Enhancement of vertical phase separation in sequentially deposited organic photovoltaics through the independent processing of additives

Herein, the impact of the independent control of processing additives on vertical phase separation in sequentially deposited (SD) organic photovoltaics (OPVs) and its subsequent effects on charge carrier kinetics at the electron donor-acceptor interface are investigated. The film morphology exhibits notable variations, significantly depending on the layer to which 1,8-diiodooctane (DIO) was applied. Grazing incidence wide-angle X-ray scattering analysis reveals distinctly separated donor/acceptor phases and vertical crystallinity details in SD films. Time-of-flight secondary ion mass spectrometry analysis is employed to obtain component distributions in diverse vertical phase structures of SD films depending on additive control. In addition, nanosecond transient absorption spectroscopy shows that DIO control significantly affects the dynamics of separated charges in SD films. In SD OPVs, DIO appears to act through distinct mechanisms with minimal restriction, depending on the applied layer. This study emphasizes the significance of morphological optimization in improving device performance and underscores the importance of independent additive control in the advancement of OPV technology.