Tris(4-(1-phenyl-1H-benzo[d]imidazole)phenyl)phosphine oxide for enhanced mobility and restricted traps in photovoltaic interlayers

Abstract

Among small molecule organic materials, tris(4-(1-phenyl-1H-benzo[d]imidazole)phenyl)phosphine oxide (TIPO) and 2,4,6-tris(4-(1-phenyl-1H-benzo[d]imidazol)phenyl)-1,3,5-triazine were newly synthesised and introduced into an n-type interlayer in planar perovskite solar cells for effective electron transport. The small molecule materials contain phenyl benzimidazole, which is combined with a phosphine oxide core or a triazine ring core and contributes to the improvement of charge extraction and stability. As the constituent molecules—phosphine oxide and benzimidazole—have strong polarity properties and π-electrons, the molecules induce passivating defects towards improving charge transport and flattening the surface morphology. Moreover, the stability of the device was increased due to the introduction of the TIPO material as the passivation and protection layer. In this electron extraction analysis, electrical resistance and surface morphology investigations were carried out via space charge-limited current, photoluminescence, impedance, and atomic force microscopy analyses.