Organic Nonlinear optical (NLO) crystals hold promise for efficient terahertz (THz) generation, applicable in security screening and manufacturing quality inspection. Existing NLO organic crystals face THz self-absorption issues due to phonon vibration, limiting efficiency. To address this, we propose a novel design strategy introducing additional intermolecular interactions. In this research, we designed and synthesized a series of new organic NLO crystals based on OHQ (2-(4-hydroxystyryl)-1-methylquinolinium) chromophores by introducing fluorine. Ionic crystals with high density are developed by selecting various counter anions with different space-filling characteristics, resulting in diverse molecular ordering. Fluorinated OH-6FQ (6-fluoro-2-(4-hydroxystyryl)-1-methylquinolinium) cations creates additional hydrogen bonds, suppressing phonon vibrations and self_x0002_absorption of the generated THz waves. Notably, new OH-6FQ-TFO crystals containing TFO (4-(trifluoromethoxy)benzenesulfonate) anions which is fluorinated anions based on highly electronegative trifluoromethoxy groups, exhibit F···F intermolecular interactions. Moreover, new fluorinated OH-6FQ-based crystals show higher crystal-density than benchmark crystals. High crystal-density might result in reducing phonon vibration and low absorption coefficient in the THz frequency range. We also developed OH-nXQ-based crystals with halogenated CBS (4-chlorobenzenesulfonate) anions and non-halogenated MBS (4-methoxybenzenesulfonate) anions, which could be expected exhibit high crystal_x0002_density. In addition, OH-nXQ-based crystals from additional hydrogen bonds induced by halogen substituents, it can be expected as high-efficiency THz wave generators. Therefore, molecular engineering through halogen introduction and _x000D_
<br>control of space-filling characteristics may prove a promising strategy for effective THz wave generators, showcasing reduced self-absorption and higher microscopic optical nonlinearity compared to benchmark OHQ-based crystals.
