Interfacial versus Bulk Properties of Hole-Transporting Materials for Perovskite Solar Cells: Isomeric Triphenylamine-Based Enamines versus Spiro-OMeTAD

Abstract

Here,wereportonthreenewtriphenylamine-based enamines synthesizedbycondensationof anappropriateprimary amine with 2,2-diphenylacetaldehyde and characterized by experimental techniques and density functional theory (DFT) computations. Experimental results allowhighlighting attractive propertiesincludingsolid-stateionizationpotential intherangeof 5.33−5.69 eV in solid-state andholemobilities exceeding 10−3 cm2/V·s,whicharehigher than those inspiro-OMeTADat the sameelectricfields.DFT-basedanalysispoints tothepresenceof several conformers close in energy at room temperature. The newlysynthesizedhole-transportingmaterials(HTMs)wereused inperovskitesolarcellsandexhibitedperformancescomparableto that of spiro-OMeTAD.Thedevicecontainingonenewly synthesizedhole-transportingenaminewas characterizedbyapower conversionefficiencyof18.4%.Ouranalysis indicates that theperovskite−HTMinterfacedominates thepropertiesofperovskite solarcells.PLmeasurements indicatesmallerefficiencyforperovskite-to-newHTMholetransferascomparedtospiro-OMeTAD. Nevertheless, the comparablepower conversionefficiencies and simple synthesis of thenewcompoundsmake themattractive candidates forutilizationinperovskitesolarcells.