Structural control of organic solar cells based on nonplanar metallophthalocyanine/C60 heterojunctions using organic buffer layers

The systematic variations in structural, optical and electrical properties of lead phthalocyanine (PbPc)-based solar cells with organic buffer layers were investigated. Transition of the PbPc crystal from a monoclinic phase to a triclinic one was observed when the buffer layers were changed. The structural properties of triclinic PbPc grown on the sexithiophene (6T) buffer layer was superior to those of PbPc grown on the other organic substrates. Since the crystal growth of organic layers is dominated by the anisotropic intermolecular interactions at organic hetero-interfaces, the highly oriented 6T buffer layer with the atomically flat morphology promotes the growth of well-ordered PbPc layers. The performance of the organic solar cells (OSCs) was in direct correlation with the structural and electrical properties of the PbPc single layers. The formation of the triclinic phase enhances the spectrum sensitivity at around 890 nm, suggesting the enhancement of the current density of OSCs. Thus, the control of both crystal quality and phase of PbPc layers using a proper organic buffer layer is effective in enhancing the device performance of OSCs.