Organic light-emitting transistors (OLETs) are gaining increasing attention as a promising candidate for next-generation display technology. However, due to the limited horizontal charge transport capability in OLETs, enhancing their optical performance remains greatly challenging. In this work, an effective strategy is employed to achieve high-performance OLETs by constructing a two-dimensional molecular-scale passivation layer at the dielectric/channel interface using a promising solution-processed small-molecule material, tetratetracontane (TTC). By controlling the microscopic flows driven by intermolecular interactions near the solution meniscus, molecular self-assembly dynamics are effectively regulated, contributing to a significant transformation in molecular layer stacking mode and enabling the formation of large-area TTC thin films with two-dimensional molecular-scale surface structure and uniform morphology. The introduction of high-quality TTC passivation layer film into the dielectric/channel interface optimizes the film morphologies of overlying channel layer, effectively shields the electrostatic dipole effects at dielectric/channel interface, leading to the synergistic optoelectronic regulation and enhanced optical properties of OLETs. Consequently, high brightness of 10,077.3 cd·m⁻², high external quantum efficiency (EQE) of 20.46%, and low voltage of 15 V are achieved in the lateral OLET. This work presents a promising approach for two-dimensional molecular-scale small molecule interfaces, and provides an effective strategy for achieving high-performance OLET devices.