Unveiling the degraded electron durability in reduced-dimensional perovskites.

The operational stability of reduced-dimensional metal halide perovskites (RD-MHPs) lags far behind the practical requirements for future high-definition displays. Thereinto, the electron durability of RD-MHPs plays a critical role in stable LEDs during continuous operation, however, it still lacks adequate research and a deep understanding. Herein, the electron durability and deterioration mechanism of phenethylammonium (PEA)-modified RD-MHPs are systematically conducted through an photoelectron spectroscopy technique by implementing tunable electron-beam radiation to simulate device operation.

Unraveling the Hole-Transport-Layer-Manipulated Carrier Transfer Dynamics in Perovskite Light-Emitting Diodes.

Charge transfer dynamics is decisive for the performance of perovskite light emitting diodes (PeLEDs), and deep insight into the charge transfer process inside the working device is indispensable. Here, the influence of the hole transport layer on charge transport and recombination processes in PeLEDs is investigated via impedance spectroscopy. The results demonstrate that the rational interfacial energy level alignment can improve the radiative recombination by reducing the leakage current and carrier transport resistance.

Interfacial "Anchoring Effect" Enables Efficient Large-Area Sky-Blue Perovskite Light-Emitting Diodes.

While tremendous progress has recently been made in perovskite light-emitting diodes (PeLEDs), large-area blue devices feature inferior performance due to uneven morphologies and vast defects in the solution-processed perovskite films. To alleviate these issues, a facile and reliable interface engineering scheme is reported for manipulating the crystallization of perovskite films enabled by a multifunctional molecule 2-amino-1,3-propanediol (APDO)-triggered "anchoring effect" at the grain-growth interface. Sky-blue perovskite films with large-area uniformity and low trap states are obtained, showing the distinctly improved radiative recombination and hole-transport capability.

High-Light-Tolerance PbI Boosting the Stability and Efficiency of Perovskite Solar Cells.

Excess lead iodide (PbI) plays a crucial role in passivating the defects of perovskite films and boosting the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the photolysis of PbI is easily triggered by light illumination, which accelerates the decomposition of perovskite materials and weakens the long-term stability of PSCs. Herein, the high light tolerance of lead iodide (PbI) is reported by introducing an electron-donor molecule, namely, 2-thiophenecarboxamide (2-TCAm), to strengthen the [PbX] frame.

Initiating Ullmann-like coupling of BrPy by a semimetal surface.

Intensive efforts have been devoted to surface Ullmann-like coupling in recent years, due to its appealing success towards on-surface synthesis of tailor-made nanostructures. While attentions were mostly drawn on metallic substrates, however, Ullmann dehalogenation and coupling reaction on semimetal surfaces has been seldom addressed. Herein, we demonstrate the self-assembly of 2, 7-dibromopyrene (BrPy) and the well controllable dehalogenation reaction of BrPy on the Bi(111)-Ag substrate with a combination of scanning tunnelling microscopy (STM) and density functional theory calculations (DFT).

Surface-induced phase engineering and defect passivation of perovskite nanograins for efficient red light-emitting diodes.

Organic-inorganic hybrid lead halide perovskites are potential candidates for next-generation light-emitting diodes (LEDs) in terms of tunable emission wavelengths, high electroluminescence efficiency, and excellent color purity. However, the device performance is still limited by severe non-radiative recombination losses and operational instability due to a high degree of defect states on the perovskite surface. Here, an effective surface engineering method is developed via the assistance of guanidinium iodide (GAI), which allows the formation of surface-2D heterophased perovskite nanograins and surface defect passivation due to the bonding with undercoordinated halide ions.

Long-range ordered and atomic-scale control of graphene hybridization by photocycloaddition.

Chemical reactions that convert sp to sp hybridization have been demonstrated to be a fascinating yet challenging route to functionalize graphene. So far it has not been possible to precisely control the reaction sites nor their lateral order at the atomic/molecular scale. The application prospects have been limited for reactions that require long soaking, heating, electric pulses or probe-tip press.

