Influence of the acceptor crystallinity on the open-circuit voltage in PTB7-Th: ITIC organic solar cells

Abstract

The influence of the solution property on both the morphology and the device performance is discussed through various investigation methods based on ITO/ZnO/PTB7-Th: ITIC/M_OO₃/Ag Organic Solar Cells (OSCs). It is found that the solution component plays an important role in the morphology and the crystallinity of the active layers as confirmed by atomic force microscope (AFM) and grazing incident wide-angle X-ray scattering (GIWAXS), resulting in obviously difference in the open-circuit voltage (V_OC) of the devices. The crystallinity of ITIC acceptor in the active layer is further found to correlate with the energy of charge transfer states (CTS) of the devices according to the Electroluminescence (EL) Spectrometry measurements. The CTS energy shift caused by the crystallinity variation is directly related to the enhanced V_OC in this study.