Charge transfer induced surface enhanced Raman scattering of single crystal and polycrystal perovskites

The charge transfer(CT) process plays a key role in the operation of the optoelectronic device system so a better understanding of the interfacial CT property is greatly important. In this paper, Surface Enhanced Raman Scattering(SERS) was utilized to study the interfacial CT property between CuPc and perovskites(single crystal and polycrystalline). The Raman spectra of CuPc adsorbed on the perovskite surface was enhanced. The laser wavelength dependent SERS study indicates that this phenomenon is mainly arising from the CT from the VB band of perovskite to the LUMO band of the CuPc molecules. In comparison, the SERS signal of CuPc molecules adsorbed on a single crystal is much stronger than that on the polycrystalline perovskite. This result indicates that the defect status affects the enhancement ability of the materials. Further study shows that, after the decoration of a thin silver film, the SERS spectra of CuPc on both single crystal and polycrystalline perovskites are further enhanced. The extreme enhancement is not only due to the electromagnetic property of the silver film but also the fact that the SPR of the silver enhances the charge separation of the perovskite, which further promotes the CT process between the substrate and adsorbed molecules. The CT based SERS study shows great potential application value in the field of optoelectronic research.