However, commercially available PLQY standards in the NIR-II window also display very low PLQY values. Taking a widely used NIR-II PLQY standard called IR-26 as an example, its PLQY has been reported to range from 0.05% to 0.50%. Accurate determination of such a low PLQY value is challenging using an absolute method. When using this standard, the measured PLQY values of NIR-II materials can deviate from the actual values by 10 times. On the other hand, researchers use various reference standards, and there may not be a reliable correlation between these standards. This could render the PLQY values reported in different literature completely incomparable. Therefore, developing new NIR-II PLQY standards with reliable PLQY values is an urgent task. In addition, certified NIR-II PLQY standards are valuable tools for validating the performance of integrating sphere setups and the reliability of other ensembles and methods used for measuring PLQY. In this work, we developed a new PLQY standard for NIR-II materials using the THF solution of a NIR-II aggregation-induced emission (AIE) luminogen called TPE-BBT. The resulting transparent solution exhibited an even higher PLQY than the nanoparticle form, reaching 4.17% in the integrating sphere. To the best of our knowledge, this is one of the highest absolute PLQY values reported for organic small-molecule dye solutions. We demonstrated that the THF solution of TPE-BBT exhibited negligible concentration-dependent PLQY changes within the 808-nm absorbance ranging from 0.01 to 0.1 at room temperature, and no aggregation was observed within this range. Using the PLQY value of the TPE-BBT solution as a standard, we successfully calibrated the PLQY for two commercially available NIR-II PLQY standards, namely IR-1061 and IR-26.