BN-Embedded Cycloarenes: One-Pot Borylation Synthesis, Photoelectric Properties, and Application in Perovskite Solar Cells

Abstract

<p>Incorporating heteroatoms, such as nitrogen, oxygen,and/or sulfuratoms, into cycloarenes can effectively regulate their molecular geometriesand (opto)electronic properties. However, the rarity of cycloarenesand heterocycloarenes limits the further exploitation of their applications.Herein, we designed and synthesized the first examples of boron andnitrogen (BN)-doped cycloarenes (BN-C1 and BN-C2) via one-pot intramolecular electrophilic borylation of imine-basedmacrocycles. BN-C2 adopts a bowl-shaped conformation,while BN-C1 possesses a planar geometry. Accordingly,the solubility of BN-C2 was significantly improved byreplacing two hexagons in BN-C1 with two N-pentagons,due to the creation of distortions away from planarity. Various experimentsand theoretical calculations were carried out for heterocycloarenes BN-C1 and BN-C2, demonstrating that the incorporatedBN bonds diminish the aromaticity of 1,2-azaborine units and theiradjacent benzenoid rings but preserve the dominant aromatic propertiesof pristine kekulene. Importantly, when two additional electron-richnitrogen atoms were introduced, the highest occupied molecular orbitalenergy level of BN-C2 was elaborately lifted comparedwith that of BN-C1. As a result, the energy-level alignmentof BN-C2 with the work function of the anode and theperovskite layer was suitable. Therefore, for the first time, heterocycloarene(BN-C2) was explored as a hole-transporting layer ininverted perovskite solar cell devices, in which the power conversionefficiency reached 14.4%.</p>