Interfacial electronic coupling and band alignment of P3HT and exfoliated black phosphorous van der Waals heterojunctions

Abstract

The band alignment and the interfacial electronic coupling of van der Waals heterojunctions formed by the Poly[3-hexylthiophene-2,5-diyl] (P3HT) semiconductor polymer and the mechanically exfoliated black phosphorous (BP) multilayers were investigated using different spectroscopies techniques. The energy band alignment was assessed using Ultraviolet (UPS) and X-ray (XPS) photoelectron spectroscopies. The result of this analysis shows that the P3HT-BP interface presents a type I band alignment with conduction band minimum and the valence band maximum located in the BP layer. A valence band offset of 0.45 eV and a conduction band offset of 1.25 eV parameters were found. Near-Edge X-ray Absorption Fine Structure (NEXAFS) and resonant Auger (RAS) synchrotron-based spectroscopies were used to investigate the interfacial electronic coupling between BP and P3HT. Interfacial charge transfer times obtained from core hole clock approach and using the S1s core–hole lifetime as a reference time were used as quantitative parameters to measure the degree of electronic coupling. We found that the π*(SC) electronic state is the faster electron delocalization pathway from the P3HT to the BP conduction band and therefore there is a strong electronic coupling between these states. This result was supported from density functional theoretical calculations.