV light‐harvesting of the CuCrO2 layer, which can efficiently prevent the perovskite film from intense UV light exposure to avoid associated degradation. The results demonstrate the promising potential of CuCrO2 nanocrystals as an efficient HTL for realizing high‐performance and photostable inverted PVSCs. [ABSTRACT FROM AUTHOR]

Abstract: Organic‐inorganic halide perovskite materials have become a shining star in the photovoltaic field due to their unique properties, such as high absorption coefficient, optimal bandgap, and high defect tolerance, which also lead to the breathtaking increase in power conversion efficiency from 3.8% to over 22% in just seven years. Although the highest efficiency was obtained from the TiO2 mesoporous structure, there are increasing studies focusing on the planar structure device due to its processibility for large‐scale production. In particular, the planar p‐i‐n structure has attracted increasing attention on account of its tremendous advantages in, among other things, eliminating hysteresis alongside a competitive certified efficiency of over 20%. Crucial for the device performance enhancement has been the interface engineering for the past few years, especially for such planar p‐i‐n devices. The interface engineering aims to optimize device properties, such as charge transfer, defect passivation, band alignment, etc. Herein, recent progress on the interface engineering of planar p‐i‐n structure devices is reviewed. This review is mainly focused on the interface design between each layer in p‐i‐n structure devices, as well as grain boundaries, which are the interfaces between polycrystalline perovskite domains. Promising research directions are also suggested for further improvements. [ABSTRACT FROM AUTHOR]

2D halide perovskite materials have shown great advantages in terms of stability when applied in a photovoltaic device. However, the impediment of charge transport within the layered structure drags down the device performance. Here for the first time, a 3D-2D (MAPbI3-PEA2Pb2I4) graded perovskite interface is demonstrated with synergistic advantages. In addition to the significantly improved ambient stability, this graded combination modifies the interface energy level in such a way that reduces interface charge recombination, leading to an ultrahigh Voc at 1.17 V, a record for NiO-based p-i-n photovoltaic devices. Moreover, benefiting from the graded structure induced continuously upshifts energy level, the photovoltaic device attains a high Jsc of 21.80 mA cm−2 and a high fill factor of 0.78, resulting in an overall power conversion efficiency (PCE) of 19.89%. More importantly, it is showed that such a graded interface structure also suppresses ion migration in the device, accounting for its significantly enhanced thermal stability. [ABSTRACT FROM AUTHOR]

In this work, both anode and cathode interfaces of p-i-n CH3NH3PbI3 perovskite solar cells (PVSCs) are simultaneously modified to achieve large open-circuit voltage (Voc) and fill factor (FF) for high performance semitransparent PVSCs (ST-PVSCs). At the anode, modified NiO serves as an efficient hole transport layer with appropriate surface property to promote the formation of smooth perovskite film with high coverage. At the cathode, a fullerene bisadduct, C60(CH2)(Ind), with a shallow lowest unoccupied molecular orbital level, is introduced to replace the commonly used phenyl-C61-butyric acid methyl ester (PCBM) as an alternative electron transport layer in PVSCs for better energy level matching with the conduction band of the perovskite layer. Therefore, the Voc, FF and power conversion efficiency (PCE) of the PVSCs increase from 1.05 V, 0.74 and 16.2% to 1.13 V, 0.80 and 18.1% when the PCBM is replaced by C60(CH2)(Ind). With the advantages of high Voc and FF, ST-PVSCs are also fabricated using an ultrathin transparent Ag as cathode, showing an encouraging PCEs of 12.6% with corresponding average visible transmittance (AVT) over 20%. These are the highest PCEs reported for ST-PVSCs with similar AVTs paving the way for using ST-PVSCs as power generating windows. [ABSTRACT FROM AUTHOR]

Hydrogen Evolution Reaction: One-Step Controllable Synthesis of Catalytic Ni4Mo/MoOx/Cu Nanointerfaces for Highly Efficient Water Reduction (Adv. In article number 1901454, Bolong Huang, Shihe Yang, and co-workers develop a Cu-supported Ni SB 4 sb Mo nanodot on MoO SB I x i sb nanosheet as a hydrogen evolution reaction (HER) electrocatalyst based on the facile one-step electrodeposition process. This electrocatalyst displays the optimal electronic structure with the promotion of a Cu support, which leads to an ultra-low overpotential of 16 mV for HER in an alkaline environment. [Extracted from the article]