The integration of a third component in layer-by-layer (LbL) organic photovoltaics (OPVs) effectively modulates the morphology and optoelectronic properties of the photoactive layer. In this study, we demonstrate that the targeted incorporation of IT-Th into both the donor (PM6) and acceptor (eC9) layers markedly enhances device performance. The presence of IT-Th promotes increased crystallinity in the donor material while concurrently mitigating excessive aggregation of the acceptor. The increased open-circuit voltage and short-circuit current density are attributed to energy level alignment and improved vertical phase separation, leading to increased device performance. Transient photovoltage investigations indicate that the morphological features reduce tail states, facilitate the formation of delocalized charges carriers. These findings underscore the critical role of interfacial and structural engineering in advancing the performance of LbL process ternary OPVs.