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To activate methane at low or medium temperatures is a difficult task and a pre-requisite for the conversion of this light alkane into high value chemicals. Herein, we report the...

Structural, mechanical, electronic properties, and stability of boron nitride (BN) in Pnma structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code, and the calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew–Burke–Ernzerhof. This BN, called Pnma-BN, contains four boron atoms and four nitrogen atoms buckled through sp3-hybridized bonds in an orthorhombic symmetry unit cell with Space group of Pnma. Pnma-BN is energetically stable, mechanically stable, and dynamically stable at ambient pressure and high pressure. The calculated Pugh ratio and Poisson’s ratio revealed that Pnma-BN is brittle, and Pnma-BN is found to turn brittle to ductile (~94 GPa) in this pressure range. It shows a higher mechanical anisotropy in Poisson’s ratio, shear modulus, Young’s modulus, and the universal elastic anisotropy index AU. Band structure calculations indicate that Pnma-BN is an insulator with indirect band gap of 7.18 eV. The most extraordinary thing is that the band gap increases first and then decreases with the increase of pressure from 0 to 60 GPa, and from 60 to 100 GPa, the band gap increases first and then decreases again.

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Chemical additive engineering is reported to be a simple yet effective approach to passivate shallow defects at the surface and grain boundaries, restrict nonradiative recombination losses, and further enhance the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, we successfully introduce a small organic molecule 3,5-bis(trifluoromethyl)benzoic acid (6FBzA) into an antisolvent as a shallow defect passivator for perovskite films. The Pb 2+ defects at the surface are greatly healed due to the coordination interaction of carbonyl and fluorine groups of 6FBzA with Pb 2+ . Consequently, the trap-assisted nonradiative recombination is effectively suppressed, as well as the interfacial charge extraction and transfer is significantly enhanced. As a result, the 6FBzA-treated PSC obtains a champion PCE of 21.09% with negligible hysteresis, which is obviously superior to the reference device (18.45%). Furthermore, on account of the high hydrophobicity of 6FBzA, the unencapsulated 6FBzA-treated device exhibits a good long-term stability, maintaining 82% of its initial PCE at a relative humidity of 30−40% in ambient air after 1800 h of aging.

The surface and boundary defects present in the perovskite film are reported to be nonradiative recombination and degradation centers, restricting further improvement of the power conversion efficiency (PCE) and long-term stability of perovskite solar cells. To address this problem, herein, we introduce a fluorine-substituted small molecular material 2FBTA-1 as a bifunctional buffer layer to efficiently passivate the surface defects of perovskite and tune the energy level alignment between the perovskite/2,2′,7,7′-tetrakis(N,N-di-(pmethoxyphenyl)amino)-9,9′-spirobifluorene (Spiro-OMeTAD) interface. X-ray photoelectron spectroscopy shows that with the insertion of 2FBTA-1 between perovskite and Spiro-OMeTAD, the metallic Pb 0 defects and uncoordinated Pb 2+ defects are well restricted. Consequently, the average PCE is distinctly improved from 18.4 ± 0.51 to 20.3 ± 0.40%. Moreover, the long-term stability of unencapsulated devices with 2FBTA-1 treatment under ambient conditions (relative humidity 40−60%) is effectively enhanced, retaining 87% of the initial efficiency after storage for 500 h.

An interesting physical phenomenon, electroluminescence, that was originally observed with a hydrocarbon molecule has recently been developed into highly efficient organic light-emitting devices. These modern devices have evolved through the development of multi-element molecular materials for specific roles, and hydrocarbon devices have been left unexplored. In this study, we report an efficient organic light-emitting device composed solely of hydrocarbon materials. The electroluminescence was achieved in the blue region by efficient fluorescence and charge recombination within a simple single-layer architecture of macrocyclic aromatic hydrocarbons. This study may stimulate further studies on hydrocarbons to uncover their full potential as electronic materials.

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