Hierarchically Manipulated Charge Recombination for Mitigating Energy Loss in CsPbIBr Solar Cells.

All-inorganic perovskite cesium lead iodide/bromide (CsPbIBr) is considered as a robust absorber for perovskite solar cells (PSCs) because of its excellent thermal stability that guarantees its long-term operation stability. Efficient CsPbIBr PSCs are available when obtaining low energy loss, which needs efficient charge generation, less charge recombination, and balanced charge extraction. However, numerous traps in perovskites hinder the photon-electron conversion process.

Interaction of the Cation and Vacancy in Hybrid Perovskites Induced by Light Illumination.

Mixed A-site engineering is an emerging strategy to overcome the difficulties in realizing high-quality perovskite films together with high ambient stability. Particularly, the α-FACsPbI-based hybrid perovskites have been considered as a promising candidate for solar cell applications. However, the degradation mechanism of α-FACsPbI hybrid perovskites induced by light illumination remains unclear.

Revealing the Adsorption and Decomposition of EP-PTCDI on a Cerium Oxide Surface.

Cerium oxide has constantly attracted intense attention during the past decade both in research and industry as an appealing catalyst or a noninert support for catalysts, for instance, in the water-gas shift reaction and hydrogenation of the ketone group. Herein, the cerium oxide surface has been chosen to investigate the adsorption and decomposition behaviors of the ,'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) molecule by photoelectron spectroscopy. As expected, EP-PTCDI molecules self-assemble on the cerium oxide surface comprising both trivalent and tetravalent cerium at room temperature.

Recent Progress with In Situ Characterization of Interfacial Structures under a Solid-Gas Atmosphere by HP-STM and AP-XPS.

Surface science is an interdisciplinary field involving various subjects such as physics, chemistry, materials, biology and so on, and it plays an increasingly momentous role in both fundamental research and industrial applications. Despite the encouraging progress in characterizing surface/interface nanostructures with atomic and orbital precision under ultra-high-vacuum (UHV) conditions, investigating in situ reactions/processes occurring at the surface/interface under operando conditions becomes a crucial challenge in the field of surface catalysis and surface electrochemistry. Promoted by such pressing demands, high-pressure scanning tunneling microscopy (HP-STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS), for example, have been designed to conduct measurements under operando conditions on the basis of conventional scanning tunneling microscopy (STM) and photoemission spectroscopy, which are proving to become powerful techniques to study various heterogeneous catalytic reactions on the surface.

Structural Transformation of 2,7-Dibromopyrene on Au(111) Mediated by Halogen-Bonding Motifs.

Fundamental understanding of the bonding motifs that elaborately mediate the formation of supramolecular nanostructures is essential for the rational design of stable artificial organic architectures. Herein, the structural transformation of the adsorption complex of 2, 7-dibromopyrene (Br Py) on the Au(111) surface has been investigated by scanning tunnelling microscopy combined with X-ray photoemission spectroscopy and density function theory calculations. In the initial stage of self-assembly, well ordered patterns are formed in the manner of extended supramolecular structures balanced by intermolecular halogen bonding motifs, whilst the Au(111) reconstruction is still fairly visible.

Graphene oxide as an additive to improve perovskite film crystallization and morphology for high-efficiency solar cells.

The quality of a perovskite film has a great impact on its light absorption and carrier transport, which is vital to improve high-efficiency perovskite solar cells (PSCs). Herein, it is demonstrated that graphene oxide (GO) can be used as an effective additive in the precursor solution for the preparation of high-quality solution-processed CHNHPbI (MAIPbI) films. It is evidenced by scanning electron microscopy that the size of the grains inside these films not only increases but also becomes more uniform after the introduction of an optimized amount of 1 vol% GO.

Interfacial electronic structures revealed at the rubrene/CHNHPbI interface.

The electronic structures of rubrene films deposited on CHNHPbI perovskite have been investigated using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). It was found that rubrene molecules interacted weakly with the perovskite substrate. Due to charge redistribution at their interface, a downward 'band bending'-like energy shift of ∼0.